4,379 results on '"Aoki, H."'
Search Results
2. Exact continuum theory of anti-Klein tunneling in bilayer graphene
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Maksym, P. A. and Aoki, H.
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Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Exact conditions for anti-Klein transmission zeros are found analytically with a 4-component continuum approach which includes trigonal warping. Anti-Klein tunneling occurs at oblique incidence on steps and barriers with soft and hard walls as well as in the known case of normal incidence on a hard step. The necessary energy and angle of incidence depend on the crystallographic orientation of the step or barrier. At normal incidence on an armchair step in unbiased bilayer graphene, anti-Klein tunneling occurs because both the continuum and the tight binding Hamiltonians are invariant under layer and site interchange. At oblique incidence, anti-Klein tunneling is valley-dependent even in the absence of trigonal warping. An experimental arrangement that functions both as a detector of anti-Klein tunneling and a valley polarizer is suggested. There are cases where anti-Klein tunneling occurs in the 4-component theory but not in the 2-component approximation., Comment: 16 pages, 10 figures
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- 2023
3. Sub-cycle multidimensional spectroscopy of strongly correlated materials
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Valmispild, V., Gorelov, E., Eckstein, M., Lichtenstein, A., Aoki, H., Katsnelson, M., Ivanov, M., and Smirnova, O.
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Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Quantum Gases ,Physics - Atomic Physics ,Physics - Optics ,Quantum Physics - Abstract
Strongly correlated solids are extremely complex and fascinating quantum systems, where new states continue to emerge, especially when interaction with light triggers interplay between them. In this interplay, sub-laser-cycle electron response is particularly attractive as a tool for ultrafast manipulation of matter at PHz scale. Here we introduce a new type of non-linear multidimensional spectroscopy, which allows us to unravel the sub-cycle dynamics of strongly correlated systems interacting with few-cycle infrared pulses and the complex interplay between different correlated states evolving on the sub-femtosecond time-scale. We demonstrate that single particle sub-cycle electronic response is extremely sensitive to correlated many-body dynamics and provides direct access to many body response functions. For the two-dimensional Hubbard model under the influence of ultra-short, intense electric field transients, we demonstrate that our approach can resolve pathways of charge and energy flow between localized and delocalized many-body states on the sub-cycle time scale and follow the creation of a highly correlated state surviving after the end of the laser pulse. Our findings open a way towards a regime of imaging and manipulating strongly correlated materials at optical rates, beyond the multi-cycle approach employed in Floquet engineering, with the sub-cycle response being a key tool for accessing many body phenomena., Comment: 10 pages, 4, figures, Methods (5 pages), Supplementary information (4 figures, 4 pages)
- Published
- 2022
4. Complete Spin and Valley Polarization by Total External Reflection from Potential Barriers in Bilayer Graphene and Monolayer Transition Metal Dichalcogenides
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Maksym, P. A. and Aoki, H.
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Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
It is shown that potential barriers in bilayer graphene (BLG) and monolayer transition metal dichalcogenides (TMDs) can split a valley unpolarized incident current into reflected and transmitted currents with opposite valley polarization. Valley asymmetric transmission inevitably occurs because of the low symmetry of the total Hamiltonian and when total external reflection occurs the transmission is 100% valley polarized in BLG and 100% spin and valley polarized in TMDs, except for exponentially small corrections. By adjusting the potential, 100% polarization can be obtained regardless of the crystallographic orientation of the barrier. A valley polarizer can be realized by arranging for a collimated beam of carriers to be incident on a barrier within the range of angles for total external reflection. The transmission coefficients of barriers with a relative rotation of $\pm\pi/3$ are related by symmetry. This allows two barriers to be used to demonstrate that the current is valley polarized. A soft-walled potential is used to model the barrier and the method used to find the transmission coefficients is explained. In the case of monolayer TMDs, a 4-band k.p Hamiltonian is used and the k.p parameters are obtained by fitting to ab-initio band structures., Comment: 21 pages, 16 figures; merged paper and supplemental material; updated references
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- 2019
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5. Physical properties and phase diagram of single crystal REBaMn2O6 (RE = Sm, Eu, Gd, Tb, Dy, and Y)
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Yamada, S., Sagayama, H., Yamazaki, M., Aoki, H., Sugimoto, K., and Arima, T.
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- 2022
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6. Lattice realization of the generalized chiral symmetry in two dimensions
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Kawarabayashi, T., Aoki, H., and Hatsugai, Y.
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Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
While it has been pointed out that the chiral symmetry, which is important for the Dirac fermions in graphene, can be generalized to tilted Dirac fermions as in organic metals, such a generalized symmetry was so far defined only for a continuous low-energy Hamiltonian. Here we show that the generalized chiral symmetry can be rigorously defined for lattice fermions as well. A key concept is a continuous "algebraic deformation" of Hamiltonians, which generates lattice models with the generalized chiral symmetry from those with the conventional chiral symmetry. This enables us to explicitly express zero modes of the deformed Hamiltonian in terms of that of the original Hamiltonian. Another virtue is that the deformation can be extended to non-uniform systems, such as fermion-vortex systems and disordered systems. Application to fermion vortices in a deformed system shows how the zero modes for the conventional Dirac fermions with vortices can be extended to the tilted case., Comment: 11 pages, 10 figures
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- 2016
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7. Aβ Influx into the Blood Evoked by Different Blood Aβ Removal Systems: A Potential Therapy for Alzheimer’s Disease
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Kitaguchi N, Kawaguchi K, Sakata M, Aoki H, Yamazaki K, Kaneko M, Kinomura J, Kato M, Hasegawa M, Suzuki N, Mizuno M, and Yuzawa Y
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amyloid ,blood purification ,extracorporeal system ,polysulfone hemodialyzer ,hexdc ,3d printer ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 ,Neurology. Diseases of the nervous system ,RC346-429 - Abstract
Nobuya Kitaguchi,1 Kazunori Kawaguchi,1 Miwa Sakata,1 Hiroki Aoki,1 Kazunori Yamazaki,1 Megumi Kaneko,1 Jun Kinomura,1 Masao Kato,2 Midori Hasegawa,2 Nobuo Suzuki,3 Masao Mizuno,4 Yukio Yuzawa2 1Faculty of Clinical Engineering, School of Medical Sciences, Fujita Health University, Toyoake, Aichi, 470-1192, Japan; 2Department of Nephrology, School of Medicine, Fujita Health University, Toyoake, Aichi, Japan; 3Chiryu Clinic, Chiryu, Aichi, Japan; 4Mizuno Clinic, Toyoake, Aichi, JapanCorrespondence: Nobuya KitaguchiFaculty of Clinical Engineering, School of Health Sciences, Fujita Health University, 4-8-17, Yuzato, Higashisumiyosi-Ku, Osaka, 546-0013, JapanTel +81-6-4392-7087Fax +81-6-4392-7087Email nkitaguc@fujita-hu.ac.jpPurpose: Amyloid-β (Aβ) is a brain protein that causes Alzheimer’s disease. We have revealed that extracorporeal blood Aβ-removal systems evoked a large Aβ influx into the blood. This study investigated the system that is more effective in evoking Aβ influx.Methods: Aβ removal activities were compared between hexadecyl-alkylated cellulose beads (HexDC) and fragments of polysulfone hollow fibers (PSf-HFs) in mini-columns to eliminate the filtration effect. Then, adsorptive filtration systems were adapted for PSf hemodialyzers to enhance Aβ adsorption on micropores in the wall of hollow fibers. Plasma Aβ concentrations of patients with renal failure were analyzed during treatment with PSf hemodialyzers alone for 8 h or tandemly connected HexDC and PSf hemodialyzers for 4 h.Results: In the in vitro study, Aβ removal efficiency for HexDC was approximately 100% during the 60 min treatment, whereas the removal efficiency for PSf-HF fragments gradually decreased. However, PSf hemodialyzer in adsorptive filtration systems removed Aβs comparably or more than HexDC. Aβ influx into the blood increases time-dependently. Concomitant use of HexDC and PSf hemodialyzer evoked a larger Aβ1– 40 influx than that of PSf hemodialyzer alone. However, Aβ1– 42 influx by PSf hemodialyzer alone was similar to or a little larger than influx by the combined system. Both systems evoked almost doubled Aβ influx than estimated Aβs existing in the normal brain during the 4 h treatment.Conclusion: PSf hemodialyzer alone for a longer period and concomitant use of HexDC and PSf hemodialyzer for a shorter time effectively evoked a larger Aβ influx. To evoke Aβ1– 42 influx, PSf hemodialyzer alone was effective enough. These findings of devices and treatment time may lead to optimal clinical settings for therapy and prevention of Alzheimer’s disease.Keywords: amyloid, blood purification, extracorporeal system, polysulfone hemodialyzer, HexDC, 3D printer
- Published
- 2021
8. Damping of the Collective Amplitude Mode in Superconductors with Strong Electron-Phonon Coupling
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Murakami, Y., Werner, P., Tsuji, N., and Aoki, H.
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Condensed Matter - Superconductivity ,Condensed Matter - Strongly Correlated Electrons - Abstract
We study the effect of strong electron-phonon interactions on the damping of the Higgs amplitude mode in superconductors by means of non-equilibrium dynamical mean-field simulations of the Holstein model. In contrast to the BCS dynamics, we find that the damping of the Higgs mode strongly depends on the temperature, becoming faster as the systen approaches the transition temperature. The damping at low temperatures is well described by a power-law, while near the transition temperature the damping shows exponential-like behavior. We explain this crossover by a temperature-dependent quasiparticle lifetime caused by the strong electron- phonon coupling, which smears the superconducting gap edge and makes the relaxation of the Higgs mode into quasiparticles more efficient at elevated temperatures. We also reveal that the phonon dynamics can soften the Higgs mode, which results in a slower damping., Comment: 7 pages,6 figures
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- 2016
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9. Flat bands in Weaire-Thorpe model and silicene
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Hatsugai, Y., Shiraishi, K., and Aoki, H.
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Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
In order to analytically capture and identify peculiarities in the electronic structure of silicene, Weaire-Thorpe(WT) model, a standard model for treating three-dimensional (3D) silicon, is applied to silicene with the buckled 2D structure. In the original WT model for four hybridized $sp^3$ orbitals on each atom along with inter-atom hopping, the band structure can be systematically examined in 3D, where flat (dispersionless) bands exist as well. For examining silicene, here we re-formulate the WT model in terms of the overlapping molecular-orbital (MO) method which enables us to describe flat bands away from the electron-holesymmetric point. The overlapping MO formalism indeed enables us to reveal an important difference: while in 3D the dipersive bands with cones are sandwiched by doubly-degenerate flat bands, in 2D the dipersive bands with cones are sandwiched by triply-degenerate and non-degenerate (nearly) flat bands, which is consistent with the original band calculation by Takeda and Shiraishi. Thus emerges a picture for why the whole band structure of silicene comprises a pair of dispersive bands with Dirac cones with each of the band touching a nearly flat (narrow) band at $\Gamma$. We can also recognize that, for band engineering, the bonds perpendicular to the atomic plane are crucial, and that a ferromagnetism or structural instabilities are expected if we can shift the chemical potential close to the flat bands., Comment: 13 pages, 3 figures (final version) to appear in NJP
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- 2014
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10. Erratum.
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Klionsky, DJ, Abdelmohsen, K, Abe, A, Abedin, MJ, Abeliovich, H, Arozena, AA, Adachi, H, Adams, CM, Adams, PD, Adeli, K, Adhihetty, PJ, Adler, SG, Agam, G, Agarwal, R, Aghi, MK, Agnello, M, Agostinis, P, Aguilar, PV, Aguirre-Ghiso, J, Airoldi, EM, Ait-Si-Ali, S, Akematsu, T, Akporiaye, ET, Al-Rubeai, M, Albaiceta, GM, Albanese, C, Albani, D, Albert, ML, Aldudo, J, Algül, H, Alirezaei, M, Alloza, I, Almasan, A, Almonte-Beceril, M, Alnemri, ES, Alonso, C, Altan-Bonnet, N, Altieri, DC, Alvarez, S, Alvarez-Erviti, L, Alves, S, Amadoro, G, Amano, A, Amantini, C, Ambrosio, S, Amelio, I, Amer, AO, Amessou, M, Amon, A, An, Z, Anania, FA, Andersen, SU, Andley, UP, Andreadi, CK, Andrieu-Abadie, N, Anel, A, Ann, DK, Anoopkumar-Dukie, S, Antonioli, M, Aoki, H, Apostolova, N, Aquila, S, Aquilano, K, Araki, K, Arama, E, Aranda, A, Araya, J, Arcaro, A, Arias, E, Arimoto, H, Ariosa, AR, Armstrong, JL, Arnould, T, Arsov, I, Asanuma, K, Askanas, V, Asselin, E, Atarashi, R, Atherton, SS, Atkin, JD, Attardi, LD, Auberger, P, Auburger, G, Aurelian, L, Autelli, R, Avagliano, L, Avantaggiati, ML, Avrahami, L, Azad, N, Awale, S, Bachetti, T, Backer, JM, Bae, DH, Bae, JS, Bae, ON, Bae, SH, Baehrecke, EH, Baek, SH, Baghdiguian, S, and Bagniewska-Zadworna, A
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Biochemistry & Molecular Biology ,Biochemistry and Cell Biology - Published
- 2016
11. The role of cellular senescence in aortic dissection
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Nakao, E, primary, Aoki, H, additional, Hashimoto, Y, additional, Majima, R, additional, Hori-Hayashi, M, additional, Ito, S, additional, Ohno-Urabe, S, additional, Furusho, A, additional, Nishida, N, additional, Hirakata, S, additional, and Fukumoto, Y, additional
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- 2023
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12. Effect of Ar–N2 Sputtering Gas on Structure and Tunneling Magnetodielectric Effect in Co–(Si–N) Nanogranular Films
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Uchiyama, T., primary, Cao, Y., additional, Kijima-Aoki, H., additional, Ikeda, K., additional, Kobayashi, N., additional, Ohnuma, S., additional, and Masumoto, H., additional
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- 2023
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13. B cells and immunoglobulins promotes aortic dissection in mice
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Ohno, S, primary, Aoki, H, additional, Furusho, A, additional, Hashimoto, Y, additional, Nakao, E, additional, Shibata, R, additional, Nishida, N, additional, Ito, S, additional, Majima, R, additional, and Fukumoto, Y, additional
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- 2023
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14. EP08.02-10 Clinicopathological Analyses for Predicting Survival After Salvage Surgery for Initially Unresectable Lung Cancer
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Oka, N., primary, Hishida, T., additional, Kaseda, K., additional, Oshiro, Y., additional, Sakurada, A., additional, Sugino, K., additional, Aoki, H., additional, Ishiguro, Y., additional, Imoto, T., additional, Okubo, Y., additional, Masai, K., additional, Asakura, K., additional, Emoto, K., additional, and Asamura, H., additional
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- 2023
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15. Liquefaction hazard evaluation by Swedish weight sounding test
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Kuwano, J., primary, Ogawa, K., additional, Kimura, T., additional, and Aoki, H., additional
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- 2020
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16. Three-orbital study on the orbital distillation effect in the high Tc cuprates
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Sakakibara, H., Suzuki, K., Usui, H., Kuroki, K., Arita, R., Scalapino, D. J., and Aoki, H.
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Condensed Matter - Superconductivity ,Condensed Matter - Materials Science ,Condensed Matter - Strongly Correlated Electrons - Abstract
Our recent study has revealed that the mixture of the dz2 orbital component into the Fermi surface suppresses Tc in the cuprates such as La2CuO4. We have also shown that applying hydrostatic pressure enhances Tc due to smaller mixing of the Cu4s component. We call these the "orbital distillation" effect. In our previous study, the 4s orbital was taken into account through the hoppings in the dx2-y2 sector, but here we consider a model in which of the dx2-y2, dz2 and 4s orbitals are all considered explicitly. The present study reinforces our conclusion that smaller 4s hybridization further enhances Tc., Comment: 4 pages, 2 figures, submitted as a proceeding of ISS2012(Tokyo)
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- 2012
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17. Magnetic field controlled vacuum charge in graphene quantum dots with a mass gap
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Maksym, P. A. and Aoki, H.
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Condensed Matter - Mesoscale and Nanoscale Physics ,Physics - Atomic Physics ,Quantum Physics - Abstract
The effect of a magnetic field on the charged vacuum is investigated. The field dependence of the energy levels causes jumps in the total vacuum charge that occur whenever an energy level crosses the Fermi level and this leads to re-entrant cycles of vacuum charging and discharging. In atomic systems these effects require astrophysical magnetic fields of around 10^8 T but in graphene with a mass gap they occur in laboratory fields of about 1 T or lower. It is suggested that an electrostatic graphene quantum dot defined by a gate electrode provides a solid state model of the as yet unobserved charged vacuum as well as a model of an atomic system in an extreme astrophysical environment. Phase diagrams are computed to show how the total vacuum charge depends on the confining potential strength and applied magnetic field. In addition the field dependence of the vacuum charge density is investigated and experimental consequences are discussed., Comment: 5 pages, 4 figures
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- 2012
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18. Chiral symmetry and its manifestation in optical responses in graphene: interaction and multi-layers
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Hatsugai, Y., Morimoto, T., Kawarabayashi, T., Hamamoto, Y., and Aoki, H.
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Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Strongly Correlated Electrons - Abstract
Chiral symmetry, fundamental in the physics of graphene, guarantees the existence of topologically stable doubled Dirac cones and anomalous behaviors of the zero-energy Landau level in magnetic fields. The crucial role is inherited in the optical responses and many-body physics in graphene, which are explained in this paper. We also give an overview of multilayer graphene from the viewpoint of the optical properties and their relation with the chiral symmetry., Comment: 21 pages, 9 figures
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- 2012
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19. Fast split operator method for computation of time dependent quantum states of bilayer graphene in a magnetic field
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Maksym, P.A. and Aoki, H.
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- 2019
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20. Chiral symmetry and fermion doubling in the zero-mode Landau levels of massless Dirac fermions with disorder
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Kawarabayashi, T., Honda, T., Aoki, H., and Hatsugai, Y.
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Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
The effect of disorder on the Landau levels of massless Dirac fermions is examined for the cases with and without the fermion doubling. To tune the doubling a tight-binding model having a complex transfer integral is adopted to shift the energies of two Dirac cones, which is theoretically proposed earlier and realizable in cold atoms in an optical lattice. In the absence of the fermion doubling, the $n=0$ Landau level is shown to exhibit an anomalous sharpness even if the disorder is uncorrelated in space (i.e., large K-K' scattering). This anomaly occurs when the disorder respects the chiral symmetry of the Dirac cone., Comment: 3 pages, 2 figures, Proceedings of ICPS 2012, typos corrected, one sentence added in section II
- Published
- 2012
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21. Terahertz dynamics of a topologically protected state: quantum Hall effect plateaus near cyclotron resonance in a GaAs/AlGaAs heterojunction
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Stier, A. V., Ellis, C. T., Zhang, H., Eason, D., Strasser, G., Morimoto, B. D. McCombe T., Aoki, H., and Cerne, J.
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Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
We measure the Hall conductivity of a two-dimensional electron gas formed at a GaAs/AlGaAs heterojunction in the terahertz regime close to the cyclotron resonance frequency by employing a highly sensitive Faraday rotation method coupled with electrical gating of the sample to change the electron density. We observe clear plateau-and step-like features in the Faraday rotation angle vs. electron density and magnetic field (Landau-level filling factor), which are the high frequency manifestation of quantum Hall plateaus - a signature of topologically protected edge states. The results are compared to a recent dynamical scaling theory., Comment: 18 pages, 3 figures
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- 2011
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22. Origin of the material dependence of $T_c$ in the single-layered cuprates
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Sakakibara, H., Usui, H., Kuroki, K., Arita, R., and Aoki, H.
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Condensed Matter - Superconductivity ,Condensed Matter - Materials Science ,Condensed Matter - Strongly Correlated Electrons - Abstract
In order to understand the material dependence of $T_c$ within the single-layered cuprates, we study a two-orbital model that considers both $d_{x^2-y^2}$ and $d_{z^2}$ orbitals. We reveal that a hybridization of $d_{z^2}$ on the Fermi surface substantially affects $T_c$ in the cuprates, where the energy difference $\Delta E$ between the $d_{x^2-y2}$ and $d_{z^2}$ orbitals is identified to be the key parameter that governs both the hybridization and the shape of the Fermi surface. A smaller $\Delta E$ tends to suppress $T_c$ through a larger hybridization, whose effect supersedes the effect of diamond-shaped (better-nested) Fermi surface. The mechanism of the suppression of d-wave superconductivity due to $d_{z^2}$ orbital mixture is clarified from the viewpoint of the ingredients involved in the Eliashberg equation, i.e., the Green's functions and the form of the pairing interaction described in the orbital representation. The conclusion remains qualitatively the same if we take a three-orbital model that incorporates Cu 4s orbital explicitly, where the 4s orbital is shown to have an important effect of making the Fermi surface rounded. We have then identified the origin of the material and lattice-structure dependence of $\Delta E$, which is shown to be determined by the energy difference $\Delta E_d$ between the two Cu3d orbitals (primarily governed by the apical oxygen height), and the energy difference $\Delta E_p$ between the in-plane and apical oxygens (primarily governed by the interlayer separation $d$).
- Published
- 2011
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23. Chiral Symmetry and Electron-Electron Interaction in Many-Body Gap Formation in Graphene
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Hamamoto, Y., Hatsugai, Y., and Aoki, H.
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Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
We study a many-body ground state of graphene in perpendicular magnetic fields. Chiral symmetry in graphene enables us to determine the many-body ground state, which turns out to be a doubly degenerate chiral condensate for the half-filled (undoped) case. In the ground state a prominent charge accumulation emerges along zigzag edges. We also show that gapless excitations are absent despite the presence of the robust edge modes, which is consistent with the Chern number C = 0., Comment: 4 pages, 3 figures, proceeding of 26th International Conference on Low Temperature Physics (LT26)
- Published
- 2011
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24. Experiments to investigate the effects of radiative cooling on plasma jet collimation
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Gregory, C. D., Diziere, A., Aoki, H., Besio, M., Bouquet, S., Falize, E., Ide, T., Loupias, B., Michaut, C., Morita, T., Pikuz Jr., S. A., Ravasio, A., Kuramtisu, Y., Sakawa, Y., Takabe, H., Tanji, H., Woolsey, N. C., and Koenig, M.
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Physics - Plasma Physics - Abstract
Preliminary experiments have been performed to investigate the effects of radiative cooling on plasma jets. Thin (3 um - 5 um) conical shells were irradiated with an intense laser, driving jets with velocities > 100 km/s. Through use of different target materials - aluminium, copper and gold - the degree of radiative losses was altered, and their importance for jet collimation investigated. A number of temporally resoved optical diagnostics was used, providing information about the jet evolution. Gold jets were seen to be narrower than those from copper targets, while aluminium targets produced the least collimated flows., Comment: Presented at the 8th High Energy Density Laboratory Astrophysics conference, March 15th - 18th, Caltech, CA, USA
- Published
- 2010
25. Manipulation of the Dirac cones and the anomaly in the graphene related quantum Hall effect
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Watanabe, H, Hatsugai, Y, and Aoki, H
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Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
The quantum Hall effect in graphene is regarded to be involving half-integer topological numbers associated with the massless Dirac particle, this is usually not apparent due to the doubling of the Dirac cones. Here we theoretically consider two classes of lattice models in which we manipulate the Dirac cones with either (a) two Dirac points that have mutually different energies, or (b) multiple Dirac cones having different Fermi velocities. We have shown, with an explicit calculation of the topological (Chern) number for case (a) and with an adiabatic argument for case (b) that the results are consistent with the picture that a single Dirac fermion contributes the half-odd integer series (... -3/2, -1/2, 1/2, 3/2, ...) to the Hall conductivity when the Fermi energy traverses the Landau levels., Comment: 4 pages, 5 figures, proceedings for HMF-19
- Published
- 2010
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26. Phase-separated Ferromagnetism in Spin-imbalanced Fermi Atoms Loaded on an Optical Ladder: a DMRG study
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Okumura, M., Yamada, S., Machida, M., and Aoki, H.
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Condensed Matter - Quantum Gases - Abstract
We consider repulsively-interacting cold fermionic atoms loaded on an optical ladder lattice in a trapping potential. The density-matrix renormalization-group method is used to numerically calculate the ground state for systematically varied values of interaction U and spin imbalance p in the Hubbard model on the ladder. The system exhibits rich structures, where a fully spin polarized phase, spatially separated from other domains in the trapping potential, appears for large enough U and p. The phase-separated ferromagnetism can be captured as a real-space image of the energy gap between the ferromagnetic and other states arising from a combined effect of Nagaoka's ferromagnetism extended to the ladder and the density dependence of the energy separation between competing states. We also predict how to maximize the ferromagnetic region.
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- 2010
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27. Proposal for a magnetic field induced graphene dot
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Maksym, P. A., Roy, M., Craciun, M. F., Yamamoto, M., Tarucha, S., and Aoki, H.
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Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Quantum dots induced by a strong magnetic field applied to a single layer of graphene in the perpendicular direction are investigated. The dot is defined by a model potential which consists of a well of depth $\Delta V$ relative to a flat asymptotic part and quantum states formed from the zeroth Landau level are considered. The energy of the dot states cannot be lower than $-\Delta V$ relative to the asymptotic potential. Consequently, when $\Delta V$ is chosen to be about half of the gap between the zeroth and first Landau levels, the dot states are isolated energetically in the gap between Landau level 0 and Landau level -1. This is confirmed with numerical calculations of the magnetic field dependent energy spectrum and the quantum states. Remarkably, an antidot formed by reversing the sign of $\Delta V$ also confines electrons but in the energy region between Landau level 0 and Landau level +1. This unusual behaviour gives an unambiguous signal of the novel physics of graphene quantum dots., Comment: 4 pages, 2 figures
- Published
- 2010
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28. 4f-derived Fermi Surfaces of CeRu2(Si[1-x]Ge[x])2 near the Quantum Critical Point: Resonant Soft X-ray ARPES Study
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Okane, T., Ohkochi, T., Takeda, Y., Fujimori, S. -i., Yasui, A., Saitoh, Y., Yamagami, H., Fujimori, A., Matsumoto, Y., Sugi, M., Kimura, N., Komatsubara, T., and Aoki, H.
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Condensed Matter - Strongly Correlated Electrons - Abstract
Angle-resolved photoelectron spectroscopy in the Ce 3d-4f excitation region was measured for the paramagnetic state of CeRu2Si2, CeRu2(Si0.82Ge0.18)2, and LaRu2Si2 to investigate the changes of the 4$f$ electron Fermi surfaces around the quantum critical point. While the difference of the Fermi surfaces between CeRu2Si2 and LaRu2Si2 was experimentally confirmed, a strong 4f-electron character was observed in the band structures and the Fermi surfaces of CeRu2Si2 and CeRu2(Si0.82Ge0.18)2, consequently indicating a delocalized nature of the 4$f$ electrons in both compounds. The absence of Fermi surface reconstruction across the critical composition suggests that SDW quantum criticality is more appropriate than local quantum criticality in CeRu2(Si[1-x]Ge[x])2., Comment: 4 pages, 5 figures
- Published
- 2009
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29. Anisotropy in spatial order-disorder transformations and the vortex lattice symmetry transition in $YNi_2B_2C$ and $LuNi_2B_2C$
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Jaiswal-Nagar, D., Isshiki, T., Kimura, N., Aoki, H., Takeya, H., Ramakrishnan, S., and Grover, A. K.
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Condensed Matter - Superconductivity - Abstract
Explorations of the order-disorder transformation in vortex matter in single crystals of tetragonal structured (c/a $\sim$3) borocarbide superconductors, $YNi_2B_2C$ and $LuNi_2B_2C$, reveal that vortex arrays experience different effective pinning in different crystallographic directions. We surmise that correlation exists between the large anisotropy in effective pinning/disorder and the differences in the (local) symmetry transition from rhombohedral to (quasi) square vortex lattice(VL). For field along high symmetry directions, like, c-axis and ab-basal plane, the VL symmetry is close to square and the ordered state spans a large field interval. When the field is turned away from the c-axis towards ab-plane, at intermediate angles, the region of ordered state shrinks, in response to enhancement in effective pinning. At such intermediate angles the symmetry of the VL would be far from ideal triangular or square., Comment: 6 pages, 5 figures (Accepted in Euro Phys. Letts.)
- Published
- 2008
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30. Accurate Model of a Vertical Pillar Quantum Dot
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Maksym, P. A., Nishi, Y., Austing, D. G., Hatano, T., Kouwenhoven, L. P., Aoki, H., and Tarucha, S.
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Materials Science - Abstract
An accurate model of a vertical pillar quantum dot is described. The full three dimensional structure of the device containing the dot is taken into account and this leads to an effective two dimensional model in which electrons move in the two lateral dimensions, the confinement is parabolic and the interaction potential is very different from the bare Coulomb potential. The potentials are found from the device structure and a few adjustable parameters. Numerically stable calculation procedures for the interaction potential are detailed and procedures for deriving parameter values from experimental addition energy and chemical potential data are described. The model is able to explain magnetic field dependent addition energy and chemical potential data for an individual dot to an accuracy of about 5%, the accuracy level needed to determine ground state quantum numbers from experimental transport data. Applications to excited state transport data are also described., Comment: 14 pages, 6 figures
- Published
- 2008
31. In-plane shear strength characteristics of masonry walls with varying mortar types and aspect ratios
- Author
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Aoki, T., primary, Shrestha, K.C., additional, Nonaka, U., additional, and Aoki, H., additional
- Published
- 2020
- Full Text
- View/download PDF
32. Topological aspects of graphene: Dirac fermions and the bulk-edge correspondence in magnetic fields
- Author
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Hatsugai, Y., Fukui, T., and Aoki, H.
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
We discuss topological aspects of electronic properties of graphene, including edge effects, with the tight-binding model on a honeycomb lattice and its extensions to show the following: (i) Appearance of the pairn of massless Dirac dispersions, which is the origin of anomalous properties including a peculiar quantum Hall effect (QHE), is not accidental to honeycomb, but is rather generic for a class of two-dimensional lattices that interpolate between square and $\pi$-flux lattices. Persistence of the peculiar QHE is interpreted as a topological stability. (ii) While we have the massless Dirac dispersion only around E=0, the anomalous QHE associated with the Dirac cone unexpectedly persists for a wide range of the chemical potential. The range is bounded by van Hove singularities, at which we predict a transition to the ordinary fermion behavior acompanied by huge jumps in the QHE with a sign change. (iii) For edges we establish a coincidence between the quantum Hall effect in the bulk and the quantum Hall effect for the edge states, which is a manifestation of the topological bulk-edge correspondence. We have also explicitly shown that the E=0 edge states in honeycomb in zero magnetic field persist in magnetic field., Comment: 8 pages, 5 figures, proceeding of the graphene conference at MPIPKS Dresden, Sep. 25-Oct.1, 2006
- Published
- 2007
- Full Text
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33. Topological analysis of the quantum Hall effect in graphene: Dirac-Fermi transition across van Hove singularities and the edge vs bulk quantum numbers
- Author
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Hatsugai, Y., Fukui, T., and Aoki, H.
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Inspired by a recent discovery of a peculiar integer quantum Hall effect (QHE) in graphene, we study QHE on a honeycomb lattice in terms of the topological quantum number, with two-fold interests: First, how the zero-mass Dirac QHE around the center of the tight-binding band crosses over to the ordinary finite-mass fermion QHE around the band edges. Second, how the bulk QHE is related with the edge QHE for the entire spectrum including Dirac and ordinary behaviors. We find the following: (i) The zero-mass Dirac QHE persists up to the van Hove singularities, at which the ordinary fermion behavior abruptly takes over. Here a technique developed in the lattice gauge theory enabled us to calculate the behavior of the topological number over the entire spectrum. This result indicates a robustness of the topological quantum number, and should be observable if the chemical potential can be varied over a wide range in graphene. (ii) To see if the honeycomb lattice is singular in producing the anomalous QHE, we have systematically surveyed over square-honeycomb-$\pi$-flux lattices, which is scanned by introducing a diagonal transfer $t'$. We find that the massless Dirac QHE forms a critical line, that is, the presence of Dirac cones in the Brillouin zone is preserved by the inclusion of $t'$ and the Dirac region sits side by side with ordinary one persists all through the transformation. (iii) We have compared the bulk QHE number obtained by an adiabatic continuity of the Chern number across transformation and numerically obtained edge QHE numbers calculated from the whole energy spectra for sample with edges, which shows that the bulk QHE number coincides, as in ordinary lattices, with the edge QHE number throughout the lattice transformation., Comment: Its pdf file with high quality figures is obtained from http://pothos.t.u-tokyo.ac.jp/Lab/Research/preprints/TopoQHE_honey.pdf
- Published
- 2006
34. Transitions between electron-molecule states in electrostatic quantum dots
- Author
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Maksym, P. A. and Aoki, H.
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter - Strongly Correlated Electrons - Abstract
Intermediate spin states that occur in electrostatic dots in the magnetic field regime just beyond the maximum density droplet are investigated. The 5-electron system is studied with exact diagonalization and group theory. The results indicate that the intermediate spin states are mixed symmetry states with a superposition of 5- and 4-fold electron-molecule configurations. A superposition of 5- and 4-fold correlation functions is found to reproduce the exact mixed symmetry pair correlation function to around 2%., Comment: 4 pages, 3 figures
- Published
- 2006
- Full Text
- View/download PDF
35. Intermediate Low Spin States in a Few-electron Quantum Dot in the $\nu\le 1$ Regime
- Author
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Nishi, Y., Maksym, P. A., Austing, D. G., Hatano, T., Kouwenhoven, L. P., Aoki, H., and Tarucha, S.
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
We study the effects of electron-electron interactions in a circular few-electron vertical quantum dot in such a strong magnetic field that the filling factor $\nu\le 1$. We measure excitation spectra and find ground state transitions beyond the maximum density droplet ($\nu=1$) region. We compare the observed spectra with those calculated by exact diagonalization to identify the ground state quantum numbers, and find that intermediate low-spin states occur between adjacent spin-polarized magic number states., Comment: 4 pages, 4 figures
- Published
- 2005
- Full Text
- View/download PDF
36. Development of high-polarization Fe/Ge neutron polarizing supermirror: Possibility of fine-tuning of scattering length density in ion beam sputtering
- Author
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Maruyama, R., Yamazaki, D., Akutsu, K., Hanashima, T., Miyata, N., Aoki, H., Takeda, M., and Soyama, K.
- Published
- 2018
- Full Text
- View/download PDF
37. Electronic structure of an electron on the gyroid surface, a helical labyrinth
- Author
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Koshino, M. and Aoki, H.
- Subjects
Condensed Matter - Other Condensed Matter - Abstract
Previously reported formulation for electrons on curved periodic surfaces is used to analyze the band structure of an electron bound on the gyroid surface (the only triply-periodic minimal surface that has screw axes). We find that an effect of the helical structure appears as the bands multiply sticking together on the Brillouin zone boundaries. We elaborate how the band sticking is lifted when the helical and inversion symmetries of the structure are degraded. We find from this that the symmetries give rise to prominent peaks in the density of states., Comment: RevTeX, 4 pages, 6 figures
- Published
- 2004
- Full Text
- View/download PDF
38. Structure and magnetism in nanocrystalline Ca(La)B$_6$ films
- Author
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Sakuraba, Y., Kato, H., Sato, F., Miyazaki, T., Kimura, N., and Aoki, H.
- Subjects
Condensed Matter - Materials Science - Abstract
Nanocrystalline films of La-doped CaB$_6$ have been fabricated by using a rf-magnetron sputtering. Lattice expansion of up to 6% with respect to the bulk value was observed along the direction perpendicular to the film plane, which arises from the trapping of Ar gas into the film. Large ferromagnetic moment of 3 ~ 4 Bohr magneton per La has been observed in some La-doped films only when the lattice expansion rate is larger than 2.5%., Comment: 2 pages, 2 figures, to appear in J. Magn. Magn. Mater
- Published
- 2004
- Full Text
- View/download PDF
39. Field-angle Dependence of the Zero-Energy Density of States in the Unconventional Heavy-Fermion Superconductor CeCoIn5
- Author
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Aoki, H., Sakakibara, T., Shishido, H., Settai, R., Onuki, Y., Miranovic, P., and Machida, K.
- Subjects
Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Superconductivity - Abstract
Field-angle dependent specific heat measurement has been done on the heavy-fermion superconductor CeCoIn5 down to ~ 0.29 K, in a magnetic field rotating in the tetragonal c-plane. A clear fourfold angular oscillation is observed in the specific heat with the minima (maxima) occurring along the [100] ([110]) directions. Oscillation persists down to low fields H << Hc2, thus directly proving the existence of gap nodes. The results indicate that the superconducting gap symmetry is most probably of dxy type., Comment: 8 pages, 3 figures, to be published in J. Phys. Condens. Matter
- Published
- 2003
- Full Text
- View/download PDF
40. Electronic Structure of B-2$p\sigma$ and $p\pi$ States in MgB$_2$, AlB$_2$ and ZrB$_2$ Single Crystals
- Author
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Nakamura, J., Nasubida, S., Kabasawa, E., Yamazaki, H., Yamada, N., Kuroki, K., Watanabe, M., Oguchi, T., Lee, S., Yamamoto, A., Tajima, S., Umeda, Y., Minakawa, S., Kimura, N., Aoki, H., Otani, S., Shin, S., Callcott, T. A., Ederer, D. L., Denlinger, J. D., and Perera, R. C. C.
- Subjects
Condensed Matter - Superconductivity - Abstract
The effect of electron correlation (EC) on the electronic structure in MgB$_2$, AlB$_2$ and ZrB$_2$, is studied by examining the partial density of states (PDOS) of B-2$p\sigma$ and $p\pi$ orbitals using the polarization dependence of x-ray emission and absorption spectra. The discrepancies between observed and calculated PDOSs cannot be attributed to EC effects. The present results suggest that the EC effect is less than the experimental error ($\sim$ 0.2 eV), which indirectly supports a scenario that electron-phonon interaction plays an essential role in the occurrence of superconductivity., Comment: to appear in Phys. Rev. B
- Published
- 2003
- Full Text
- View/download PDF
41. Electronic structure of periodic curved surfaces -- continuous surface versus graphitic sponge
- Author
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Aoki, H., Koshino, M., Takeda, D., Morise, H., and Kuroki, K.
- Subjects
Condensed Matter - Materials Science - Abstract
We investigate the band structure of electrons bound on periodic curved surfaces. We have formulated Schr\"{o}dinger's equation with the Weierstrass representation when the surface is minimal, which is numerically solved. Bands and the Bloch wavefunctions are basically determined by the way in which the ``pipes'' are connected into a network, where the Bonnet(conformal)-transformed surfaces have related electronic strucutres. We then examine, as a realisation of periodic surfaces, the tight-binding model for atomic networks (``sponges''), where the low-energy spectrum coincides with those for continuous curved surfaces., Comment: 4 pages
- Published
- 2003
- Full Text
- View/download PDF
42. Superconductivity in repulsive electron systems having three-dimensional disconnected Fermi surfaces
- Author
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Onari, S., Arita, R., Kuroki, K., and Aoki, H.
- Subjects
Condensed Matter - Superconductivity - Abstract
The idea of raising Tc in the spin-fluctuation mediated superconductivity on disconnected Fermi surfaces with the gap function changing sign across but not within the Fermi pockets, proposed by Kuroki and Arita for two dimensions (2D), is here extended to three-dimensional (3D) systems. Two typical cases of 3D disconnected Fermi surfaces (stacked bond-alternating lattice and stacked ladder layers) are considered. By solving Eliashberg's equation for Green's function obtained with the fluctuation exchange approximation (FLEX) for the repulsive Hubbard model on these structures, we have shown that Tc can indeed reach O(0.01t), which is almost an order of magnitude higher than in ordinary 3D cases and similar to those for the best case found in 2D. The key factor found here for the favorable condition for the superconductivity on disconnected Fermi surfaces is that the system should be quasi-low dimensional, and the peak in the spin susceptibility should be appropriately "blurred"., Comment: 8 pages, 12 figures
- Published
- 2003
- Full Text
- View/download PDF
43. Duality and integer quantum Hall effect in isotropic 3D crystals
- Author
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Koshino, M. and Aoki, H.
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
We show here a series of energy gaps as in Hofstadter's butterfly, which have been shown to exist by Koshino et al [Phys. Rev. Lett. 86, 1062 (2001)] for anisotropic three-dimensional (3D) periodic systems in magnetic fields $\Vec{B}$, also arise in the isotropic case unless $\Vec{B}$ points in high-symmetry directions. Accompanying integer quantum Hall conductivities $(\sigma_{xy}, \sigma_{yz}, \sigma_{zx})$ can, surprisingly, take values $\propto (1,0,0), (0,1,0), (0,0,1)$ even for a fixed direction of $\Vec{B}$ unlike in the anisotropic case. We can intuitively explain the high-magnetic field spectra and the 3D QHE in terms of quantum mechanical hopping by introducing a ``duality'', which connects the 3D system in a strong $\Vec{B}$ with another problem in a weak magnetic field $(\propto 1/B)$., Comment: 7 pages, 6 figures
- Published
- 2002
- Full Text
- View/download PDF
44. Resistivity, Hall effect and Shubnikov-de Haas oscillations in CeNiSn
- Author
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Terashima, T., Terakura, C., Uji, S., Aoki, H., Echizen, Y., and Takabatake, T.
- Subjects
Condensed Matter - Strongly Correlated Electrons - Abstract
The resistivity and Hall effect in CeNiSn are measured at temperatures down to 35 mK and in magnetic fields up to 20 T with the current applied along the {\it b} axis. The resistivity at zero field exhibits quadratic temperature dependence below $\sim$0.16 K with a huge coefficient of the $T^2$ term (54 $\mu$$\Omega$cm/K$^2$). The resistivity as a function of field shows an anomalous maximum and dip, the positions of which vary with field directions. Shubnikov-de Haas (SdH) oscillations with a frequency {\it F} of $\sim$100 T are observed for a wide range of field directions in the {\it ac} and {\it bc} planes, and the quasiparticle mass is determined to be $\sim$10-20 {\it m}$_e$. The carrier density is estimated to be $\sim10^{-3}$ electron/Ce. In a narrow range of field directions in the {\it ac} plane, where the magnetoresistance-dip anomaly manifests itself clearer than in other field directions, a higher-frequency ($F=300\sim400\text{T}$) SdH oscillation is found at high fields above the anomaly. This observation is discussed in terms of possible field-induced changes in the electronic structure., Comment: 15 pages, 5 figures, to appear in Phys. Rev. B (15 Sept. 2002 issue)
- Published
- 2002
- Full Text
- View/download PDF
45. Tomography of pairing symmetry from magnetotunneling spectroscopy -- a case study for quasi-1D organic superconductors
- Author
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Tanuma, Y., Kuroki, K., Tanaka, Y., Arita, R., Kashiwaya, S., and Aoki, H.
- Subjects
Condensed Matter - Superconductivity ,Condensed Matter - Strongly Correlated Electrons - Abstract
We propose that anisotropic $p$-, $d$-, or $f$-wave pairing symmetries can be distinguished from a tunneling spectroscopy in the presence of magnetic fields, which is exemplified here for a model organic superconductor ${(TMTSF)}_{2}X$. The shape of the Fermi surface (quasi-one-dimensional in this example) affects sensitively the pairing symmetry, which in turn affects the shape (U or V) of the gap along with the presence/absence of the zero-bias peak in the tunneling in a subtle manner. Yet, an application of a magnetic field enables us to identify the symmetry, which is interpreted as an effect of the Doppler shift in Andreev bound states., Comment: 4 papegs, 4 figures
- Published
- 2002
- Full Text
- View/download PDF
46. Orbifold Matrix Model
- Author
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Aoki, H., Iso, S., and Suyama, T.
- Subjects
High Energy Physics - Theory - Abstract
We study a matrix model describing type IIB superstring in orbifold backgrounds. We particularly consider a {\bf C}^3/{\bf Z}_3 orbifold model whose six dimensional transverse space is orbifolded by {\bf Z}_3 discrete symmetry. This model is chiral and has d=4 {\cal N}=1 supersymmetry of Yang-Mills type as well as an inhomogeneous supersymmetry specific to matrix models. We calculate one-loop effective action around some backgrounds, and the result can be interpreted as interactions mediated by massless particles in IIB supergravity in orbifold background, if the background is in the Higgs branch. If the background is in the Coulomb branch, the dynamics is governed by the reduced model of d=4 super Yang-Mills theory, which might be interpreted as exchange of massless particles in the twisted sector. But the perturbative calculation cannot reproduce the supergravity result. We also show that this model with a large Higgs vacuum expectation value becomes IIB (IKKT) matrix model., Comment: 23 pages, references added
- Published
- 2002
- Full Text
- View/download PDF
47. The Magnetic Phase Diagram and the Pressure and Field Dependence of the Fermi Surface in UGe$_2$
- Author
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Terashima, T., Matsumoto, T., Terakura, C., Uji, S., Kimura, N., Endo, M., Komatsubara, T., Aoki, H., and Maezawa, K.
- Subjects
Condensed Matter - Strongly Correlated Electrons ,Condensed Matter - Superconductivity - Abstract
The ac susceptibility and de Haas-van Alphen (dHvA) effect in UGe$_2$ are measured at pressures {\it P} up to 17.7 kbar for the magnetic field {\it B} parallel to the {\it a} axis, which is the easy axis of magnetization. Two anomalies are observed at {\it B$_x$}({\it P}) and {\it B}$_m$({\it P}) ({\it B$_x$} $>$ {\it B}$_m$ at any {\it P}), and the {\it P}-{\it B} phase diagram is presented. The Fermi surface and quasiparticle mass are found to vary smoothly with pressure up to 17.7 kbar unless the phase boundary {\it B$_x$}({\it P}) is crossed. The observed dHvA frequencies may be grouped into three according to their pressure dependences, which are largely positive, nearly constant or negative. It is suggested that the quasiparticle mass moderately increases as the boundary {\it B$_x$}({\it P}) is approached. DHvA effect measurements are also performed across the boundary at 16.8 kbar., Comment: to be published in Phys. Rev. B
- Published
- 2002
- Full Text
- View/download PDF
48. Phase Diagram for the Hofstadter butterfly and integer quantum Hall effect in three dimensions
- Author
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Koshino, M., Aoki, H., Osada, T., Kuroki, K., and Kagoshima, S.
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
We give a perspective on the Hofstadter butterfly (fractal energy spectrum in magnetic fields), which we have shown to arise specifically in three-dimensional(3D) systems in our previous work. (i) We first obtain the `phase diagram' on a parameter space of the transfer energies and the magnetic field for the appearance of Hofstadter's butterfly spectrum in anisotropic crystals in 3D. (ii) We show that the orientation of the external magnetic field can be arbitrary to have the 3D butterfly. (iii) We show that the butterfly is beyond the semiclassical description. (iv) The required magnetic field for a representative organic metal is estimated to be modest ($\sim 40$ T) if we adopt higher Landau levels for the butterfly. (v) We give a simpler way of deriving the topological invariants that represent the quantum Hall numbers (i.e., two Hall conductivity in 3D, $\sigma_{xy}, \sigma_{zx}$, in units of $e^2/h$)., Comment: 8 pages, 8 figures, eps versions of the figures will be sent on request to koshino@cms.phys.s.u-tokyo.ac.jp
- Published
- 2001
- Full Text
- View/download PDF
49. Field-Induced SDW and Butterfly Spectrum in Three Dimensions
- Author
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Koshino, M., Aoki, H., and Osada, T.
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
Landau's quantization for incompletely nested Fermi surfaces is known to give rise to magnetic-field-induced spin-density waves(FISDW) in two-dimensional organic metals. Here we show that three-dimensional(3D) systems can have 3D-specific series of FISDW phases as energetically stable states, for which we clarify how and why they appear as the magnetic field is tilted. Each phase is characterized by quantized Hall effect for each of $\sigma_{xy}$ and $\sigma_{zx}$ that reside on a fractal spectrum like Hofstadter's butterfly., Comment: 4 pages, 4 figures, eps versions of the figures will be sent on request to koshino@cms.phys.s.u-tokyo.ac.jp
- Published
- 2001
- Full Text
- View/download PDF
50. Electronic structure of periodic curved surfaces -- topological band structure
- Author
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Aoki, H., Koshino, M., Takeda, D., and Morise, H.
- Subjects
Condensed Matter - Materials Science - Abstract
Electronic band structure for electrons bound on periodic minimal surfaces is differential-geometrically formulated and numerically calculated. We focus on minimal surfaces because they are not only mathematically elegant (with the surface characterized completely in terms of "navels") but represent the topology of real systems such as zeolites and negative-curvature fullerene. The band structure turns out to be primarily determined by the topology of the surface, i.e., how the wavefunction interferes on a multiply-connected surface, so that the bands are little affected by the way in which we confine the electrons on the surface (thin-slab limit or zero thickness from the outset). Another curiosity is that different minimal surfaces connected by the Bonnet transformation (such as Schwarz's P- and D-surfaces) possess one-to-one correspondence in their band energies at Brillouin zone boundaries., Comment: 6 pages, 8 figures, eps files will be sent on request to aoki@phys.s.u-tokyo.ac.jp
- Published
- 2001
- Full Text
- View/download PDF
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