24 results on '"Li, Lee"'
Search Results
2. 3D Dirac semimetal Cd3As2 : A review of material properties
- Author
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Milan Orlita, I. Crassee, Raman Sankar, Wei-Li Lee, and Ana Akrap
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Graphene ,Dirac (software) ,Cadmium arsenide ,Crystal growth ,02 engineering and technology ,Crystal structure ,021001 nanoscience & nanotechnology ,01 natural sciences ,Semimetal ,law.invention ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,chemistry ,law ,0103 physical sciences ,General Materials Science ,010306 general physics ,0210 nano-technology ,Material properties ,Electronic band structure - Abstract
Cadmium arsenide is a time-honored material within condensed matter physics, with the first investigations dating back to the thirties. Nowadays, after theorists predicted a pair of symmetry-protected three-dimensional Dirac cones in its band structure, cadmium arsenide is going through an intense revival. Cadmium arsenide is now thought of as a three-dimensional analogue of graphene. Several experimental studies showed compelling evidence of conical bands in this material, revealing a number of interesting properties and phenomena. To interpret them correctly, a detailed understanding of the basic material parameters has become even more important than before. To this end, the authors extensively review the past and current knowledge of cadmium arsenide. They start with the crystal lattice properties, and continue with the technological aspects of its crystal growth. This is followed by a discussion of the theoretical and experimental results, leading to different possible views of this material's electronic bands.
- Published
- 2018
3. Energy scale of Dirac electrons in Cd3As2
- Author
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Gerard Martinez, Raman Sankar, J. Debray, Serguei Tchoumakov, M. Hakl, Jiří Novák, Clément Faugeras, A. Nateprov, Benjamin A. Piot, I. Crassee, Wei-Li Lee, Ana Akrap, Marek Potemski, Ondřej Caha, Milan Orlita, Frederic Teppe, Mark Oliver Goerbig, Ernest Arushanov, Laboratoire national des champs magnétiques intenses - Grenoble (LNCMI-G ), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire Charles Coulomb (L2C), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Cristaux Massifs (CrisMass), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire national des champs magnétiques intenses - Grenoble (LNCMI), Université Joseph Fourier - Grenoble 1 (UJF)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Institute of Physics of Complex Matter, Academy of Sciences of Moldova, Academy of Sciences of Moldova (ASM), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM), Institut de Chimie et Biochimie Moléculaires et Supramoléculaires (ICBMS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École Supérieure Chimie Physique Électronique de Lyon-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Scale (ratio) ,Dirac (software) ,FOS: Physical sciences ,Cadmium arsenide ,02 engineering and technology ,01 natural sciences ,chemistry.chemical_compound ,MASSLESS KANE FERMIONS ,CADMIUM ARSENIDE ,BAND-STRUCTURE ,SEMIMETAL CD3AS2 ,II3V2 COMPOUNDS ,CRYSTAL ,SEMICONDUCTORS ,PLASMON ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,010306 general physics ,Electronic band structure ,Spectroscopy ,ComputingMilieux_MISCELLANEOUS ,Plasmon ,[PHYS]Physics [physics] ,Physics ,Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics ,business.industry ,Materials Science (cond-mat.mtrl-sci) ,021001 nanoscience & nanotechnology ,Computational physics ,Semiconductor ,chemistry ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,Charge carrier ,0210 nano-technology ,business - Abstract
Cadmium arsenide (Cd3As2) has recently became conspicuous in solid-state physics due to several reports proposing that it hosts a pair of symmetry-protected 3D Dirac cones. Despite vast investigations, a solid experimental insight into the band structure of this material is still missing. Here we fill one of the existing gaps in our understanding of Cd3As2, and based on our Landau level spectroscopy study, we provide an estimate for the energy scale of 3D Dirac electrons in this system. We find that the appearance of such charge carriers is limited - contrary to a widespread belief in the solid-state community - to a relatively small energy scale (below 40 meV)., Comment: to be published in Phys. Rev. B
- Published
- 2018
4. Renormalization of Coulomb interactions in a system of two-dimensional tilted Dirac fermions
- Author
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Yu-Li Lee and Yu Wen Lee
- Subjects
Physics ,High Energy Physics::Lattice ,Observable ,Fermi surface ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Semimetal ,Renormalization ,symbols.namesake ,Dirac fermion ,Quantum electrodynamics ,Quantum mechanics ,0103 physical sciences ,Compressibility ,symbols ,Coulomb ,010306 general physics ,0210 nano-technology ,Fermi Gamma-ray Space Telescope - Abstract
We investigate the effects of long-ranged Coulomb interactions in a tilted Dirac semimetal in two dimensions by using the perturbative renormalization-group (RG) method. Depending on the magnitude of the tilting parameter, the undoped system can have either Fermi points (type I) or Fermi lines (type II). Previous studies usually performed the renormalization-group transformations by integrating out the modes with large momenta. This is problematic when the Fermi surface is open, like type-II Dirac fermions. In this work we study the effects of Coulomb interactions, following the spirit of Shankar [Rev. Mod. Phys. 66, 129 (1994)], by introducing a cutoff in the energy scale around the Fermi surface and integrating out the high-energy modes. For type-I Dirac fermions, our result is consistent with that of the previous work. On the other hand, we find that for type-II Dirac fermions, the magnitude of the tilting parameter increases monotonically with lowering energies. This implies the stability of type-II Dirac fermions in the presence of Coulomb interactions, in contrast with previous results. Furthermore, for type-II Dirac fermions, the velocities in different directions acquire different renormalization even if they have the same bare values. By taking into account the renormalization of the tilting parameter and the velocities due to the Coulomb interactions, we show that while the presence of a charged impurity leads only to charge redistribution around the impurity for type-I Dirac fermions, for type-II Dirac fermions, the impurity charge is completely screened, albeit with a very long screening length. The latter indicates that the temperature dependence of physical observables are essentially determined by the RG equations we derived. We illustrate this by calculating the temperature dependence of the compressibility and specific heat of the interacting tilted Dirac fermions.
- Published
- 2018
5. Nature of the magnetic phase transition in a Weyl semimetal
- Author
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Yu-Li Lee and Yu Wen Lee
- Subjects
Quantum phase transition ,Physics ,Gaussian fixed point ,Weyl semimetal ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Renormalization ,Critical point (thermodynamics) ,Quantum critical point ,Quantum mechanics ,0103 physical sciences ,Quasiparticle ,010306 general physics ,0210 nano-technology ,Dangerously irrelevant operator - Abstract
We investigate the nature of the magnetic phase transition induced by the short-ranged electron-electron interactions in a Weyl semimetal by using the perturbative renormalization-group method. We find that the critical point associated with the quantum phase transition is characterized by a Gaussian fixed point perturbed by a dangerously irrelevant operator. Although the low-energy and long-distance physics is governed by a free theory, the velocities of the fermionic quasiparticles and the magnetic fluctuations suffer from nontrivial renormalization effects. In particular, their ratio approaches one at low energies, which indicates an emergent Lorentz symmetry at the quantum critical point. We further investigate the stability of the fixed point in the presence of weak disorder preserving the chiral symmetry. We show that while the fixed point is generally stable against weak disorder, a moderately strong random chemical potential and/or random vector potential may induce a quantum phase transition towards a disorder-dominated phase. We propose a global phase diagram of the Weyl semimetal in the presence of both electron-electron interactions and disorder based on our results.
- Published
- 2017
6. Scale-Invariant Quantum Anomalous Hall Effect in Magnetic Topological Insulators beyond the Two-Dimensional Limit
- Author
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Ying Jiang, Wei-Li Lee, Xufeng Kou, Qiming Shao, Murong Lang, Liang He, Jianshi Tang, Shih Ting Guo, Ting-Kuo Lee, Yong Wang, Yabin Fan, Lei Pan, Kouchi Murata, Kang L. Wang, and Tianxiao Nie
- Subjects
Physics ,Condensed matter physics ,Magnetism ,Topological insulator ,Dissipative system ,General Physics and Astronomy ,Conductance ,Quantum anomalous Hall effect ,Magnetic semiconductor ,Scale invariance ,Thin film - Abstract
We investigate the quantum anomalous Hall effect (QAHE) and related chiral transport in the millimeter-size ${({\mathrm{Cr}}_{0.12}{\mathrm{Bi}}_{0.26}{\mathrm{Sb}}_{0.62})}_{2}{\mathrm{Te}}_{3}$ films. With high sample quality and robust magnetism at low temperatures, the quantized Hall conductance of ${e}^{2}/h$ is found to persist even when the film thickness is beyond the two-dimensional (2D) hybridization limit. Meanwhile, the Chern insulator-featured chiral edge conduction is manifested by the nonlocal transport measurements. In contrast to the 2D hybridized thin film, an additional weakly field-dependent longitudinal resistance is observed in the ten-quintuple-layer film, suggesting the influence of the film thickness on the dissipative edge channel in the QAHE regime. The extension of the QAHE into the three-dimensional thickness region addresses the universality of this quantum transport phenomenon and motivates the exploration of new QAHE phases with tunable Chern numbers. In addition, the observation of scale-invariant dissipationless chiral propagation on a macroscopic scale makes a major stride towards ideal low-power interconnect applications.
- Published
- 2014
7. Tunneling between a topological superconductor and a Luttinger liquid
- Author
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Yu Wen Lee and Yu-Li Lee
- Subjects
Physics ,Superconductivity ,Strongly Correlated Electrons (cond-mat.str-el) ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Quantum point contact ,FOS: Physical sciences ,Fixed point ,Edge (geometry) ,Renormalization group ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter Physics ,Topology ,Electronic, Optical and Magnetic Materials ,Condensed Matter - Strongly Correlated Electrons ,MAJORANA ,Luttinger liquid ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Quantum tunnelling - Abstract
We study the quantum point contact between the topological superconductor and the helical Luttinger liquid. The effects of the electron-electron interactions in the helical Luttinger liquid on the low-energy physics of this system are analyzed by the renormalization group. Among the various couplings at the point contact which arise from the tunneling via the Majorana edge channel, the induced backscattering in the helical Luttinger liquid is the most relevant for repulsive interactions. Hence, at low temperatures, the helical Luttinger liquid is effectively cut into two separated half wires. As a result, the low-temperature physics is described by a fixed point consisting of two leads coupled to the topological superconductor, and the electrical transport properties through the point contact at low temperature and low bias are dominated by the tunneling via the Majorana edge channel. We compute the temperature dependence of the zero-bias tunneling conductance and study the full counting statistics for the tunneling current at zero temperature., 7 pages, 2 figure
- Published
- 2014
8. Low-energy effective action of lightly doped two-legt−Jladders
- Author
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Yu-Wen Lee and Yu-Li Lee
- Subjects
Physics ,Strongly Correlated Electrons (cond-mat.str-el) ,Sigma model ,Condensed matter physics ,FOS: Physical sciences ,Fermion ,Renormalization group ,Condensed Matter - Strongly Correlated Electrons ,symbols.namesake ,Dirac fermion ,Quantum mechanics ,symbols ,Effective field theory ,Condensed Matter::Strongly Correlated Electrons ,Hamiltonian (quantum mechanics) ,Charge density wave ,Boson - Abstract
We propose a low energy effective theory of lightly doped two-leg t-J ladders with the help of slave fermion technique. The continuum limit of this model consists of two kinds of Dirac fermions which are coupled to the O(3) non-linear sigma model in terms of the gauge coupling with opposite sign of "charges". In addition to the gauge interaction, there is another kind of attractive force between these Dirac fermions, which arises from the short-ranged antiferromagnetic order. We show that the latter is essential to determine the low energy properties of lightly doped two-leg t-J ladders. The effective Hamiltonian we obtain is a bosonic Gaussian model and the boson field basically describes the particle density fluctuation. We also find two types of gapped spin excitations. Finally, we discuss the possible instabilities: charge density wave (CDW) and singlet superconductivity (SC). We find that the SC instability dominates in our approximation. Our results indicate that lightly doped ladders fall into the universality class of Luther-Emery model., Comment: 16 pages, Revtex, no figures
- Published
- 1999
9. Spontaneous parity breaking in three-dimensional non-Abelian gauge theory
- Author
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Y. Kao, Hsien Chung Kao, and Yu Li Lee
- Subjects
Physics ,High Energy Physics::Theory ,Nuclear and High Energy Physics ,Gauge boson ,Higgs field ,Theoretical physics ,Quantum mechanics ,Higgs boson ,Parity (physics) ,Vacuum polarization ,Gauge theory ,Symmetry breaking ,Effective action - Abstract
We study the parity-odd part of the gauge field two-point function in the effective action in three-dimensional non-Abelian gauge theory with both Higgs fields and the Chern-Simons term. It is shown that, contrary to a previous proposal, there is no hint of spontaneous parity breakdown up to one-loop level, if care is taken to turn off the Chern-Simons coefficient before expanding the effective action into local terms. {copyright}{ital 1996 The American Physical Society.}
- Published
- 1996
10. Nonstoichiometric doping and Bi antisite defect in single crystal Bi2Se3
- Author
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Sz-Chian Liou, Hsiang-Hsi Kung, Y. K. Kuo, Fangcheng Chou, Ming-Wen Chu, Wei-Li Lee, Fei-Ting Huang, Raman Sankar, and Kai-Hsin Wu
- Subjects
Diffraction ,Materials science ,Condensed matter physics ,Hall effect ,Intercalation (chemistry) ,Scanning transmission electron microscopy ,Doping ,Condensed Matter Physics ,Spectroscopy ,Single crystal ,Stoichiometry ,Electronic, Optical and Magnetic Materials - Abstract
We studied the defects of Bi2Se3 generated from Bridgman growth of stoichiometric and nonstoichiometric self-fluxes. Growth habit, lattice size, and transport properties are strongly affected by the types of defects generated. Major defect types of the BiSe antisite and partial Bi2-layer intercalation are identified through combined studies of direct atomic-scale imaging with scanning transmission electron microscopy in conjunction with energy-dispersive x-ray spectroscopy, x-ray diffraction, and Hall effect measurements. We propose a consistent explanation to the origin of defect type, growth morphology, and transport property.
- Published
- 2012
11. Electronic phase diagram of LixCoO2revisited with potentiostatically deintercalated single crystals
- Author
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G. J. Shu, T. Y. Ou-Yang, M.-W. Chu, Fei-Ting Huang, Hsiang Lin Liu, Wei-Li Lee, and F. C. Chou
- Subjects
Magnetic anisotropy ,Materials science ,Condensed matter physics ,Phase (matter) ,Vacancy defect ,X-ray crystallography ,Antiferromagnetism ,Condensed Matter Physics ,Single crystal ,Magnetic susceptibility ,Electronic, Optical and Magnetic Materials ,Phase diagram - Abstract
Electronic phase diagram of LixCoO2 has been re-examined using potentiostatically de-intercalated single crystal samples. Stable phases of x ~ 0.87, 0.72, 0.53, 0.50, 0.43, and 0.33 were found and isolated for physical property studies. A-type and chain-type antiferromagnetic orderings have been suggested from magnetic susceptibility measurement results in x ~ 0.87 and 0.50 below ~ 10 K and 200 K, respectively, similar to those found in NaxCoO2 system. There is no Li vacancy superlattice ordering observed at room temperature for the electronically stable phase Li0.72CoO2 as revealed by synchrotron X-ray Laue diffraction. The peculiar magnetic anomaly near ~ 175 K as often found in powder samples of x ~ 0.46-0.78 cannot be isolated through this single crystal potentiostatic method, which supports the previously proposed explanation to be surface stabilized phase of significant thermal hysteresis and aging character.
- Published
- 2012
12. Enhanced Thermoelectric Power in Dual-Gated Bilayer Graphene
- Author
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Lei Hao, Wei-Li Lee, Jian-Zhang Chen, Ting-Kuo Lee, Wen-Sen Lu, Feng Lin, I-Chun Cheng, and C. W. Wang
- Subjects
Condensed Matter - Materials Science ,Materials science ,Thermoelectric cooling ,Condensed Matter - Mesoscale and Nanoscale Physics ,Band gap ,business.industry ,Graphene ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,General Physics and Astronomy ,Thermoelectric materials ,law.invention ,Thermoelectric generator ,law ,Seebeck coefficient ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Thermoelectric effect ,Optoelectronics ,Bilayer graphene ,business - Abstract
Thermoelectric power of a material, typically governed by its band structure and carrier density, can be varied by chemical doping that is often restricted by solubility of the dopant. Materials showing large thermoelectric power are useful for many industrial applications, such as the heat-to-electricity conversion and the thermoelectric cooling device. Here we show a full electric field tuning of thermoelectric power in a dual-gated bilayer graphene device resulting from the opening of a band-gap by applying a perpendicular electric field on bilayer graphene. We uncover a large enhancement in thermoelectric power at low temperature, which may open up a new possibility in low temperature thermoelectric application using graphene-based device., 12 pages, 4 figures
- Published
- 2011
13. Superconducting to spin-glass state transformation inβ-pyrochloreKxOs2O6
- Author
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C. C. Tsuei, C. C. Lee, J. G. Lin, Wei-Li Lee, Jiunn-Yuan Lin, and F. C. Chou
- Subjects
Superconductivity ,Materials science ,Spin glass ,Condensed matter physics ,Pyrochlore ,Charge (physics) ,State (functional analysis) ,engineering.material ,Condensed Matter Physics ,Electrochemistry ,Magnetic susceptibility ,Electronic, Optical and Magnetic Materials ,Electrical resistivity and conductivity ,engineering - Abstract
$\ensuremath{\beta}$-pyrochore KOs${}_{2}$O${}_{6}$, which shows superconductivity below $~9.7$ K, has been converted into ${\mathrm{K}}_{x}$Os${}_{2}$O${}_{6}$ ($x\ensuremath{\lesssim}\frac{2}{3}$--$\frac{1}{2}$) electrochemically to show spin-glass-like behavior below $~6.1$ K. A room-temperature sample surface potential versus charge transfer scan indicates that there are at least two two-phase regions for $x$ between 1 and 0.5. A rattling model of superconductivity for the title compound has been examined using electrochemical potassium de-intercalation. The significant reduction of superconducting volume fraction due to minor potassium reduction suggests the importance of defect and phase coherence in the rattling model. Magnetic susceptibility, resistivity, and specific heat measurement results have been compared between the superconducting and spin-glass-like samples.
- Published
- 2011
14. Nonmagnetic impurity perturbation to the quasi-two-dimensional quantum helimagnetLiCu2O2
- Author
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Ying-Jer Kao, C. D. Hu, Takashi Imai, Ming-Wen Chu, Wei-Li Lee, Fangcheng Chou, Jiunn-Yuan Lin, Hsu Cheng Hsu, and Hsiang Lin Liu
- Subjects
Physics ,Condensed matter physics ,Spins ,Transition temperature ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Inductive coupling ,Electronic, Optical and Magnetic Materials ,Polarization density ,0103 physical sciences ,Multiferroics ,Quadratic field ,010306 general physics ,0210 nano-technology ,Series expansion ,Phase diagram - Abstract
A complete phase diagram of Zn-substituted quantum quasi-two-dimensional helimagnet ${\text{LiCu}}_{2}{\text{O}}_{2}$ has been presented. Helical ordering transition temperature $({T}_{h})$ of the original ${\text{LiCu}}_{2}{\text{O}}_{2}$ follows finite size scaling for less than $\ensuremath{\sim}5.5\mathrm{%}$ Zn substitution, which implies the existence of finite helimagnetic domains with domain boundaries formed with nearly isolated spins. Higher Zn substitution $\ensuremath{\ge}5.5\mathrm{%}$ quenches the long-range helical ordering and introduces an intriguing Zn-level-dependent magnetic phase transition with slight thermal hysteresis and a universal quadratic field dependence for ${T}_{c}(\text{Zn}g0.055,\text{H})$. The magnetic coupling constants of nearest-neighbor ${J}_{1}$ and next-nearest-neighbor ${J}_{2}$ $(\ensuremath{\alpha}={J}_{2}/{J}_{1})$ are extracted from high temperature series expansion fitting and $N=16$ finite chain exact diagonalization simulation. We have also provided evidence of direct correlation between long-range helical spin ordering and the magnitude of electric polarization in this spin-driven multiferroic material.
- Published
- 2010
15. Oxygen nonstoichiometry and the origin of Na ion ordering inP2-NaxCoO2
- Author
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Fei-Ting Huang, Fangcheng Chou, G. J. Shu, Ming-Wen Chu, Wei-Li Lee, and Patrick A. Lee
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Physics ,Valence (chemistry) ,Condensed matter physics ,Hexagonal crystal system ,Superlattice ,chemistry.chemical_element ,Oxygen deficiency ,Condensed Matter Physics ,Magnetic susceptibility ,Oxygen ,Electronic, Optical and Magnetic Materials ,Crystallography ,chemistry ,X-ray crystallography - Abstract
The impact of oxygen deficiency on physical properties of ${\text{Na}}_{2/3}{\text{CoO}}_{2\ensuremath{-}\ensuremath{\delta}}$ has been investigated. From the combined thermogravimetric, magnetic susceptibility, and synchrotron x-ray Laue diffraction studies, it is demonstrated that ${\text{Na}}_{2/3}{\text{CoO}}_{2}$ shows no superlattice ordering due to Na ions; however ${\text{Na}}_{2/3}{\text{CoO}}_{1.98}$, which has the same Co valence as that of ${\text{Na}}_{0.71}{\text{CoO}}_{2}$, shows nearly identical magnetic and transport properties and the same simple hexagonal superlattice ordering of $\sqrt{12}a$. It is proposed that the Na ion ordering found in ${\text{Na}}_{2/3}{\text{CoO}}_{1.98}$ is identical to the ideal ${\text{Na}}_{0.71}{\text{CoO}}_{2}$ of large $\sqrt{12}a\ifmmode\times\else\texttimes\fi{}\sqrt{12}a\ifmmode\times\else\texttimes\fi{}3c$ superlattice but with additional Na vacancies which are bound to the oxygen defects at room temperature. We conclude that oxygen vacancies play a key role in stabilizing the superlattice structure and must be accounted for in its modeling.
- Published
- 2010
16. Sodium ion ordering ofNa0.77CoO2under competing multivacancy cluster, superlattice, and domain formation
- Author
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G. J. Shu, Fangcheng Chou, Hwo-Shuenn Sheu, Wei-Li Lee, M.-W. Chu, Y. K. Kuo, and F.-T. Huang
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Range (particle radiation) ,Materials science ,Condensed matter physics ,Spinodal decomposition ,Sodium ,Superlattice ,chemistry.chemical_element ,Temperature cycling ,Condensed Matter Physics ,Magnetic hysteresis ,Synchrotron ,Electronic, Optical and Magnetic Materials ,law.invention ,Condensed Matter::Materials Science ,chemistry ,law ,Cluster (physics) - Abstract
Hexagonal superlattice formed by sodium multivacancy-cluster ordering in Na0.77CoO2 has been proposed based on synchrotron x-ray Laue-diffraction study on electrochemically fine-tuned single crystals. The title compound sits closely to the proposed lower end of the miscibility gap of x0.77‐0.82 phase-separated range. The average sodium vacancy-cluster size is estimated to be 4.5 Na vacancies per layer within a large superlattice size of 19a19a3c. The exceptionally large Na vacancy-cluster size favors large twinned simple hexagonal superlattice of 19a, in competition with the smaller divacancy, trivacancy, and quadrivacancy clusters formed superlattices of 12a and 13a. Competing electronic correlations are revealed by the observed spin-glasslike magnetic hysteresis below 3 K and the twin domain, triple domain, and monodomain transformations during thermal cycling between 273 and 373 K.
- Published
- 2009
17. Low-energy properties of the ferromagnetic metallic phase in manganites: Slave-fermion approach to the quantum double-exchange model
- Author
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Yu-Wen Lee and Yu-Li Lee
- Subjects
Physics ,Condensed matter physics ,Ferromagnetism ,Phase (matter) ,Density of states ,Quasiparticle ,Condensed Matter::Strongly Correlated Electrons ,Fermion ,Electron ,Condensed Matter Physics ,Quantum ,Quantum tunnelling ,Electronic, Optical and Magnetic Materials - Abstract
We study the low-energy properties of the one-orbital quantum double-exchange model by using the slave fermion formulation. We construct a mean-field theory which gives a simple explanation for the magnetic and thermodynamic properties of the ferromagnetic metallic phase in manganites at low energy. The resulting electron spectral function and tunneling density of states show an incoherent asymmetric peak with weak temperature dependence, in addition to a quasiparticle peak. We also show that the gauge fluctuations in the ferromagnetic metallic phase are completely screened due to the Anderson-Higgs mechanism. Therefore, the mean-field state is robust against gauge fluctuations and exhibits spin-charge separation at low energy.
- Published
- 2007
18. Quantum phases of a Feshbach-resonant atomic Bose gas in one dimension
- Author
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Yu-Li Lee and Yu-Wen Lee
- Subjects
Condensed Matter::Quantum Gases ,Physics ,Statistical Mechanics (cond-mat.stat-mech) ,Bose gas ,Condensed matter physics ,Condensed Matter - Superconductivity ,Atoms in molecules ,FOS: Physical sciences ,Charge density ,Quantum phases ,Atomic and Molecular Physics, and Optics ,law.invention ,Superconductivity (cond-mat.supr-con) ,Luttinger liquid ,law ,Physics::Atomic and Molecular Clusters ,Physics::Atomic Physics ,Feshbach resonance ,Charge density wave ,Condensed Matter - Statistical Mechanics ,Bose–Einstein condensate - Abstract
We study an atomic Bose gas with an s-wave Feshbach resonance in a one-dimensional optical lattice, with the densities of atoms and molecules incommensurate with the lattice. At zero temperature, most of the parameter region is occupied by a phase in which the superfluid fluctuations of atoms and molecules are the predominant ones, due to the phase fluctuations of atoms and molecules being locked by a Josephson coupling between them. When the density difference between atoms and molecules is commensurate with the lattice, two additional phases may exist: the two component Luttinger liquid where both the atomic and molecular sectors are gapless, and the inter-channel charge density wave where the relative density fluctuations between atoms and molecules are frozen at low energy., Comment: 4+epsilon pages, 3 figures; references added
- Published
- 2006
19. Quantum phase transition in an atomic Bose gas near a Feshbach resonance
- Author
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Yu Wen Lee and Yu-Li Lee
- Subjects
Condensed Matter::Quantum Gases ,Quantum phase transition ,Physics ,Phase transition ,Statistical Mechanics (cond-mat.stat-mech) ,Condensed matter physics ,Bose gas ,Condensed Matter - Superconductivity ,FOS: Physical sciences ,Quantum phases ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,law.invention ,Superconductivity (cond-mat.supr-con) ,law ,Quantum mechanics ,Quantum critical point ,Ising model ,Feshbach resonance ,Condensed Matter - Statistical Mechanics ,Bose–Einstein condensate - Abstract
We study the quantum phase transition in an atomic Bose gas near a Feshbach resonance in terms of the renormalization group. This quantum phase transition is characterized by an Ising order parameter. We show that in the low temperature regime where the quantum fluctuations dominate the low-energy physics this phase transition is of first order because of the coupling between the Ising order parameter and the Goldstone mode existing in the bosonic superfluid. However, when the thermal fluctuations become important, the phase transition turns into the second order one, which belongs to the three-dimensional Ising universality class. We also calculate the damping rate of the collective mode in the phase with only a molecular Bose-Einstein condensate near the second-order transition line, which can serve as an experimental signature of the second-order transition., 8 pages, 2 figures, published version in Phys. Rev. B
- Published
- 2004
20. Anomalous Hall Heat Current and Nernst Effect in theCuCr2Se4−xBrxFerromagnet
- Author
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Wei-Li Lee, Nai Phuan Ong, V.L. Miller, Robert J. Cava, and Satoshi Watauchi
- Subjects
Physics ,Heat current ,Condensed matter physics ,General Physics and Astronomy ,02 engineering and technology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,01 natural sciences ,symbols.namesake ,Ferromagnetism ,Seebeck coefficient ,0103 physical sciences ,symbols ,010306 general physics ,0210 nano-technology ,Nernst effect - Abstract
In a ferromagnet, an anomalous Hall heat current, given by the off-diagonal Peltier term ${\ensuremath{\alpha}}_{xy}$, accompanies the anomalous Hall current. By combining Nernst, thermopower, and Hall experiments, we have measured how ${\ensuremath{\alpha}}_{xy}$ varies with hole density and lifetime $\ensuremath{\tau}$ in ${\mathrm{C}\mathrm{u}\mathrm{C}\mathrm{r}}_{2}{\mathrm{S}\mathrm{e}}_{4\ensuremath{-}x}{\mathrm{B}\mathrm{r}}_{x}$. At low temperatures $T$, we find that ${\ensuremath{\alpha}}_{xy}$ is independent of $\ensuremath{\tau}$, consistent with anomalous-velocity theories. Its magnitude is fixed by a microscopic geometric area $\mathcal{A}\ensuremath{\sim}34\text{ }\text{ }{\AA{}}^{2}$. Our results are incompatible with some models of the Nernst effect in ferromagnets.
- Published
- 2004
21. Quantum dynamics of tunneling between ferromagnets
- Author
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Yu-Li Lee and Yu-Wen Lee
- Subjects
Josephson effect ,Physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Spin polarization ,Condensed Matter - Superconductivity ,Spin valve ,FOS: Physical sciences ,law.invention ,Superconductivity (cond-mat.supr-con) ,Pi Josephson junction ,SQUID ,Magnetization ,law ,Condensed Matter::Superconductivity ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Spinplasmonics ,Spin Hall effect ,Condensed Matter::Strongly Correlated Electrons - Abstract
We study the Josephson-like spin currents between two ferromagnetic metals by deriving the effective action of the junction. A DC spin Josephson current with the full O(3) symmetry is obtained. By the analogy to the superconducting junctions, we have shown that a time-independent uniform magnetic field can serve as the source of the AC spin Josephson effect. That is, the spin current becomes a periodic function of the time with the period proportional to the inverse of the magnitude of the external magnetic field., Phys. Rev. B 68, 184413 (2003)
- Published
- 2003
22. Screening mass in the massive Schwinger model at infinite temperature
- Author
-
Y. Kao and Yu Li Lee
- Subjects
Physics ,Nuclear and High Energy Physics ,Thermal quantum field theory ,High Energy Physics::Lattice ,Quantum electrodynamics ,High Energy Physics::Phenomenology ,Order (ring theory) ,Higgs phase - Abstract
The massive Schwinger model is in the Higgs phase only at infinite temperature. We calculate its screening mass to one-loop order and make comparisons with related studies.
- Published
- 1998
23. Erratum: Three-dimensional multispecies nonlinear perturbative particle simulations of collective processes in intense particle beams [Phys. Rev. ST Accel. Beams 3, 084401 (2000)]
- Author
-
Qin, Hong, primary, Davidson, Ronald C., additional, and Wei-li Lee, W., additional
- Published
- 2000
- Full Text
- View/download PDF
24. Three-dimensional multispecies nonlinear perturbative particle simulations of collective processes in intense particle beams
- Author
-
Qin, Hong, primary, Davidson, Ronald C., additional, and Wei-li Lee, W., additional
- Published
- 2000
- Full Text
- View/download PDF
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