19 results on '"Michael M. Fogler"'
Search Results
2. Sum-Rule Constraints on the Surface State Conductance of Topological Insulators
- Author
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Nitin Samarth, Joon Sue Lee, Kirk Post, A. Richardella, Jhih-Sheng Wu, B. C. Chapler, H. T. Stinson, Anjan Reijnders, Michael Goldflam, Michael M. Fogler, Mengkun Liu, Kenneth S. Burch, and Dimitri Basov
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Physics ,Condensed Matter::Materials Science ,Magnetoresistance ,Condensed matter physics ,Band gap ,Oscillator strength ,Topological insulator ,General Physics and Astronomy ,Charge carrier ,Sum rule in quantum mechanics ,Upper and lower bounds ,Surface states - Abstract
We report the Drude oscillator strength D and the magnitude of the bulk band gap E_{g} of the epitaxially grown, topological insulator (Bi,Sb)_{2}Te_{3}. The magnitude of E_{g}, in conjunction with the model independent f-sum rule, allows us to establish an upper bound for the magnitude of D expected in a typical Dirac-like system composed of linear bands. The experimentally observed D is found to be at or below this theoretical upper bound, demonstrating the effectiveness of alloying in eliminating bulk charge carriers. Moreover, direct comparison of the measured D to magnetoresistance measurements of the same sample supports assignment of the observed low-energy conduction to topological surface states.
- Published
- 2015
3. Electronic response of graphene to linelike charge perturbations
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Michael M. Fogler and Bor-Yuan Jiang
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Physics ,Electron density ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Condensed Matter::Other ,Graphene ,Fluids & Plasmas ,Doping ,Physics::Optics ,FOS: Physical sciences ,Conductance ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,law.invention ,Quantum capacitance ,Engineering ,law ,Condensed Matter::Superconductivity ,cond-mat.mes-hall ,Physical Sciences ,Chemical Sciences ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Charge carrier ,Bilayer graphene ,Graphene nanoribbons - Abstract
The problem of electrostatic screening of a charged line by undoped or weakly doped graphene is treated beyond the linear-response theory. The induced electron density is found to be approximately doping independent, n(x)~(log x)^2/x^2, at intermediate distances x from the charged line. At larger x, twin p-n junctions may form if the external perturbation is repulsive for graphene charge carriers. The effect of such inhomogeneities on conductance and quantum capacitance of graphene is calculated. The results are relevant for transport properties of graphene grain boundaries and for local electrostatic control of graphene with ultrathin gates., Comment: Fixed typos and added references
- Published
- 2015
4. Dynamical response of a pinned two-dimensional Wigner crystal
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David A. Huse and Michael M. Fogler
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Physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Phonon ,FOS: Physical sciences ,Disordered Systems and Neural Networks (cond-mat.dis-nn) ,02 engineering and technology ,Condensed Matter - Disordered Systems and Neural Networks ,Quantum Hall effect ,021001 nanoscience & nanotechnology ,01 natural sciences ,Resonance (particle physics) ,Wigner crystal ,Magnetic field ,Laser linewidth ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,cond-mat.mes-hall ,0103 physical sciences ,Quasiparticle ,Density of states ,cond-mat.dis-nn ,010306 general physics ,0210 nano-technology - Abstract
We re-examine a long-standing problem of a finite-frequency conductivity of a weakly pinned two-dimensional classical Wigner crystal. In this system an inhomogeneously broadened absorption line (pinning mode) centered at disorder and magnetic field dependent frequency $\omega_p$ is known to appear. We show that the relative linewidth $\Delta \omega_p / \omega_p$ of the pinning mode is of the order of one in weak magnetic fields, exhibits a power-law decrease in intermediate fields, and eventually saturates at a small value in strong magnetic fields. The linewidth narrowing is due to a peculiar mechanism of mixing between the stiffer longitudinal and the softer transverse components of the collective excitations. The width of the high-field resonance proves to be related to the density of states in the low-frequency tail of the zero-field phonon spectrum. We find a qualitative agreement with recent experiments and point out differences from the previous theoretical work on the subject., Comment: 19 pages, 11 figures. Supersedes cond-mat/9904245
- Published
- 2000
5. Cyclotron Resonance in a Two-Dimensional Electron Gas with Long-Range Randomness
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Boris I Shklovskii and Michael M. Fogler
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Physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Cyclotron resonance ,FOS: Physical sciences ,General Physics and Astronomy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electron cyclotron resonance ,Magnetic field ,Laser linewidth ,Wavelength ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Atomic physics ,010306 general physics ,0210 nano-technology ,Fermi gas ,Motional narrowing ,Ion cyclotron resonance - Abstract
We show that the the cyclotron resonance in a two-dimensional electron gas has non-trivial properties if the correlation length of the disorder is larger than the de Broglie wavelength: (a) the lineshape assumes three different forms in strong, intermediate, and weak magnetic fields (b) at the transition from the intermediate to the weak fields the linewidth suddenly collapses due to an explosive growth in the fraction of electrons with a diffusive-type dynamics., Comment: A few typos corrected
- Published
- 1998
6. Suppression of chaotic dynamics and localization of two-dimensional electrons by a weak magnetic field
- Author
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Boris I Shklovskii, V. I. Perel, A. Yu. Dobin, and Michael M. Fogler
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Physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Field (physics) ,Condensed matter physics ,FOS: Physical sciences ,Equations of motion ,02 engineering and technology ,Electron ,Quantum Hall effect ,Nonlinear Sciences - Chaotic Dynamics ,021001 nanoscience & nanotechnology ,01 natural sciences ,Charged particle ,Magnetic field ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Matter wave ,Chaotic Dynamics (nlin.CD) ,Diffusion (business) ,010306 general physics ,0210 nano-technology - Abstract
We study a two-dimensional motion of a charged particle in a weak random potential and a perpendicular magnetic field. The correlation length of the potential is assumed to be much larger than the de Broglie wavelength. Under such conditions, the motion on not too large length scales is described by classical equations of motion. We show that the phase-space averaged diffusion coefficient is given by Drude-Lorentz formula only at magnetic fields $B$ smaller than certain value $B_c$. At larger fields, the chaotic motion is suppressed and the diffusion coefficient becomes exponentially small. In addition, we calculate the quantum-mechanical localization length as a function of $B$ in the minima of $��_{xx}$. At $B < B_c$ it is exponentially large but decreases with increasing $B$. At $B > B_c$, the localization length drops precipitously, and ceases to be exponentially large at a field $B_\ast$, which is only slightly above $B_c$. Implications for the crossover from the Shubnikov-de Haas oscillations to the quantum Hall effect are discussed., 20 pages, 5 figures
- Published
- 1997
7. Laughlin liquid to charge-density-wave transition at high Landau levels
- Author
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Michael M. Fogler and Alexei A. Koulakov
- Subjects
Physics ,Laughlin wavefunction ,Condensed matter physics ,Landau quantization ,Quantum Hall effect ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Charge density wave ,Energy (signal processing) ,Magnetic field - Abstract
We compare the energies of the Laughlin liquid and a charge density wave in a weak magnetic field for the upper Landau-level filling factors ${\ensuremath{\nu}}_{\mathrm{N}}$= and . The charge-density-wave period has been optimized and was found to be \ensuremath{\simeq}3.${3\mathrm{R}}_{\mathrm{c}}$, where ${\mathrm{R}}_{\mathrm{c}}$ is the cyclotron radius. We conclude that the optimal charge density wave is lower in energy than the Laughlin liquid for the Landau-level numbers N\ensuremath{\geqslant}2 at ${\ensuremath{\nu}}_{\mathrm{N}}$= and for N\ensuremath{\geqslant}3 at ${\ensuremath{\nu}}_{\mathrm{N}}$=. This implies that the quantum Hall plateaus cannot be observed for N\ensuremath{\geqslant}2, in agreement with the experiment.
- Published
- 1997
8. Chemical potential and magnetization of a Coulomb island
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Boris I Shklovskii, Michael M. Fogler, and E. I. Levin
- Subjects
Physics ,Electron density ,Magnetization ,Condensed matter physics ,Quantum wire ,Magnetic pressure ,Magnetic potential ,Electron ,Bohr radius ,Magnetic field - Abstract
We consider variations of the low temperature chemical potential and magnetization of laterally confined two-dimensional interacting electrons in a strong magnetic field. Cases of axially symmetrical (a quantum dot) and strongly elongated (a quantum wire) spatial distributions of electron density are studied. We commonly refer to both types of systems as ``islands.'' The calculations are performed in the mean-field approximation. In this approximation the system consists of alternating regions of compressible and incompressible liquids. We are focusing on islands with typical widths b, which are much larger than the Bohr radius in a semiconductor ${\mathit{a}}_{\mathit{B}}$, and argue that the density profile is formed mainly by electrostatic forces, has a domelike shape, and changes only slightly in the whole range of magnetic fields. We calculated numerically the chemical potential and the magnetization as functions of the magnetic field and found them to be in sharp contrast to the conventional result for noninteracting electrons. We suggest a simple analytic theory adequately explaining these functional dependences. The results are compared with the experimental data.
- Published
- 1994
9. Model of large volumetric capacitance in graphene supercapacitors based on ion clustering
- Author
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Brian Skinner, Boris I Shklovskii, and Michael M. Fogler
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Materials science ,FOS: Physical sciences ,Nanotechnology ,02 engineering and technology ,Electron ,01 natural sciences ,7. Clean energy ,Molecular physics ,law.invention ,Ion ,Stack (abstract data type) ,law ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Absorption (logic) ,010306 general physics ,Supercapacitor ,Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Graphene ,Materials Science (cond-mat.mtrl-sci) ,Charge (physics) ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,3. Good health ,Electronic, Optical and Magnetic Materials ,Electrode ,0210 nano-technology - Abstract
Electric double layer supercapacitors are promising devices for high-power energy storage based on the reversible absorption of ions into porous, conducting electrodes. Graphene is a particularly good candidate for the electrode material in supercapacitors due to its high conductivity and large surface area. In this paper we consider supercapacitor electrodes made from a stack of graphene sheets with randomly-inserted "spacer" molecules. We show that the large volumetric capacitances C > 100 F/cm^3 observed experimentally can be understood as a result of collective intercalation of ions into the graphene stack and the accompanying nonlinear screening by graphene electrons that renormalizes the charge of the ion clusters., 13 pages, 5 figures; additional discussion and supporting calculations added
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- 2011
10. Hopping transport in systems of finite thickness or length
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Michael M. Fogler and Aleksandr Rodin
- Subjects
Physics ,Resistive touchscreen ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,FOS: Physical sciences ,Disordered Systems and Neural Networks (cond-mat.dis-nn) ,Condensed Matter - Disordered Systems and Neural Networks ,Condensed Matter Physics ,Variable-range hopping ,Electronic, Optical and Magnetic Materials ,law.invention ,Percolation theory ,Dimension (vector space) ,law ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Resistor ,Finite thickness ,Curse of dimensionality - Abstract
Variable-range hopping transport along short one-dimensional wires and across the shortest dimension of thin three-dimensional films and narrow two-dimensional ribbons is studied theoretically. Geometric and transport characteristics of the hopping resistor network are shown to depend on temperature T and the dimensionality of the system. In two and three dimensions the usual Mott law applies at high T where the correlation length of the network is smaller than the sample thickness. As T decreases, the network breaks into sparse filamentary paths, while the Mott law changes to a different T-dependence, which is derived using the percolation theory methods. In one dimension, deviations from the Mott law are known to exist at all temperatures because of rare fluctuations. The evolution of such fluctuations from highly-resistive "breaks" at high T to highly-conducting "shorts" at low T is elucidated., Comment: 10 pages, 8 figures
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- 2011
11. Microwaving and stirring the quantum Hall spaghetti
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Michael M. Fogler
- Subjects
Physics ,Condensed matter physics ,Quantum mechanics ,Quantum Hall effect - Published
- 2011
12. Comment on 'Screening in gated bilayer graphene'
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Michael M. Fogler and Edward McCann
- Subjects
Physics ,Condensed matter physics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Transverse plane ,Variational method ,Quantum mechanics ,Electric field ,0103 physical sciences ,010306 general physics ,0210 nano-technology ,Bilayer graphene - Abstract
We analyze the response of bilayer graphene to an external transverse electric field using a variational method. A previous attempt to do so in a recent paper by Falkovsky [Phys. Rev. B 80, 113413 (2009)] is shown to be flawed. Our calculation reaffirms the original results obtained by one of us [E. McCann, Phys. Rev. B 74, 161403(R) (2006)] by a different method. Finally, we generalize these original results to describe a dual-gated bilayer graphene device.
- Published
- 2010
13. Neutrality Point of Graphene with Coplanar Charged Impurities
- Author
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Michael M. Fogler
- Subjects
FOS: Physical sciences ,General Physics and Astronomy ,02 engineering and technology ,Electron ,Dielectric ,Conductivity ,7. Clean energy ,01 natural sciences ,law.invention ,law ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,Coulomb ,010306 general physics ,Physics ,Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Graphene ,Materials Science (cond-mat.mtrl-sci) ,Charge (physics) ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Atomic physics ,0210 nano-technology ,Ground state ,Dimensionless quantity - Abstract
The ground-state and the transport properties of graphene subject to the potential of in-plane charged impurities are studied. The screening of the impurity potential is shown to be nonlinear, producing a fractal structure of electron and hole puddles. Statistical properties of this density distribution as well as the charge compressibility of the system are calculated in the leading-log approximation. The conductivity depends logarithmically on $\alpha$, the dimensionless strength of the Coulomb interaction. The theory is asymptotically exact when $\alpha$ is small, which is the case for graphene on a substrate with a high dielectric constant., Comment: (v3) 4 pages main paper, 2 pages supplementary info, no figures
- Published
- 2009
14. Publisher's Note: Numerical studies of variable-range hopping in one-dimensional systems [Phys. Rev. B80, 155435 (2009)]
- Author
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Michael M. Fogler and Aleksandr Rodin
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Physics ,Quantum mechanics ,Condensed Matter Physics ,Variable-range hopping ,Electronic, Optical and Magnetic Materials - Published
- 2009
15. Trapping Indirect Excitons in a GaAs Quantum-Well Structure with a Diamond-Shaped Electrostatic Trap
- Author
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Alexander High, Andrew Meyertholen, Gabriele Grosso, Aaron Hammack, Arthur C. Gossard, Mikas Remeika, Micah Hanson, Leonid Butov, Michael M. Fogler, and A. K. Thomas
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Condensed Matter::Quantum Gases ,Materials science ,Condensed Matter::Other ,Exciton ,General Physics and Astronomy ,Diamond ,Trapping ,engineering.material ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Trap (computing) ,Condensed Matter::Materials Science ,Magnetic trap ,engineering ,Physics::Atomic Physics ,Atomic physics ,Biexciton ,Quantum well ,Evaporative cooler - Abstract
We report on the principle and realization of a new trap for excitons---the diamond electrostatic trap---which uses a single electrode to create a confining potential for excitons. We also create elevated diamond traps which permit evaporative cooling of the exciton gas. We observe the collection of excitons towards the trap center with increasing exciton density. This effect is due to screening of disorder in the trap by the excitons. As a result, the diamond trap behaves as a smooth parabolic potential which realizes a cold and dense exciton gas at the trap center.
- Published
- 2009
16. Effect of spatial resolution on the estimates of the coherence length of excitons in quantum wells
- Author
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Aaron Hammack, Michael M. Fogler, Sen Yang, Leonid Butov, and Arthur C. Gossard
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Condensed Matter::Quantum Gases ,Physics ,Diffraction ,Coherence time ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed Matter::Other ,Exciton ,FOS: Physical sciences ,02 engineering and technology ,Degree of coherence ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Coherence length ,Interferometry ,Quantum mechanics ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,010306 general physics ,0210 nano-technology ,Quantum well ,Coherence (physics) - Abstract
We evaluate the effect of diffraction-limited resolution of the optical system on the estimates of the coherence length of 2D excitons deduced from the interferometric study of the exciton emission. The results are applied for refining our earlier estimates of the coherence length of a cold gas of indirect excitons in coupled quantum wells [S. Yang et al., Phys. Rev. Lett. 97, 187402(2006)]. We show that the apparent coherence length is well approximated by the quadratic sum of the actual exciton coherence length and the diffraction correction given by the conventional Abbe limit divided by 3.14. In practice, accounting for diffraction is necessary only when the coherence length is smaller than about one wavelength. The earlier conclusions regarding the strong enhancement of the exciton coherence length at low temperatures remain intact., Comment: 6 pages, 5 figures
- Published
- 2008
17. Erratum: Electrostatics of two-dimensional structures: Exact solutions and approximate methods [Phys. Rev. B69, 245321 (2004)]
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Michael M. Fogler
- Subjects
Physics ,Single electron tunneling ,Quantum mechanics ,Coulomb blockade ,Condensed Matter Physics ,Electrostatics ,Electronic, Optical and Magnetic Materials - Published
- 2004
18. Nonlinear screening and percolative transition in a two-dimensional electron liquid
- Author
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Michael M. Fogler
- Subjects
Physics ,Percolation critical exponents ,Condensed Matter - Mesoscale and Nanoscale Physics ,Condensed matter physics ,Electron liquid ,FOS: Physical sciences ,Inverse ,Percolation threshold ,Condensed Matter Physics ,Directed percolation ,Electronic, Optical and Magnetic Materials ,Variational method ,Percolation ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Density of states - Abstract
A novel variational method is proposed for calculating the percolation threshold, the real-space structure, and the thermodynamical compressibility of a disordered two-dimensional electron liquid. Its high accuracy is verified against prior numerical results and newly derived exact asymptotics. The inverse compressibility is shown to have a strongly asymmetric minimum at a density that is approximately the triple of the percolation threshold. This implies that the experimentally observed metal-insulator transition takes place well before the percolation point is reached., 4 pages, 2 figures. (v2) minor changes (v3) reference added (v4) few more references added
- Published
- 2004
19. Erratum: Cyclotron Resonance in a Two-Dimensional Electron Gas with Long-Range Randomness [Phys. Rev. Lett. 80, 4749 (1998)]
- Author
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Boris I Shklovskii and Michael M. Fogler
- Subjects
Physics ,Range (particle radiation) ,Condensed matter physics ,Cyclotron resonance ,General Physics and Astronomy ,Atomic physics ,Randomness ,Fourier transform ion cyclotron resonance ,Ion cyclotron resonance ,Electron cyclotron resonance - Published
- 1998
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