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R. Bistritzer

Publications and source records attributed to R. Bistritzer.

7 recordsLinked to original sources
arXiv2011

Moire Butterflies

The Hofstadter butterfly spectral patterns of lattice electrons in an external magnetic field yield some of the most beguiling images in physics. Here we explore the magneto-electronic spectra of systems with moire spatial patterns, concentrating on the case of twisted bilayer graphene. Because long-period spatial patterns are accurately formed at small twist angles, fractal butterfly spectra and associated magneto-transport and magneto-mechanical anomalies emerge at accessible magnetic field strengths.

cond-mat.mes-hall↗
arXiv2010

d0 Perovskite-Semiconductor Electronic Structure

We address the low-energy effective Hamiltonian of electron doped d0 perovskite semiconductors in cubic and tetragonal phases using the k*p method. The Hamiltonian depends on the spin-orbit interaction strength, on the temperature-dependent tetragonal distortion, and on a set of effective-mass parameters whose number is determined by the symmetry of the crystal. We explain how these parameters can be extracted from angle resolved photo-emission, Raman spectroscopy, and magneto-transport measurements and estimate their values in SrTiO3.

cond-mat.mtrl-sci↗
arXiv2010

Moire bands in twisted double-layer graphene

A moire pattern is formed when two copies of a periodic pattern are overlaid with a relative twist. We address the electronic structure of a twisted two-layer graphene system, showing that in its continuum Dirac model the moire pattern periodicity leads to moire Bloch bands. The two layers become more strongly coupled and the Dirac velocity crosses zero several times as the twist angle is reduced. For a discrete set of magic angles the velocity vanishes, the lowest moire band flattens, and the Dirac-point density-of-states and the counterflow conductivity are strongly enhanced.

cond-mat.mes-hall↗
arXiv2009

Hydrodynamic theory of transport in doped graphene

We study non-linear dc transport in graphene using a hydrodynamic approach and conclude that in clean samples the drift velocity saturates at a weakly density-dependent value v_{sat} ~ 10^7 cm/s. We show that saturation results from the interactions between graphene's Dirac quasi-particles and both acoustic and optical phonons. Saturation is accompanied by substantial electron heating and is not reached at realistic driving fields in moderately or strongly disordered samples. We find that it is essential to account for interactions among graphene's Dirac quasi-particles, which increase the linear response resistivity at high temperatures or low densities.

cond-mat.other↗
arXiv2009

Electronic Cooling in Graphene

Energy transfer to acoustic phonons is the dominant low-temperature cooling channel of electrons in a crystal.For cold neutral graphene we find that the weak cooling power of its acoustical modes relative to the heat capacity of the system leads to a power law decay of the electronic temperature when far from equilibrium. For heavily doped graphene a high electronic temperature is shown to initially decrease linearly with time at a rate proportional to n^(3/2) with n being the electronic density. We discuss the relative importance of optical and acoustic phonons to cooling.

cond-mat.mes-hall↗
arXiv2008

Influence of Disorder on Electron-Hole Pair Condensation in Graphene Bilayers

Graphene bilayers can condense into a state with spontaneous interlayer phase coherence that supports dissipationless counterflow supercurrents. Here we address the influence of disorder on the graphene bilayer mean-field and Kosterlitz-Thouless critical temperatures and report on a simple criteria for the survival of pair condensation.

cond-mat.mes-hall↗