36 research outputs found
Non-analytic Vortex Core and a Nonlinear Vortex Flow in Bosonic Superfluids
We analyze the disorder limited motion of quantum vortices in a
two-dimensional bosonic superfluid with a large healing length. It is shown
that the excitations of low-energy degrees of freedom associated with the
non-analytic reconstruction of the vortex core [Ann. Phys. {\bf 346}, 195
(2014)] determine strong non-linear effects in the vortex transport at
velocities much smaller than Landau's critical velocity. Experiments are
suggested to verify our predictions.Comment: 5 pages, 3 figure
Microscopic model of quantum butterfly effect: out-of-time-order correlators and traveling combustion waves
We extend the Keldysh technique to enable the computation of out-of-time
order correlators. We show that the behavior of these correlators is described
by equations that display initially an exponential instability which is
followed by a linear propagation of the decoherence between two initially
identically copies of the quantum many body systems with interactions. At large
times the decoherence propagation (quantum butterfly effect) is described by a
diffusion equation with non-linear dissipation known in the theory of
combustion waves. The solution of this equation is a propagating non-linear
wave moving with constant velocity despite the diffusive character of the
underlying dynamics. Our general conclusions are illustrated by the detailed
computations for the specific models describing the electrons interacting with
bosonic degrees of freedom (phonons, two-level-systems etc.) or with each
other
Strained bilayer graphene: Band structure topology and Landau level spectrum
We show that topology of the low-energy band structure in bilayer graphene
critically depends on mechanical deformations of the crystal which may easily
develop in suspended graphene flakes. We describe the Lifshitz transition that
takes place in strained bilayers upon splitting the parabollic bands at
intermediate energies into several Dirac cones at the energy scale of few meV.
Then, we show how this affects the electron Landau level spectra and the
quantum Hall effect.Comment: slightly over 4 pages, 3 figures, updated discussion and references;
almost identical to the published versio
Auger recombination of dark excitons in and monolayers
We propose a novel phonon assisted Auger process unique to the electronic
band structure of monolayer transition metal dichalcogenides (TMDCs), which
dominates the radiative recombination of ground state excitons in Tungsten
based TMDCs. Using experimental and DFT computed values for the exciton
energies, spin-orbit splittings, optical matrix element, and the Auger matrix
elements, we find that the Auger process begins to dominate at carrier
densities as low as , thus providing a plausible
explanation for the low quantum efficiencies reported for these materials.Comment: 5 pages, 2 figure