Björn Sbierski

Quantum transport of disordered Weyl semimetals at the nodal point.

Weyl semimetals are paradigmatic topological gapless phases in three dimensions. We here address the effect of disorder on charge transport in Weyl semimetals. For a single Weyl node with energy at the degeneracy point and without interactions, theory predicts the existence of a critical disorder strength beyond which the density of states takes on a nonzero value. Predictions for the conductivity are divergent, however. In this work, we present a numerical study of transport properties for a disordered Weyl cone at zero energy. For weak disorder, our results are consistent with a renormalization group flow towards an attractive pseudoballistic fixed point with zero conductivity and a scale-independent conductance; for stronger disorder, diffusive behavior is reached. We identify the Fano factor as a signature that discriminates between these two regimes.

Quantum transport in Dirac materials

We calculate conductance and noise for quantum transport at the nodal point for arbitrarily tilted and anisotropic Dirac or Weyl cones. Tilted and anisotropic dispersions are generic in absence of certain discrete symmetries, such as particle-hole and lattice point group symmetries. Whereas anisotropy affects the conductance g, but leaves the Fano factor F (the ratio of shot noise power and current) unchanged, a tilt affects both g and F. Since F is a universal number in many other situations, this finding is remarkable. We apply our general considerations to specific lattice models of strained graphene and a pyrochlore Weyl semi-metal.

Quantum critical exponents for a disordered three-dimensional Weyl node

Three-dimensional Dirac and Weyl semimetals exhibit a disorder-induced quantum phase transition between a semimetallic phase at weak disorder and a diffusive-metallic phase at strong disorder. Despite considerable effort, both numerically and analytically, the critical exponents

Z2 phase diagram of three-dimensional disordered topological insulators via a scattering matrix approach

\nu

CMOS-based piezo-FET stress sensors in Wheatstone bridge configuration

and

Many-body localization of spinless fermions with attractive interactions in one dimension

z

Disordered double Weyl node: Comparison of transport and density of states calculations

of this phase transition are not known precisely. Here we report a numerical calculation of the critical exponent

Quantitative analytical theory for disordered nodal points

\nu=1.47\pm0.03

Tilted disordered Weyl semimetals

using a minimal single-Weyl node model and a finite-size scaling analysis of conductance. Our high-precision numerical value for

Proposed Rabi-Kondo Correlated State in a Laser-Driven Semiconductor Quantum Dot

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