Zener tunneling isospin Hall effect in HgTe quantum wells and graphene multilayers

Abstract

A Zener diode is a paradigmatic device in semiconductor-based electronics that consists of a p-n junction where an external electric field induces a switching behavior in the current-voltage characteristics. We study Zener tunneling in HgTe quantum wells and graphene multilayers. We find that the tunneling transition probability depends asymmetrically on the parallel momentum of the carriers to the barrier. In HgTe quantum wells the asymmetry is the opposite for each spin, whereas for graphene multilayers it is the opposite for each valley degree of freedom. In both cases, a spin/valley current flowing in the perpendicular direction to the applied field is produced. We relate the origin of this Zener tunneling spin/valley Hall effect to the Berry phase acquired by the carriers when they are adiabatically reflected from the gapped region.

Valley-selective Landau-Zener oscillations in semi-Dirac p−n junctions

“…The oscillatory tunneling probability depends on the applied bias and the gap, leading to non-monotonic current-voltage response, with negative differential conductance in specific bias regimes. While common-path tunneling interference occurs in any semiconductor 3 , it is subleading to conventional tunneling except near quadratic band crossings -hence its starring role in BLG, versus its relative unimportance in monolayer graphene 4 and conventional semiconductors. This dichotomy is particularly relevant to a new class of 2D semimetals (sometimes termed zero-gap semiconductors) with 'semi-Dirac' dispersion, characterized by electronic bands meeting in a discrete set of nodes about which the bands split linearly or quadratically along independent high-symmetry directions [5][6][7][8] .…”

High-frequency rectification in graphene lateral p-n junctions

“…The dependence I ∝ V 1.5 also follows from theoretical calculations in the ballistic regime, see Refs. [21,22].…”