Development of the tunnelling gap in disordered 2D electron system with magnetic field: observation of the soft-hard gap transition

TL;DR

This study investigates how magnetic fields influence tunneling gaps in disordered 2D electron systems, revealing a transition from a soft to a hard gap as the magnetic field increases beyond 13 T.

Contribution

It provides experimental evidence of the soft-hard gap transition in disordered 2D electron systems under magnetic fields, highlighting the evolution of the tunneling density of states.

Findings

Magnetic field induces a soft tunneling gap centered at the Fermi level.

The soft gap has a linear form with finite TDOS diminishing with B.

Transition to a hard gap occurs at B > 13 T, where TDOS vanishes around the Fermi level.

Abstract

Magnetic field suppression of the tunneling between disordered 2D electron systems in GaAs around zero bias voltage has been studied. Magnetic field B normal to the layers induces a dip in the tunneling density of states (TDOS) centered precisely at the Fermi level, i.e. soft tunneling gap. The soft gap has a linear form with finite TDOS diminishing with B at the Fermi level. Driven by magnetic field the transition soft-hard gap has been observed, i.e. the TDOS vanishes in the finite energy window around Fermi level at B>13 T.