Two-step breakdown of a local v = 1 quantum Hall state

TL;DR

This paper investigates the two-step breakdown process of a local v=1 quantum Hall state within a v=2 bulk system, revealing distinct mechanisms at low and high biases through advanced measurement techniques.

Contribution

It introduces a detailed experimental analysis of the two-step breakdown in a local quantum Hall state, combining resistively detected NMR and shot noise measurements.

Findings

Breakdown occurs in two steps at different bias levels.

Inter-edge tunneling causes low-bias breakdown.

Spin gap closure leads to high-bias breakdown.

Abstract

We report quantum Hall effect breakdown of a local filling factor v_local = 1 state formed in a bulk v_bulk = 2 system in an AlGaAs/GaAs heterostructure. When a finite source-drain bias is applied across the local system, the breakdown occurs in two steps. At low bias, quantized conductance through the v_local = 1 system breaks down due to inter-edge electron tunneling. At high bias, the incompressibility of the v_local = 1 system breaks down because the spin gap closes. The two steps are resolved by combining measurements of resistively detected nuclear magnetic resonance and shot noise, which allows one to evaluate electron spin polarization in the local system and spin-dependent charge transport through the system, respectively.