Investigating Energy Scales of Fractional Quantum Hall States using Scanning Gate Microscopy

TL;DR

This study employs scanning gate microscopy at ultra-low temperatures to locally induce and analyze fractional quantum Hall states, revealing the activation energy and its dependence on local potential landscapes.

Contribution

It introduces a method to measure local activation energies of fractional quantum Hall states using scanning gate microscopy at 35 mK.

Findings

Activation energy at 6 T is between 153 and 194 μeV.

Activation energy is about 50% lower than in bulk samples.

Activation energy is independent of the confining potential shape.

Abstract

We use the voltage biased tip of a scanning force microscope at a temperature of 35\,mK to locally induce the fractional quantum Hall state of $\nu=1/3$ in a split-gate defined constriction. Different tip positions allow us to vary the potential landscape. From temperature dependence of the conductance plateau at $G=1/3 \times e^2/h$ we determine the activation energy of this local $\nu=1/3$ state. We find that at a magnetic field of 6\,T the activation energy is between 153\,$\mu$eV and 194\,$\mu$eV independent of the shape of the confining potential, but about 50\% lower than for bulk samples.