Universality in an integer Quantum Hall transition

TL;DR

This study observes a universal quantum critical behavior in an integer Quantum Hall transition, with conductivities near expected values, suggesting a common underlying mechanism across different quantum phase transitions.

Contribution

It demonstrates universal critical behavior in an integer Quantum Hall transition, linked to short-range disorder, which had not been clearly established before.

Findings

Conductivities at critical point close to theoretical values

Scattering parameter depends exponentially on filling factor

Universal behavior observed across different quantum transitions

Abstract

An integer Quantum Hall effect transition is studied in a modulation doped p-SiGe sample. In contrast to most examples of such transitions the longitudinal and Hall conductivities at the critical point are close to 0.5 and 1.5 (e^2/h), the theoretically expected values. This allows the extraction of a scattering parameter, describing both conductivity components, which depends exponentially on filling factor. The strong similarity of this functional form to those observed for transitions into the Hall insulating state and for the B=0 metal- insulator transition implies a universal quantum critical behaviour for the transitions. The observation of this behaviour in the integer Quantum Hall effect, for this particular sample, is attributed to the short-ranged character of the potential associated with the dominant scatterers.