Influence of topological excitations on Shapiro steps and microwave dynamical conductance in bilayer exciton condensates

TL;DR

This paper investigates how topological defects called merons affect the microwave response and Shapiro steps in bilayer exciton condensates at quantum Hall state a71, revealing that Shapiro steps and Josephson oscillations persist despite disorder.

Contribution

It demonstrates the persistence of Shapiro steps and Josephson oscillations in the presence of merons, contrasting with previous expectations of their suppression due to disorder.

Findings

Shapiro steps are observed despite merons.

Resonant features in microwave conductance indicate Josephson oscillations.

Disorder-induced topological defects do not eliminate microwave phenomena.

Abstract

The quantum Hall state at total filling factor $\nu_T=1$ in bilayer systems realizes an exciton condensate and exhibits a zero-bias tunneling anomaly, similar to the Josephson effect in the presence of fluctuations. In contrast to conventional Josephson junctions, no Fraunhofer diffraction pattern has been observed, due to disorder induced topological defects, so-called merons. We consider interlayer tunneling in the presence of microwave radiation, and find Shapiro steps in the tunneling current-voltage characteristic despite the presence of merons. Moreover, the Josephson oscillations can also be observed as resonant features in the microwave dynamical conductance.