Observation of Superfluidity and Meissner Effect of Composite Bosons in GaAs Quantum Hall System

TL;DR

This paper provides direct experimental evidence of superfluidity and the Meissner effect in composite bosons within a quantum Hall system, confirming their collective, bulk superfluid nature through charge response measurements.

Contribution

It demonstrates the superfluid nature of composite bosons in quantum Hall systems via charge accumulation and flux response, revealing bulk superfluidity and screening mechanisms.

Findings

Observation of quantized charge accumulation related to flux changes

Charge distribution is uniform across the bulk, indicating collective superfluidity

Screening mechanism depends on the presence of a top gate, showing different regimes

Abstract

The quantum Hall effect (QHE) is theoretically understood as a superfluid condensate of composite bosons (CBs) -- bound states of electrons and magnetic flux quanta. While dissipationless transport is consistent with this picture, other signatures of superfluidity, such as the Meissner effect, remain elusive. Here, we present direct experimental evidence for CB superfluidity by probing the system's response to a controlled, time-varying magnetic field in Corbino disk geometries. We simultaneously observe the quantized Laughlin charge pumping and a new, quantized charge accumulation phenomenon, governed by the relation $\Delta Q_{\rm a}/e = \nu\,(\Delta \Phi/\Phi_0)$. This relation signifies that the system actively maintains the fixed electron-to-flux ratio that defines the CBs, neutralizing excess flux by drawing in a precise number of electrons. Crucially, devices with multiple concentric top gates reveal that this charge accumulation is uniformly distributed across the bulk of the QHE fluid, demonstrating that it is a collective, bulk property rather than an edge effect -- a key signature of a superfluid condensate. Furthermore, the presence of a top gate determines the screening mechanism: in a "grand canonical" setting with a gate, low Coulomb energy favors a charge-mediated screening (generalized Meissner effect); without a gate, the system enters a "canonical" regime, exhibiting fixed electron density like type-II superconductors. These observations confirm the CB superfluid nature of the QHE ground state and establish a versatile platform for studying macroscopic quantum coherence and its screening transitions in two dimensions.