Quantum solid phase and Coulomb drag in two-dimensional electron-electron bilayers of MoS2

TL;DR

This study explores anomalous Coulomb drag behaviors in a two-dimensional MoS2 bilayer system, revealing quantum solid phases and phase transitions that challenge conventional Fermi-liquid models at low temperatures.

Contribution

It demonstrates the existence of quantum solid and melting phases in MoS2 bilayers and links these to unusual Coulomb drag behaviors not explained by traditional models.

Findings

Observation of Coulomb drag upturn at low temperatures

Identification of quantum solid and melting phases

Correlation with thermally activated quantum defects

Abstract

Coulomb drag experiments can give us information about the interaction state of double-layer systems. Here, we demonstrate anomalous Coulomb drag behaviours in a two-dimensional electron-electron bilayer system constructed by stacking atomically thin MoS2 on opposite sides of thin dielectric layers of boron nitride. In the low temperature regime, the measured drag resistance does not follow the behaviour predicted by the Coulomb drag models of exchanging momenta and energies with the particles in Fermi-liquid bilayer systems. Instead, it shows an upturn to higher and higher values. We investigate quantum solid/fluid phases and the Kosterlitz-Thouless/Wigner two-dimensional quantum melting transition in this bilayer system and describe this interesting phenomenon based on thermally activated carriers of quantum defects from the formation of the correlation-induced electron solid phases with enhanced stabilization by the potential due to the boron nitride dielectric layers.