Quantum Solid Phase and Coulomb Drag in 2D Electron–Electron Bilayers of MoS2

Abstract

Coulomb drag experiments can give information about the interaction state of double-layer systems. Here, anomalous Coulomb drag behaviors are demonstrated in a 2D 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 behavior 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. Quantum solid/fluid phases and the Kosterlitz–Thouless/Wigner 2D quantum melting transition are investigated in this bilayer system and this interesting phenomenon is described 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.