Interlayer Coherence in the $\nu=1$ and $\nu=2$ Bilayer Quantum Hall States

TL;DR

This study investigates the phase transitions and coherence properties of bilayer quantum Hall states at filling factors 1 and 2 through experimental measurements of Hall-plateau widths and activation energies, revealing new phase states.

Contribution

It provides new experimental evidence of phase transitions and identifies three distinct $ u=2$ bilayer quantum Hall states, including the first discovery of a coherent incommensurate state.

Findings

Confirmed phase transition at $ u=1$ and discovered at $ u=2$

Identified three $ u=2$ states: compound, coherent commensurate, and coherent incommensurate

Measured Hall-plateau widths and activation energies under varying conditions

Abstract

We have measured the Hall-plateau width and the activation energy of the bilayer quantum Hall (BLQH) states at the Landau-level filling factor $\nu=1$ and 2 by tilting the sample and simultaneously changing the electron density in each quantum well. The phase transition between the commensurate and incommensurate states are confirmed at $\nu =1$ and discovered at $\nu =2$. In particular, three different $\nu =2$ BLQH states are identified; the compound state, the coherent commensurate state, and the coherent incommensurate state.