Evolution of the nu = 1 Ground-State in Coupled Double Quantum Wells: Optical Evidence for Broken-Symmetry States

TL;DR

This study uses magneto-absorption spectroscopy to investigate the evolution of the ground state in coupled double quantum wells at nu=1, revealing the interplay of tunneling, Coulomb interactions, and quantum fluctuations affecting the many-body ground state.

Contribution

First optical evidence showing the transition from tunneling-dominated to Coulomb-interaction-dominated ground states in coupled quantum wells at nu=1.

Findings

Spectra indicate a ground-state transition influenced by Coulomb effects.

Evidence that the nu=1 state is not fully pseudospin polarized.

Quantum fluctuations significantly affect the ground-state properties.

Abstract

We present the first magneto-absorption studies of coupled electron double layers in the quantum Hall regime. Optical absorption spectra in the vicinity of total filling factor nu = 1 reveal intriguing behavior that have no analog in the single electron layer nu = 1 state and demonstrate the interplay between single-particle tunneling and inter-layer Coulomb effects. The spectra provide direct evidence of a ground-state that evolves from a region dominated by single-particle tunneling to a regime in which inter-layer Coulomb interactions determine the nature of the ground-state. Moreover the spectra provide the first direct evidence that the incompressible ground-state at nu = 1 in the many-body regime is not fully pseudospin polarized and is sensitive to the effects of quantum fluctuations in the pseudospin variable.