Commensurate-incommensurate transitions of quantum Hall stripe states in double-quantum-well systems

TL;DR

This paper investigates the complex phase transitions of stripe states in double-quantum-well systems under parallel magnetic fields, revealing rich phase diagrams and distinct collective excitations through Hartree-Fock analysis.

Contribution

It introduces a detailed Hartree-Fock study of commensurate-incommensurate transitions in quantum Hall stripe states influenced by parallel magnetic fields.

Findings

Identification of a rich phase diagram with multiple transitions.

Oscillations in tunneling matrix elements induce complex phase sequences.

Distinct collective excitations differentiate homogeneous and stripe states.

Abstract

In higher Landau levels (N>0) and around filling factors nu =4N+1, a two-dimensional electron gas in a double-quantum-well system supports a stripe groundstate in which the electron density in each well is spatially modulated. When a parallel magnetic field is added in the plane of the wells, tunneling between the wells acts as a spatially rotating effective Zeeman field coupled to the ``pseudospins'' describing the well index of the electron states. For small parallel fields, these pseudospins follow this rotation, but at larger fields they do not, and a commensurate-incommensurate transition results. Working in the Hartree-Fock approximation, we show that the combination of stripes and commensuration in this system leads to a very rich phase diagram. The parallel magnetic field is responsible for oscillations in the tunneling matrix element that induce a complex sequence of transitions between commensurate and incommensurate liquid or stripe states. The homogeneous and stripe states we find can be distinguished by their collective excitations and tunneling I-V, which we compute within the time-dependent Hartree-Fock approximation.