Interaction Effects in a One-Dimensional Constriction

TL;DR

This paper investigates the 0.7 conductance anomaly in one-dimensional GaAs/AlGaAs constrictions, revealing its relation to spin effects and electron-electron interactions through extensive experimental analysis.

Contribution

It provides new insights into the origin of the 0.7 structure, demonstrating its connection to spin and many-body interactions in 1D quantum wires.

Findings

The 0.7 structure is not due to transmission or resonance effects.

All 1D subbands exhibit Zeeman splitting at high magnetic fields.

Electron-electron interactions influence the last few 1D subbands.

Abstract

We have investigated the transport properties of one-dimensional (1D) constrictions defined by split-gates in high quality GaAs/AlGaAs heterostructures. In addition to the usual quantized conductance plateaus, the equilibrium conductance shows a structure close to $0.7(2e^2/h)$, and in consolidating our previous work [K.~J. Thomas et al., Phys. Rev. Lett. 77, 135 (1996)] this 0.7 structure has been investigated in a wide range of samples as a function of temperature, carrier density, in-plane magnetic field $B_{\parallel}$ and source-drain voltage $V_{sd}$. We show that the 0.7 structure is not due to transmission or resonance effects, nor does it arise from the asymmetry of the heterojunction in the growth direction. All the 1D subbands show Zeeman splitting at high $B_{\parallel}$, and in the wide channel limit the $g$-factor is $\mid g \mid \approx 0.4$, close to that of bulk GaAs. As the channel is progressively narrowed we measure an exchange-enhanced $g$-factor. The measurements establish that the 0.7 structure is related to spin, and that electron-electron interactions become important for the last few conducting 1D subbands.