Tunneling spectroscopy of quantum wires: Spin‐charge separation and localization

Abstract

Using a double wire geometry we probe the quantum many-body modes in ballistic wires and their dependence on Coulomb interactions. The wires are fabricated using the cleaved edge overgrowth method. We clearly observe two spin modes and one charge mode of the coupled wires. We map the dispersion velocities of the modes down to a critical density at which spontaneous localization is observed. Theoretical calculations of the charge velocity agree well with the data, although they also predict an additional charge mode that is not observed. Surprisingly, the suppression of the spin velocities does not depend on density.

Correlation effects in quasi-one-dimensional quantum wires

“…In Sec. IV we interpret the localization transition found in the series of two wire tunneling experiments 6,7,8,9,10,11,12 by studying the evolution of liquid-to-crystal correlations in a finite wire with interactions effectively screened by another parallel wire. We make a comparison between the finite system and the corresponding homogeneous infinite system interacting with the same potential.…”

“…One such technique being cleaved edge overgrowth, which has been applied recently to build an experimental setup with two parallel wires so that it is possible to observe momentum resolved tunneling from one to the other. 6,7,8,9,10,11,12 In this series of experiments both the energy of the tunneling electrons and their momentum could be tuned by changing the relative chemical potential and the applied magnetic field. This setup allows the dispersion relations of each wire to be probed in a quite straightforward manner.…”

“…However, the microscopic details, such as the width and type of the transverse confinement or the distance and shape of neighboring screening media, can have a large impact on the properties of the Q1D systems, as they are very sensitive to the effective interaction. These systems can be realized in semiconductor structures, where there are elegant experimental studies, 6,7,8,9,10,11,12 and it is essential to describe the system accurately for a realistic comparison of theory and experiment.…”