Interaction Effects at Crossings of Spin-Polarised One-Dimensional Subbands

TL;DR

This study investigates how spin-polarised 1D subbands in GaAs/AlGaAs heterostructures interact at crossings under magnetic fields, revealing spontaneous spin splitting and conductance features related to the 0.7 structure.

Contribution

It provides new insights into the interaction effects and spontaneous spin splitting at subband crossings in 1D systems under magnetic fields.

Findings

Spontaneous splitting at subband crossings leads to additional conductance features.

Conductance structures evolve from 1.5 to 2e^2/h with increasing magnetic field.

Characteristics of the 0.7 structure are observed at higher temperatures and fields.

Abstract

We report conductance measurements of ballistic one-dimensional (1D) wires defined in GaAs/AlGaAs heterostructures in an in-plane magnetic field, B. When the Zeeman energy is equal to the 1D subband energy spacing, the spin-split subband N(up-spin) intersects (N+1)(down-spin), where N is the index of the spin-degenerate 1D subband. At the crossing of N=1(up-spin) and N=2(down-spin) subbands, there is a spontaneous splitting giving rise to an additional conductance structure evolving from the 1.5(2e^2/h) plateau. With further increase in B, the structure develops into a plateau and lowers to 2e^2/h. With increasing temperature and magnetic field the structure shows characteristics of the 0.7 structure. Our results suggest that at low densities a spontaneous spin splitting occurs whenever two 1D subbands of opposite spins cross.