Conductance quantization in cleaved edge overgrowth GaAs quantum wires*

Cleaved Edge Overgrowth (CEO) quantum wires (QW) are among the cleanest 1D systems available, showing conductance quantization and Luttinger liquid effects such as charge fractionalization and spin-charge separation. Previously, we have studied the conductance quantization of CEO QWs as a function of temperature in Scheller et al. PRL112, 066801 (2014), finding that the first wire plateau goes from 2 e²/h at high T > 10K to 1 e²/h at low T < 0.1K. This was interpreted as evidence for a nuclear spin helix, as proposed theoretically by Braunecker, Simon and Loss PRB80, 165119 (2009).
Here, we look at the dependence on wire length, and observe a steeper slope over increasing temperatures in short 2 μm wires compared to 6 μm wires. This is consistent with theory from Aseev et al. PRBB95, 125440 (2017) and may allow an estimate of the Luttinger charge interaction parameter.
Further, we report on the velocities of quantum Hall edge states measured on the same CEO sample using momentum resolved tunneling spectroscopy. Using a multi terminal measurement of the voltage drop, the velocities agree very well with theory. In the future, fractional and topological edge states could be studied with this technique.