Conductance anomalies in nanoscale quantum point contact devices on an undoped GeSn/Ge heterostructure

GeSn is a promising material for quantum and spintronic applications due to its strong Rashba spin-orbit coupling (SOC) strengths. In this work, we present quantized conductance in a gated quantum point contact (QPC) device on an undoped Ge_0.94Sn_0.06/Ge heterostructure. We perform DC measurements at 1.5 K to verify the control ability of split gates in the QPC device. We then perform differential-conductance measurements at 120 mK and characterize the nonlinear transport properties by sweeping the source-to-drain bias under different split-gate voltages. We observed 0.7 G₀ and 0.35 G₀ zero-bias conductance anomalies without an external magnetic field. By applying an out-of-plane magnetic field of 3 T, clearer 0.7 G₀ and 0.35 G₀ conductance plateaus are observed. Under a magnetic field of 8 T, we observed a clear 0.5 G₀ plateau, which might be attributed to the lifted spin degeneracy by the Zeeman effect.