Quantum point contacts with spin-orbit coupling

Together with Florian Bauer, Jan Heyder and Jan von Delft I studied how spin-orbit effects influence the conductance properties of a quantum point contact. Quantum point contacts are short, narrow channels which conduct electrons in a quantized manner. But in the first conductance step something unusual happens. There is an unexpected reduction in the conductance at around 70% of its top value, called the 0.7-anomaly. To explain the origin of this anomaly it is crucial to take into account interactions between the electrons flowing through the channel. Once we add spin-orbit effects the situation becomes more complicated. We discovered that the spin-orbit field, together with an external magnetic field, can influence the location and shape of the 0.7-anomaly by mimicking and enhancing the effect of electron interactions. We set up a conceptual framework for analyzing the interplay of spin-orbit, electron interactions and the electrostatic landscape of the system, which can explain and predict these effects in realistic devices.

Recently our theoretical predictions were confirmed in an experiment with GaAs quantum point contacts.

Comparison of measured 1D transconductance to tight-binding numerical calculations

Comparison of measured 1D transconductance to tight-binding numerical calculations, Fig. 3 from [Hudson, K.L., Srinivasan, A., Goulko, O. et al. New signatures of the spin gap in quantum point contacts. Nat Commun 12, 5 (2021)]