Center for Artificial Low Dimensional Electronic Systems

Tuning Quantum Transport and Interference in Topological Nanowires

Vincent Sacksteder

September 12(Mon) - September 12(Mon), 2016

Tuning Quantum Transport and Interference in Topological Nanowires

Dr. Vincent Sacksteder (Royal Holloway Univ.)

We study the magnetoconductance of topological insulator nanowires in a longitudinal magnetic field, including Aharonov-Bohm, Altshuler-Aronov-Spivak, perfectly conducting channel, and universal conductance fluctuation effects. Our focus is on predicting experimental behavior in single wires in the quantum limit where temperature is reduced to zero.

We show that changing the Fermi energy $E_F$ can tune a wire from ballistic to diffusive conduction and to localization. In both ballistic and diffusive single wires we find both Aharonov-Bohm and Altshuler-Aronov-Spivak oscillations with similar strengths, accompanied by strong universal conductance fluctuations, all with amplitudes between $0.3 , G_0$ and $1,G_0$. This contrasts strongly with the average behavior of many wires, which shows Aharonov-Bohm oscillations in the ballistic regime and Altshuler-Aronov-Spivak oscillations in the diffusive regime.

In single wires the ballistic and diffusive regimes can be distinguished by varying $E_F$ and studying the sign of the AB signal, which depends periodically on $E_F$ in ballistic wires and randomly on $E_F$ in diffusive wires. We also show that in long wires the perfectly conducting channel is visible at a wide range of energies within the bulk gap, and we present

typical conductance profiles at several wire lengths. Similar behavior will be found in carbon nanotubes.