Quantum Interference Effects in Topological Nanowires In a Longitudinal Magnetic Field

摘要

We study the magnetoconductance of topological insulator nanowires in alongitudinal 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 quantumlimit where temperature is reduced to zero. We show that changing the Fermienergy $E_F$ can tune a wire from from ballistic to diffusive conduction and tolocalization. In both ballistic and diffusive single wires we find bothAharonov-Bohm and Altshuler-Aronov-Spivak oscillations with similar strengths,accompanied by quite strong universal conductance fluctuations (UCFs), all withamplitudes between $0.3 \, G_0$ and $1\,G_0$. This contrasts strongly with theaverage behavior of many wires, which shows Aharonov-Bohm oscillations in theballistic regime and Altshuler-Aronov-Spivak oscillations in the diffusiveregime, with both oscillations substantially larger than the conductancefluctuations. In single wires the ballistic and diffusive regimes can bedistinguished by varying $E_F$ and studying the sign of the AB signal, whichdepends periodically on $E_F$ in ballistic wires and randomly on $E_F$ indiffusive wires. We also show that in long wires the perfectly conductingchannel is visible at a wide range of energies within the bulk gap. We presenttypical conductance profiles at several wire lengths, showing that conductancefluctuations can dominate the average signal. Similar behavior will be found incarbon nanotubes.