Spin-orbit interaction and anomalous spin relaxation in carbon nanotube quantum dots

TL;DR

This paper investigates spin relaxation in carbon nanotube quantum dots, revealing magnetic field effects, a novel spin-phonon noise spectrum, and electrical control of spin states, with implications for quantum information processing.

Contribution

It predicts ultralong spin relaxation times at specific magnetic fields and introduces a new dissipation channel via a $1/\sqrt{ ext{frequency}}$ noise spectrum.

Findings

Ultralong $T_1$ times exceeding tens of seconds at certain magnetic fields.

Discovery of a $1/\sqrt{ ext{frequency}}$ spin-phonon noise spectrum.

Zero-field level splitting enabling electrical spin control.

Abstract

We study spin relaxation and decoherence caused by electron-lattice and spin-orbit interaction and predict striking effects induced by magnetic fields $B$. For particular values of $B$, destructive interference occurs resulting in ultralong spin relaxation times $T_1$ exceeding tens of seconds. For small phonon frequencies $\omega$, we find a $1/\sqrt{\omega}$ spin-phonon noise spectrum -- a novel dissipation channel for spins in quantum dots -- which can reduce $T_1$ by many orders of magnitude. We show that nanotubes exhibit zero-field level splitting caused by spin-orbit interaction. This enables an all-electrical and phase-coherent control of spin.