Phase-Sensitive Probes of Nuclear Polarization in Spin-Blockaded Transport

TL;DR

This paper demonstrates a method to electrically detect phase-sensitive nuclear-spin dynamics in spin-blockaded quantum dots by exploiting interference between hyperfine and spin-orbit interactions, revealing nuclear precession effects.

Contribution

It introduces a novel electrical detection technique for coherent nuclear-spin dynamics based on interference effects in spin-blockaded quantum dots.

Findings

Nuclear precession causes oscillations in nuclear-spin pumping rate.

Interference between hyperfine and spin-orbit interactions modulates electron-spin-flip rates.

The method enables phase-sensitive detection of nuclear polarization in nanoscale systems.

Abstract

Spin-blockaded quantum dots provide a unique setting for studying nuclear-spin dynamics in a nanoscale system. Despite recent experimental progress, observing phase-sensitive phenomena in nuclear spin dynamics remains challenging. Here we point out that such a possibility opens up in the regime where hyperfine exchange directly competes with a purely electronic spin-flip mechanism such as the spin-orbital interaction. Interference between the two spin-flip processes, resulting from long-lived coherence of the nuclear-spin bath, modulates the electron-spin-flip rate, making it sensitive to the transverse component of nuclear polarization. In a system repeatedly swept through a singlet-triplet avoided crossing, nuclear precession is manifested in oscillations and sign reversal of the nuclear-spin pumping rate as a function of the waiting time between sweeps. This constitutes a purely electrical method for the detection of coherent nuclear-spin dynamics.