Spin relaxation in a single-electron graphene quantum dot

TL;DR

This paper reports long spin relaxation times exceeding 200 microseconds in bilayer graphene quantum dots, highlighting graphene's potential as a scalable platform for solid-state spin qubits due to its low spin-orbit and hyperfine interactions.

Contribution

It provides the first measurement of spin relaxation times in bilayer graphene quantum dots, demonstrating significantly longer $T_1$ times than previous carbon-based quantum dots.

Findings

Relaxation times exceed 200 microseconds at 1.9 T.

$T_1$ depends strongly on spin splitting.

Longer $T_1$ expected at lower magnetic fields.

Abstract

The relaxation time of a single-electron spin is an important parameter for solid-state spin qubits, as it directly limits the lifetime of the encoded information. Thanks to the low spin-orbit interaction and low hyperfine coupling, graphene and bilayer graphene (BLG) have long been considered promising platforms for spin qubits. Only recently, it has become possible to control single-electrons in BLG quantum dots (QDs) and to understand their spin-valley texture, while the relaxation dynamics have remained mostly unexplored. Here, we report spin relaxation times ($T_1$) of single-electron states in BLG QDs. Using pulsed-gate spectroscopy, we extract relaxation times exceeding 200 $\mu$s at a magnetic field of 1.9 T. The $T_1$ values show a strong dependence on the spin splitting, promising even longer $T_1$ at lower magnetic fields, where our measurements are limited by the signal-to-noise ratio. The relaxation times are more than two orders of magnitude larger than those previously reported for carbon-based QDs, suggesting that graphene is a potentially promising host material for scalable spin qubits.