Single-Spin Relaxation in a Synthetic Spin-Orbit Field

Strong magnetic field gradients can produce a synthetic spin-orbit interaction that allows high-fidelity electrical control of single electron spins. We investigate how a field gradient impacts the spin relaxation time T1 by measuring T1 as a function of the magnetic field B in silicon. The interplay of charge noise, magnetic field gradients, phonons, and conduction-band valleys leads to a maximum relaxation time of 160ms at low fields, a strong spin-valley relaxation hotspot at intermediate fields, and a B4 scaling at high fields. T1 is found to decrease with increasing lattice temperature as well as with added electrical noise. In comparison, samples without micromagnets have a significantly greater T1.