Spectral diffusion of phosphorus donors in silicon at high magnetic field

TL;DR

This study investigates the phase memory time of phosphorus donor electron spins in silicon at high magnetic fields, revealing effects of spectral diffusion influenced by silicon-29 nuclei and optical excitation.

Contribution

It provides new measurements of spectral diffusion times at high magnetic fields and explores the impact of optical excitation on these times in silicon doped with phosphorus.

Findings

Spectral diffusion time (T_SD) is 124 μs at high field in the dark.

Optical excitation increases T_SD to 201 μs.

High magnetic field reduces T_SD compared to low field.

Abstract

We characterize the phase memory time of phosphorus donor electron spins in lightly-doped natural silicon at high magnetic field (8.58 T) in the dark and under low-power optical excitation. The spin echo decays are dominated by spectral diffusion due to the presence of the 4.7% abundant spin-1/2 silicon-29 nuclei. At 4.2 K, the spectral diffusion time (T$_{SD}$) measured in the dark is $124 \pm 7$ $\mu$s, a factor of 2 smaller than that measured at low magnetic fields (0.35 T). Using a tunable laser we also measured the echo decay as the wavelength of the optical excitation is swept across the band edge from 1050 nm to 1090 nm. Above-bandgap optical excitation is seen to increase the spectral diffusion time of the donor electron spin to $201 \pm 11$ $\mu$s. The physical mechanism underlying both the decrease of T$_{SD}$ at high field and the subsequent increase under optical excitation remains unclear.