Coherent population trapping and spin relaxation of a silicon vacancy center in diamond at mK temperatures

TL;DR

This study investigates how lowering temperature to millikelvin levels significantly enhances spin coherence in silicon vacancy centers in diamond, revealing phonon interactions' role in spin relaxation.

Contribution

It provides the first detailed experimental analysis of spin relaxation mechanisms in SiV centers at millikelvin temperatures, highlighting the suppression of phonon-induced dephasing.

Findings

Spin lifetime increases nearly 100-fold below 4 K

Phonon-induced dephasing becomes negligible below 1 K

Two-phonon spin-flip transitions are key in spin relaxation

Abstract

We report experimental studies of coherent population trapping and spin relaxation in a temperature range between 4 K and 100 mK in a silicon vacancy (SiV) center subject to a transverse magnetic field. Near and below 1 K, phonon-induced spin dephasing becomes negligible compared with that induced by the spin bath of naturally abundant 13C atoms. The temperature dependence of the spin dephasing rates agrees with the theoretical expectation that phonon-induced spin dephasing arises primarily from orbital relaxation induced by first order electron-phonon interactions. A nearly 100-fold increase in spin lifetime is observed when the temperature is lowered from 4 K to slightly below 1 K, indicating that two-phonon spin-flip transitions play an essential role in the spin relaxation of SiV ground states.