Phonon-bottlenecked spin relaxation of Er${}^{3+}$:CaWO${}_4$ at milliKelvin temperatures

S. Rajendran, B. Mistri, P. K. Sharma +5

We study spin-lattice relaxation times of electron spins in Er${}^{3+}$:CaWO${}_4$ at millikelvin temperature, detected via their coupling to a low-mode volume superconducting resonato…