Near-Surface Structural Phase Transition of SrTiO${}_3$ Studied with Zero-Field $\beta$-Detected Nuclear Spin Relaxation and Resonance

We demonstrate that zero-field $\beta$-detected nuclear quadrupole resonance and spin relaxation of low energy ${}^8$Li can be used as a sensitive local probe of structural phase transitions near a surface. We find that the transition near the surface of a SrTiO${}_3$ single crystal occurs at $T_c\sim 150$ K, i.e., 45 K higher than $T_c^{bulk}$, and that the tetragonal domains formed below $T_c$ are randomly oriented.