Pressure effect on low-temperature photoluminescence of the SiV, GeV, and SnV color centers in high-pressure high-temperature diamonds

Here we report the hydrostatic pressure effect on low-temperature (80 K) photoluminescence of high-pressure high-temperature diamonds with SiV, GeV, and SnV color centers. A linear blueshift in the zero-phonon line (ZPL) energy with increasing pressure was observed for all centers. The pressure coefficients of SiV, GeV, and SnV were found to increase in the order of increasing dopant mass with a noticeable jump at the transition between SiV and GeV and just a slight increase at the transition between GeV and SnV. The low-temperature conditions of our measurements and the high quality of the studied samples also allowed us to investigate the pressure effect on the quasilocal vibrational modes (QLVMs) of SiV and GeV. Both QLVM's energies were found to increase with pressure, and a method for estimating internal strain based on this phenomenon was proposed. At the same time, the pressure coefficient of the SiV QLVM energy appeared to be almost 3 times as much as for the GeV, while the situation for the pressure coefficients of ZPLs is reversed. The obtained experimental data were summarized on a configurational diagram within the Franck-Condon approximation, and the pressure effect on adiabatic potentials was shown. In addition, we studied the pressure effect on the PL of some co-occurring color centers [720 nm and nitrogen-vacancy centers ($\mathrm{N}{\mathrm{V}}^{\ensuremath{-}}$ and $\mathrm{N}{\mathrm{V}}^{0}$)], also presented in the studied diamond samples. For the 720 nm center the noticeable change of the ZPL shape was demonstrated already at $P=4.64\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, which may signal the outstanding (in comparison to other color centers) pressure sensitivity of its electronic structure. Finally, the pressure coefficients of the studied color centers were used to compare the possible impact of the local stress distribution within the diamond sample on the inhomogeneous broadening of the ZPL.