Hyperfine and nuclear quadrupole splitting of the NV− ground state in 4H -SiC

Abstract

Optically addressable spin-triplet defects in silicon carbide, such as divacancies and negatively charged nitrogen vacancy $({\mathrm{NV}}^{\ensuremath{-}})$ allow to develop modern quantum technologies operating in the near-infrared range based on the well-developed semiconductor material. Here, by means of both high-frequency (94 GHz) pulsed electron paramagnetic resonance (EPR) and electron-nuclear double Rresonance (ENDOR) techniques the ground state properties of the negatively charged ${\mathrm{NV}}^{\ensuremath{-}}$ defect in $4H$-SiC were studied. We experimentally determined the ordering of the ground state spin sublevels and established the sign of the zero-field splitting to be positive as predicted by theory. Analysis of nuclear magnetic resonance transitions in ENDOR spectra allowed to determine the sign, symmetry, and absolute values of the hyperfine interaction of the ${\mathrm{NV}}^{\ensuremath{-}}$ defect electron spin with $^{14}\mathrm{N}$ nuclear spin as ${\mathit{A}}_{\ensuremath{\parallel}}=\ensuremath{-}1.142\phantom{\rule{4pt}{0ex}}\mathrm{MHz}$ and ${\mathit{A}}_{\ensuremath{\perp}}=\ensuremath{-}1.184\phantom{\rule{4pt}{0ex}}\mathrm{MHz}$. The absolute value of the nuclear quadrupole interaction constant reflecting an interaction between the $^{14}\mathrm{N}$ nuclear electric quadrupole moment with the electric field gradient was determined to be $|{\mathit{C}}_{q}|=2.44\phantom{\rule{4pt}{0ex}}\mathrm{MHz}$. This large value is compatible with a threefold coordinated $^{14}\mathrm{N}$ nucleus with uniaxial symmetry and proves conclusively the existence of a nearestneighbor ${\mathrm{N}}_{\mathrm{C}}{\mathrm{V}}_{\mathrm{Si}}$ pair in the material. For this ${\mathrm{NV}}^{\ensuremath{-}}$ defect, an ensemble (Hahn-echo) coherence time of ${\mathit{T}}_{\text{2}}=49\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{s}$ was measured, a value which is in the range previously reported for silicon vacancy spin ensembles and slightly longer than ${\mathit{T}}_{\text{2}}=40\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{s}$ measured here on the divacancy spin ensemble.