We measure electron and nuclear spin transition frequencies in the ground state of nitrogen-vacancy (NV) centers in diamond for two nitrogen isotopes ($^{ 14}\mathrm{ NV}$ and $^{ 15}\mathrm{ NV}$) over temperatures ranging from 77 K to 400 K. Measurements are performed using Ramsey interferometry and direct optical readout of the nuclear and electron spins. We extract coupling parameters $Q$ (for $^{ 14}\mathrm{ NV}$), $D$, $A_{ ||}$, $A_{ \perp}$, $\gamma_e/\gamma_n$, and their temperature dependences for both isotopes. The temperature dependences of the nuclear-spin transitions within the $m_s = 0$ spin manifold near room temperature are found to be +0.52(1) ppm/K for $^{ 14}\mathrm{ NV}$ ($|m_I=-1> \leftrightarrow |m_I=+1>$) and -1.1(1) ppm/K for $^{ 15}\mathrm{ NV}$ ($|m_I=-1/2> \leftrightarrow |m_I=+1/2>$). An isotopic shift in the zero-field splitting parameter $D$ between $^{ 14}\mathrm{ NV}$ and $^{ 15}\mathrm{ NV}$ is measured to be $\sim$ 120 kHz. Residual transverse magnetic fields are observed to shift the nuclear spin transition frequencies, especially for $^{ 15}\mathrm{ NV}$. We have precisely determined the set of parameters relevant for the development of nuclear-spin-based diamond quantum sensors with greatly reduced sensitivity to environmental factors.
Categories: quant-ph cond-mat.mes-hall physics.app-ph