Magnon Condensation in a Dense Nitrogen-Vacancy Spin Ensemble

Abstract

The feasibility of creating a Bose-Einstein condensate of magnons using a dense ensemble of nitrogen-vacancy spin defects in diamond is investigated. Through assessing a density-dependent spin exchange interaction strength and the magnetic phase transition temperature ($T_c$) using the Sherrington-Kirkpatrick model, the minimum temperature-dependent concentration for magnetic self-ordering is estimated. For a randomly dispersed spin ensemble, the calculated average exchange constant exceeds the average dipole interaction strengths for concentrations approximately greater than 70 ppm, while $T_c$ is estimated to exceed 10 mK beyond 90 ppm, reaching 300 K at a concentration of approximately 450 ppm. On this basis, the existence of dipole-exchange spin waves and their plane-wave dispersion is postulated and estimated using a semiclassical magnetostatic description. This is discussed along with a $T_c$-based estimate of the four-magnon scattering rate, which indicates magnons and their condensation may be detectable in thin films for concentrations greater than 90 ppm.

14 pages, 6 figures

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• Exciton-polariton condensates
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• Ab initio supercell calculations on nitrogen-vacancy center in diamond: its electronic structure and hyperfine tensors
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Cited by in corpus (2)

• Proximal nitrogen reduces the fluorescence quantum yield of nitrogen-vacancy centres in diamond
• Optical detection of paramagnetic defects in diamond using off-resonance excitation of NV centers