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 (Tc) 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 Tc 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 Tc-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.

Detection of paramagnetic defects in diamond using off-resonance excitation of NV centers

“…In the current study we investigate diamond samples having relatively high density of both NV − and nitrogen 14 substitution (P1) defects. The spin density of our samples is not sufficiently high to allow access to the region where macroscopic magnetic ordering occurs [20], however it is sufficiently high to make χ 1, i.e. to make effects originating from dipolar coupling detectable.…”

Ultrafast Orbital Depolarization and Defect-Localized Phonon Dynamics Induced by Quantum Resonance between Multi-Nitrogen Vacancy Defects

“…Concentration of NV defects drastically changes spin depolarization dynamics, 4,31 NV ionization rates, 21 carrier dynamics under photoexcitation, 32,33 and spectroscopy like fluorescence. 21,34−36 Even applications to heralded two-NVdefect quantum gates 24 as well as the magnon condensation due to dense ensemble of NV defects 4 were recently proposed. However, despite its paramount importance in utilizing this new kind of property in interacting NV defects, the possibilities and roles are not fully understood yet.…”

“…Diamond can stably accommodate a point defect called the nitrogen-vacancy (NV) defect composed of a nitrogen substitution with a nearest-neighbor vacancy. − The NV defect is a leading candidate of building blocks for future quantum computers − and nanoscale sensor devices − because of the promising spin and optical properties, e.g. spin coherences of one second at room temperature and their precise quantum control for an individual NV defect.…”

“…spin coherences of one second at room temperature and their precise quantum control for an individual NV defect. Proximate NV defects with interdefect interaction may further establish a new kind of quantum qubit network in solids and can be a fruitful test to explore controlled multibody quantum dynamics. ,− Recent advances in the ion implantation method, ,,− which is a widely employed strategy to create an NV defect at a precisely controlled location, have made it possible to create more proximate NV defects in a diamond crystal that may interact with each other. Elucidating how proximate NV defects interact and change intrinsic properties of each NV defect is actually becoming a key challenge.…”

“…Elucidating how proximate NV defects interact and change intrinsic properties of each NV defect is actually becoming a key challenge. Concentration of NV defects drastically changes spin depolarization dynamics, , NV ionization rates, carrier dynamics under photoexcitation, , and spectroscopy like fluorescence. ,− Even applications to heralded two-NV-defect quantum gates as well as the magnon condensation due to dense ensemble of NV defects were recently proposed. However, despite its paramount importance in utilizing this new kind of property in interacting NV defects, the possibilities and roles are not fully understood yet.…”