Elastic Softening in Synthetic Diamonds

Abstract

This study reveals a previously unreported phenomenon: elastic softening of synthetic diamonds at temperatures below 1 K. We present ultrasonic measurements on single-crystalline, non-irradiated synthetic diamonds--namely, type-IIa (colorless) and type-Ib (yellow) diamonds grown by high-pressure high-temperature (HPHT) synthesis, as well as type-IIa diamond grown by chemical vapor deposition (CVD). A pronounced, divergent decrease in the elastic stiffness constant $C_{44}$ was observed in all samples down to 20 mK. We attribute this softening to electric quadrupolar degrees of freedom with irreducible representation $T_2$ in diamond. The microscopic origin of this effect, however, remains unresolved. By analogy with similar behavior observed in silicon, we suggest the presence of an as-yet-unidentified, defect-derived quantum ground state with $T_1$ or $T_2$ symmetry at ppb-level concentrations in all three diamonds studied.

7 Pages, 3 figures with supplemental materials (9 Pages, 2 figures)

References in corpus (9)

• The nitrogen-vacancy colour centre in diamond
• Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km
• Sensitivity Optimization for NV-Diamond Magnetometry
• Chemical vapour deposition synthetic diamond: materials, technology and applications
• Low Temperature Studies of Charge Dynamics of Nitrogen-Vacancy Defect in Diamond
• Near-term quantum-repeater experiments with nitrogen-vacancy centers: Overcoming the limitations of direct transmission
• Tunneling and rattling in clathrate crystal
• First-principles study of the dynamic Jahn-Teller distortion of the neutral vacancy in diamond
• Experimental demonstration of two-photon magnetic resonances in a single-spin-system of a solid