1. Elastic Softening in Synthetic Diamonds
- Author
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Yanagisawa, Tatsuya, Hibino, Ruo, Hidaka, Hiroyuki, Amitsuka, Hiroshi, Tashima, Toshiyuki, Akatsu, Mitsuhiro, Nemoto, Yuichi, Zherlitsyn, Sergei, and Wosnitza, Joachim
- Subjects
Condensed Matter - Materials Science ,Condensed Matter - Strongly Correlated Electrons ,Physics - Applied Physics - Abstract
This study reveals a novel phenomenon demonstrating the elastic softening of synthetic diamonds when cooled to very low temperatures below 1 K. We present the results of ultrasonic measurements of single-crystalline synthetic diamonds without irradiation, namely type-IIa (colorless) and Ib (yellow) diamonds grown by high-pressure-high-temperature synthesis as well as type-IIa diamond grown by chemical vapor deposition. We observed a divergent decrease of the elastic stiffness constant $C_{44}$ in all samples at low temperatures down to 20 mK. We argue for the existence of electric quadrupolar degrees of freedom with irreducible representation $T_2$ in diamond as the origin of this elastic softening. The possible ground state preserves local $T_d$ symmetry presumably down to absolute zero. Of the ground states of atomic vacancies in diamond proposed thus far, the only relevant one is the positively charged single atomic vacancy V$^+$, which has not been observed in previous optical measurements in diamonds., Comment: 8 Pages, 3 figures with supplemental materials
- Published
- 2024