Cooling a mechanical resonator with nitrogen-vacancy centres using a room temperature excited state spin–strain interaction

• Published in: Nature communications Vol. 8; no. 1; p. 14358
• Main Authors: MacQuarrie, E. R., Otten, M., Gray, S. K., Fuchs, G. D.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 06.02.2017; Nature Publishing Group; Nature Portfolio
• Subjects: 639/624/399/1096; 639/766/119/997; 639/766/483/1139; Cooling; Humanities and Social Sciences; MATERIALS SCIENCE; multidisciplinary; Nitrogen; Physics; Protocol; Science; Temperature; New York; United States > US
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms14358

Cooling a mechanical resonator mode to a sub-thermal state has been a long-standing challenge in physics. This pursuit has recently found traction in the field of optomechanics in which a mechanical mode is coupled to an optical cavity. An alternate method is to couple the resonator to a well-controlled two-level system. Here we propose a protocol to dissipatively cool a room temperature mechanical resonator using a nitrogen-vacancy centre ensemble. The spin ensemble is coupled to the resonator through its orbitally-averaged excited state, which has a spin–strain interaction that has not been previously studied. We experimentally demonstrate that the spin–strain coupling in the excited state is 13.5±0.5 times stronger than the ground state spin–strain coupling. We then theoretically show that this interaction, combined with a high-density spin ensemble, enables the cooling of a mechanical resonator from room temperature to a fraction of its thermal phonon occupancy. An efficient cooling mechanism for nanoscale mechanical resonators would help improve their properties for use in sensing applications. Here, the authors demonstrate a strong interaction between NV centres and a resonator and show how it could be harnessed to achieve a large cooling rate.