Chang Liu, Xianqi Song, Quan Li,* Yanming Ma* and Changfeng Chen*. Phys. Rev. Lett. 124, 147001, Published 6 April 2020. 

Diamond crystal comprises a carbon bonding network that produces superior mechanical strength and a very large electronic band gap at ambient conditions, making it a superstrong ultrawide band gap semiconductor. Theoretical studies predicted superconductivity in select semiconductors in the early 1960s, but superconducting states in technologically important group-IV semiconductors long eluded experimental detection. Diamond is a prototypical ultrawide band gap semiconductor, but turns into a superconductor with a critical temperature Tc of 4 K near 3% boron doping [E. A. Ekimov et al., Nature (London) 428, 542 (2004)]. Here we unveil a surprising new route to superconductivity in undoped diamond by compression-shear deformation that induces increasing metallization and lattice softening with rising strain, producing phonon mediated Tc up to 2.4–12.4 K. This finding raises intriguing prospects of generating robust superconductivity in strained diamond crystal, showcasing a distinct and hitherto little explored approach to driving materials into superconducting states via strain engineering. These results hold promise for discovering superconductivity in normally nonsuperconductive materials, thereby expanding the landscape of viable nontraditional superconductors and offering actionable insights for experimental exploration.

FIG. 1. (a) The semiconducting, conducting, and superconducting stages of electronic evolution in deformed diamond indicated on the (11-2)[111] CS stress-strain curve. (b) Strain dependence of Tc for a selected range of u*. (c)–(e) Strain evolution of logarithmically averaged phonon frequency ωlog, electronic density of states at the Fermi energy NEF, and electron-phonon coupling parameterλ.

This paper reports a remarkable cooperative effort among 5 laboratories in two countries. Prof. Quan Li and Prof. Yanming Ma, from Jilin University and Prof. Changfeng Chen, from University of Nevada, Las Vegas are the corresponding authors of the paper. Dr. Chang Liu from Jilin University is the first author of this work. Other co-author includes Dr. Xianqi Song from Jilin University.

Read more at Physical Review Letters:
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.124.147001