Kavli Affiliate: Bo Gu
| First 5 Authors: Zheng-Wei Liao, Xin-Wei Yi, Jing-Yang You, Bo Gu, Gang Su
| Summary:
Superconductivity in transition metal nitrides (TMNs) has been investigated
for a long time, such as zirconium nitride (ZrN) with a superconducting
transition temperature Tc of 10 K. Recently, a phase diagram has been revealed
in ZrNx with different nitrogen concentrations, which is very similar to that
of high-temperature copper oxide superconductors. Here, we study the TMNs with
face-centered cubic lattice, where ZrN and HfN have been experimentally
obtained, and predict eight new stable superconductors by the first-principle
calculations. We find that CuN has a high Tc of 39 K with a very strong
electron-phonon coupling (EPC) strength. In contrast to ZrN, CuN has softening
acoustic phonons at the high symmetry point L, which accounts for its much
stronger EPC. In addition, the highly symmetrical structure leads to
topological protected nodal points and lines, such as the hourglass Weyl loop
in kx/y/z = 0 plane and Weyl points in kx/y/z = 2{pi}/a plane, as well as
quadratic band touch at {Gamma} point. CuN could be a topological
superconductor. Our results expand the transition metal nitrides superconductor
family and would be helpful to guide the search for high temperature
topological superconductors.
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