Superconductivity in centrosymmetric topological superconductor candidate TaC

Abstract

We report the synthesis and physical properties of the single crystals of TaC, which are proposed to hold topological band structure as a topological superconductor (TSC) candidate. Magnetization, resistivity and specific heat measurements are performed and indicate that TaC is bulk superconductor with critical temperature of 10.3 K. TaC is a strongly coupled type-II superconductor and the superconducting state can be well described by s-wave Bardeen–Cooper–Schrieffer theory with a single gap. The upper critical field (H c2) of TaC shows linear temperature dependence, which is quite different from most conventional superconductors and isostructural NbC, which is proposed to manifest topological nodal-loops or type-II Dirac points as well as superconductivity. Our results suggest that TaC would be a new candidate for further research of TSCs.

Discovery of the High‐Entropy Carbide Ceramic Topological Superconductor Candidate (Ti0.2Zr0.2Nb0.2Hf0.2Ta0.2)C

“…[ 26 ] When the e/a increase to 4.2 of (Ti 0.2 Zr 0.2 Nb 0.2 Hf 0.2 Ta 0.2 )C HEC, the T c is 2.35 K. The VB‐IVA and VB‐VA compounds NbC, TaC, ZrN, and HfN have 4.5 e/a and high T c values. [ 24,40 ] The highest T c found up to now for TMMCs, and TMMNs are ≈18 K for pseudo‐binary systems (NbN) 0.8 (TiC) 0.2 and NbC 0.3 N 0.7 , [ 26 ] which have 4.8 and 4.85 e/a, respectively. According to Matthias' rule [ 31 ] and the study of SC in interstitial compounds with NaCl‐type structure, [ 26 ] when the electrons per atom are >4.8, the T c decreases.…”

“…[23] Moreover, the type-II Dirac semimetal states were proposed to exist in the band structure of TaC, which is a relatively high T c ≈10.6 K superconductor. [24,25] However, TiC, ZrC, and HfC, which have 4 VEC per atom, are non-superconducting. [26] HECs have entered the fray and garnered increasing interest from 2015 onward.…”

Superconductivity and topological states in hexagonal TaC and NbC

“…34 In addition, the isostructural TaC is proposed as a topological superconductor candidate. 38 Compared to the NaCl-type TMCs, there is another structure of TMCs with the same crystal structure as y-TaN, 39,40 which exhibits a hexagonal space group. The study of y-TaN type TMCs mainly focuses on the topological properties, such as the triply degenerate nodal topological semimetal of WC, 41,42 the spin-orbit coupling (SOC) induced nodal chain to the Weyl semimetal in HfC, 43 etc.…”

Superconductivity with Topological Non-trivial Surface States in NbC

“…Other TMCs, such as VC [26] and CrC [26], are also predicted to have nontrivial band topology along with bulk superconductivity, but experimental confirmation of their non-trivial topological behavior is yet to be realized. Among these TMCs, the NbC and TaC show superconductivity in range of 8 to 11K [22][23][24][27][28][29]. Most of the Superconductivity reports of these materials are based on polycrystalline samples, as it is difficult to grow their single crystals.…”