Pressure evolution of the normal- and superconducting-state properties of the line-nodal material CaSb${}_2$ revealed by ${}^{123}$Sb nuclear quadrupole resonance

Abstract

CaSb${}_2$ is the Dirac line-nodal material that exhibits a superconducting (SC) transition at 1.7 K. In spite of its conventional SC state at ambient pressure, the transition temperature $T_{\mathrm{c}}$ shows a peak structure against hydrostatic pressure. We performed ac magnetic susceptibility and ${}^{123}$Sb nuclear quadrupole resonance (NQR) measurements on single-crystalline CaSb${}_2$ under pressures up to 2.08 GPa. $T_{\mathrm{c}}$ monotonically increased in this pressure region, which is consistent with a previous study. We observed continuous broadening of the NQR spectrum against pressure, which is a sign of unique compression behavior of the lattice. In the normal state, the nuclear spin-lattice relaxation rate 1/$T_1$ is proportional to temperature in all pressure values; typical of a metal. However, 1/$T_{1}T$ in the normal state is independent of pressure, indicating that the density of states at the Fermi energy $N(E_{\mathrm{F}})$, which is one of the parameters governing $T_{\mathrm{c}}$, is insensitive to pressure. From these results, we conclude that $N(E_{\mathrm{F}})$ does not govern the origin of the enhancement in $T_{\mathrm{c}}$. This is unusual for a weak electron-phonon coupling superconductor. In the SC state, we revealed that the SC gap becomes larger and more isotropic under pressure.

6 pages, 4 figures

References in corpus (8)

• Type I superconductivity in the Dirac semimetal PdTe2
• Superconductivity and Fermi Surface Nesting in the Candidate Dirac Semimetal NbC
• Pressure-induced unconventional superconductivity in the heavy-fermion antiferromagnet CeIn3: An 115In-NQR study under pressure
• S-wave Superconductivity in the Dirac Line-nodal Material CaSb2
• Peak in the superconducting transition temperature of the nonmagnetic topological line-nodal material CaSb${}_2$ under pressure
• Quasi-2D Fermi surface of superconducting line-nodal metal CaSb${}_2$
• Bulk Superconductivity in the Dirac Semimetal TlSb
• Fermiology of a topological line-nodal compound CaSb2 and its implication to superconductivity: angle-resolved photoemission study

Cited by in corpus (1)

• Subtle Structural Anomaly under Compression in Line-Nodal CaSb${}_2$