Fermi surfaces of the topological semimetal CaSn₃ probed through de Haas van Alphen oscillations

Abstract

In the search of topological superconductors, nailing down the Fermiology of the normal state is as crucial a prerequisite as unraveling the superconducting pairing symmetry. In particular, the number of time-reversal-invariant momenta (TRIM) in the Brillouin zone enclosed by Fermi surfaces is closely linked to the topological class of time-reversal-invariant systems, and can experimentally be investigated. We report here a detailed study of de Haas van Alphen quantum oscillations in single crystals of the topological semimetal CaSn3 with torque magnetometry in high magnetic fields up to 35 T. In conjunction with density functional theory based calculations, the observed quantum oscillations frequencies indicate that the Fermi surfaces of CaSn3 enclose an odd number of TRIM, satisfying one of the proposed criteria to realize topological superconductivity. Nonzero Berry phases extracted from the magnetic oscillations also support the nontrivial topological nature of CaSn3.

Nematic superconductivity in the topological semimetal CaSn3

“…This odd-parity state with a fully opened gap satisfies one of the key prerequisites for topological superconductivity in centrosymmetric time-reversal-invariant systems [2]. Along with the odd number of TRIM enclosed by the Fermi surfaces previously reported [24], CaSn 3 turns out to be a promising candidate material to exhibit topological superconductivity.…”

“…On introducing SOC, the nodal lines evolve into topological point nodes. The nontrivial Berry phase associated with the topological nature of CaSn 3 is experimentally confirmed by recent quantum oscillation measurements [23,24]. Moreover, the Fermi surfaces determined by such measurements are shown to enclose an odd number of TRIM [24], thus fulfilling one of the two prerequisites for topological superconductivity.…”

“…The nontrivial Berry phase associated with the topological nature of CaSn 3 is experimentally confirmed by recent quantum oscillation measurements [23,24]. Moreover, the Fermi surfaces determined by such measurements are shown to enclose an odd number of TRIM [24], thus fulfilling one of the two prerequisites for topological superconductivity. Clearly, it is essential to investigate whether CaSn 3 satisfies also the other prerequisite associated with the superconducting pairing states, namely, if it shows odd-parity pairing.…”

“…Second, we find a mismatch between the carrier densities in the superconductingn s and in the normal state n n of CaSn 3 . Our recent de Haas-van Alphen (dHvA) measurements provide an effective mass m * = 0.18m e and a carrier density n n = 9.3 × 10 20 cm −3 for the predominant hole band located at the point [24]. On the other hand, utilizing λ 0 = m * /μ 0 n s e 2 , we obtain n s 0.06 × 10 20 cm −3 , far below the reported n n value.…”

Photoemission Spectroscopic Evidence of Multiple Dirac Cones in Superconducting BaSn3

“…Recently, superconducting compounds ASn 3 (A=Ca or Ba) were predicted to host topological semimetal states [58][59][60][61][62] . Studies on the topology in the weak coupling superconductor CaSn 3 propose that it hosts topological nodal-line semimetal states in the absent of spin-orbital coupling (SOC) and would evolve to Weyl nodes with SOC [58][59][60] . While, its relatively complicated band structure impedes the direct investigation of the nontrivial band topology therein.…”