講演情報
[8p-E207-15]Rotational-symmetry-breaking superconductivity in α-Sn thin films grown on GaAs(001) substrates
〇Shingen Miura1, Hirotaka Hara1, Tomoki Hotta1, Hideki Maki1, Duc Anh Le1,2, Masaaki Tanaka1,2 (1.Univ. of Tokyo, 2.CSRN, Univ. of Tokyo)
キーワード：
superconductivity
Superconductivity in a topological Dirac semimetal (TDS) can inherit the band topology of the normal state, imprinting it onto the Cooper-pair condensate. Group-theoretical analysis predicts two-component odd-parity pairing channels, whose order parameter may spontaneously break the in-plane rotational symmetry, producing a twofold anisotropy in the in-plane upper critical field locked to a crystallographic axis. Although similar behavior has been reported in doped topological insulators, whether it occurs in compressively strained α-Sn, a three-dimensional TDS, has remained open.We grew 20 nm-thick α-Sn films by molecular beam epitaxy on GaAs(001) with InSb (tInSb = 15–250 nm)/AlSb/AlAs/GaAs buffer layers, and investigated transport under in-plane magnetic fields along various directions. Films with tInSb = 15 and 50 nm exhibit superconductivity with Tc = 4.0 K, slightly above bulk β-Sn (3.72 K). Below Tc, the resistance shows a twofold angular dependence on the in-plane field direction, with the largest Hc2 along GaAs [-110]. This anisotropy is unchanged between Hall bars along [110] and [-110], indicating independence from the current direction. The normal-state resistance is isotropic, demonstrating that the anisotropy is intrinsic to the superconducting phase. The anisotropy ratio γ is largest just below Tc and decreases toward unity at lower temperatures, consistent with strain-pinned two-component order parameters. This work suggests that superconducting α-Sn is a promising platform for nematic superconductivity.