Full superconducting gap in the doped topological crystalline insulator Sn0.6In0.4Te

Abstract

The thermal conductivity of the doped topological crystalline insulator, Sn0.6In0.4Te superconducting single crystal with Tc = 4.1 K, was measured down to 50 mK. It is found that the residual linear term κ0/T is negligible in zero magnetic field. The κ0/T shows a slow field dependence at low magnetic field. These results suggest that the superconducting gap is nodeless, unless there exist point nodes with directions perpendicular to the heat current. Due to its high-symmetry fcc crystal structure of Sn0.6In0.4Te, however, such point nodes can be excluded. Therefore we demonstrate that this topological superconductor candidate has a full superconducting gap in the bulk. It is likely the unconventional odd-parity A1u state which supports a surface Andreev bound state.

Spin-singlet superconductivity in the doped topological crystalline insulator Sn0.96In0.04Te

“…In a superconductor with nodes, λ is proportional to T n (n 1) at low temperatures. Our result is consistent with the specific heat [17], thermal conductivity [18], and μSR [19] measurements in Sn 1−x In x Te and the scanning tunneling spectroscopy in (Pb 0.5 Sn 0.5 ) 0.7 In 0.3 Te [25]. Figure 5 shows the temperature dependence of the Knight shift K, which is T independent above T c but decreases below T c .…”

“…Point-contact spectroscopy performed on clean single crystals of Sn 0.955 In 0.045 Te found a zero-bias conductance peak, which was taken as a signature of unconventional superconductivity [16]. Specific heat [17], thermal conductivity [18], and μSR [19] have revealed a fully opened superconductiviting gap. Combining these results, a fully gapped pseudo-spin-triplet state was theoretically proposed [20].…”

Indium Substitution Effect on the Topological Crystalline Insulator Family (Pb1−xSnx)1−yInyTe: Topological and Superconducting Properties

“…Later studies on the optimally-doped TCI system SIT using thermal conductivity [67], magnetization, and muon-spin rotation (µSR) measurements [68] also supported the conclusion that SIT has a full superconducting gap in the bulk, and is more likely to be a conventional s-wave superconductor. Similarly, STM measurements [39] of the superconducting state as well as the superconducting energy gap in (Pb 0.5 Sn 0.5 ) 0.7 In 0.3 Te on the high-symmetry (001) surface lead to the same conclusion-that the superconducting sample seems to be fully gapped without any in-gap states-contrary to the expectations for a topological superconductor.…”

Fully gapped superconductivity in In-doped topological crystalline insulatorPb0.5Sn0.5Te

“…ZBCP have been detected by point contact measurements in Sn 1−x In x Te and are also interpreted as signatures of nontrivial topological superconductivity 32 . However, some groups reported later that their data do not support the conclusion of a novel superconductor 33,34 . Whether the superconductivity in doped TCI is topologically nontrivial is still unknown.…”

“…Another interesting result on Cu x Bi 2 Se 3 shows that the zero bias peaks observed in point contact experiments depend on the barrier transparency and they may not represent the intrinsic feature of the compound 16 . Although Sn 1−x In x Te is a candidate of TSC according to theory 32 , a recent thermal conductivity measurement proves that this compound has a full superconducting gap in the bulk 33 . Another group studied Sn 1−x In x Te (x = 0.38 ∼ 0.45) using muon-spin spectroscopy, and the results can be well described by a single-gap s-wave BCS model 34 .…”