Superconductivity of (Sn1−z Pbz)1−x InxTe alloys

Parfen’ev, R. V.; Шамшур, Д. В.; Немов, С. А.

doi:10.1134/1.1410620

Cited by 13 publications

(10 citation statements)

References 4 publications

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“…Earlier studies on polycrystalline samples of (Pb 1−z Sn z ) 1−x In x Te investigated the dependence of T c and H c2 in the concentration ranges 0.4 z 1 and 0.03 x 0.2 [19][20][21]. The maximum T c was found for z = 0.5; however, the solubility limit in these polycrystalline samples was reached by x ∼ 0.2.…”

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confidence: 98%

Superconductivity induced by In substitution into the topological crystalline insulator Pb0.5 Sn0.5Te

et al. 2014

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Indium substitution turns the topological crystalline insulator (TCI) Pb 0.5 Sn 0.5 Te into a possible topological superconductor. To investigate the effect of the indium concentration on the crystal structure and superconducting properties of (Pb 0.5 Sn 0.5 ) 1−x In x Te, we have grown high-quality single crystals using a modified floating-zone method and have performed systematic studies for indium content in the range 0 x 0.35. We find that the single crystals retain the rocksalt structure up to the solubility limit of indium (x ∼ 0.30). Experimental dependencies of the superconducting transition temperature (T c ) and the upper critical magnetic field (H c2 ) on the indium content x have been measured. The maximum T c is determined to be 4.7 K at x = 0.30, with μ 0 H c2 (T = 0) ≈ 5 T.

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confidence: 98%

Superconductivity induced by In substitution into the topological crystalline insulator Pb0.5 Sn0.5Te

et al. 2014

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“…At this Pb concentration the system becomes a TCI 19 . Also, substitution of a small amount of In turns the system into a true bulk insulator 20 , while adding more In makes it superconducting 21,22 . For reference, we note that the proximity of the superconductivity and the suppressed ferroelectric order suggests a possible connection with the enhanced superconductivity at the ferroelectric quantum critical point in SrTiO 3 23,24 .In this Rapid Communication, we use inelastic neutron scattering (INS) to measure the phonon density of states (PDOS) in polycrystalline samples of (Pb 0.5 Sn 0.5 ) 1−x In x Te (PSIT) with x = 0 (a nonsuperconducting TCI), and x = 0.3 (a superconductor with a critical temperature T c of 4.7 K).…”

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confidence: 99%

Unusual phonon density of states and response to the superconducting transition in the In-doped topological crystalline insulator Pb0.5Sn0.5Te

et al. 2018

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We present inelastic neutron scattering results of phonons in (Pb0.5Sn0.5)1−xInxTe powders, with x = 0 and 0.3. The x = 0 sample is a topological crystalline insulator, and the x = 0.3 sample is a superconductor with a bulk superconducting transition temperature Tc of 4.7 K. In both samples, we observe unexpected van Hove singularities in the phonon density of states at energies of 1-2.5 meV, suggestive of local modes. On cooling the superconducting sample through Tc, there is an enhancement of these features for energies below twice the superconducting-gap energy. We further note that the superconductivity in (Pb0.5Sn0.5)1−xInxTe occurs in samples with normal-state resistivities of order 10 mΩ cm, indicative of bad-metal behavior. Calculations based on density functional theory suggest that the superconductivity is easily explainable in terms of electron-phonon coupling; however, they completely miss the low-frequency modes and do not explain the large resistivity. While the bulk superconducting state of (Pb0.5Sn0.5)0.7In0.3Te appears to be driven by phonons, a proper understanding will require ideas beyond simple BCS theory.Topological insulators (TIs) represent an exotic state of matter in which the bulk is insulating but the surface is metallic 1,2 . The topological state is protected by the time-reversal symmetry 1 . By including a certain crystal point group symmetry instead of time reversal, topological crystalline insulators (TCIs), a state analogous to TIs, was also proposed 3,4 . In particular, it was predicted that compounds such as SnTe might be TCIs 5 , and the key features, including the inverted character of bands near the chemical potential 6,7 and surface states within the band gap that are protected from back-scattering 8,9 , were soon verified.These developments have also spurred renewed interest in topological superconductors, as such materials may exhibit gapless surface states that could be beneficial for quantum computing 1-3 . A common aspect of TCIs is strong spin-orbit coupling in the atomic states contributing to the valence and conduction bands, and this is a useful ingredient for obtaining the unusual pairing symmetry expected for a topological superconductor. Hence, there is interest in seeing whether doping TCIs can induce superconductivity with a topological nature. Indeed, one can make SnTe superconducting by introducing In, and a point-contact study found evidence of surface Andreev bound states 10 , though thermodynamic studies suggest a fully gapped superconducting state [11][12][13] .SnTe is a compound that has the rocksalt structure despite the fact that the component elements do not all form closed-shell ions. A consequence is a strong intrinsic electron-phonon coupling 14,15 , which leads to a ferro-electric phase transition in SnTe 16,17 . One way to suppress the ferroelectric transition is to substitute Pb for Sn, and it has been estimated that the transition should hit 0 K for Pb y Sn 1−y Te with y ≈ 0.5 18 . At this Pb concentration the system becomes a TCI 19 . Also, s...

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“…Whether the superconductivity in doped TCI is topologically nontrivial is still unknown. Superconductivity was also found in In doped Pb 1−z Sn z Te [35][36][37][38][39][40][41] , and this material is a new possible candidate for TSC according to former theoretical proposals 32 . The quality of (Pb 1−z Sn z ) 1−x In x Te crystals and the superconducting transition temperature has been improved recently 42 , and T c reaches maximum 4.7 K at its optimum doping of x = 0.3.…”

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

Fang

et al. 2015

Phys. Rev. B

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Superconductors derived from topological insulators and topological crystalline insulators by doping have long been considered to be candidates as topological superconductors. Pb0.5Sn0.5Te is a topological crystalline insulator with mirror symmetry protected surface states on (001), ( 011) and ( 111) oriented surfaces. The superconductor (Pb0.5Sn0.5)0.7In0.3Te is induced by In doping in Pb0.5Sn0.5Te, and is thought to be a topological superconductor. Here we report the first scanning tunneling spectroscopy measurement of the superconducting state as well as the superconducting energy gap in (Pb0.5Sn0.5)0.7In0.3Te on a (001)-oriented surface. The spectrum can be well fitted by an anisotropic s-wave gap function of ∆ = 0.72 + 0.18 cos 4θ meV using Dynes model. The results show that the quasi-particle density of states seem to be fully gapped without any in-gap states, in contradiction with the expectation of a topological superconductor.

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Superconductivity of (Sn1−z Pbz)1−x InxTe alloys

Cited by 13 publications

References 4 publications

Superconductivity induced by In substitution into the topological crystalline insulator Pb0.5 Sn0.5Te

Superconductivity induced by In substitution into the topological crystalline insulator Pb0.5 Sn0.5Te

Unusual phonon density of states and response to the superconducting transition in the In-doped topological crystalline insulator Pb0.5Sn0.5Te

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

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