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

Abstract

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.

Surface-state-dominated transport in crystals of the topological crystalline insulator In-dopedPb1−xSnxTe

“…This allows one to exploit the unusual properties of the surface states in transport measurements without the need to apply a bias voltage to the surface. There is also strong interest in inducing topological superconductivity at surfaces or interfaces 2 , and we note that there are exciting possibilities to create interfaces between the present topological insulators and superconductors of closely related alloys 20,32 , such as In-doped SnTe and Pb 0.5 Sn 0.5 Te.…”

“…The topological character changes from non-trivial at x = 1 to trivial at x = 0, with a topological quantum phase transition at x c ≈ 0.35, corresponding to the point at which band inversion onsets 8,[17][18][19] . In our previous investigation of indium-induced superconductivity in Pb 0.5 Sn 0.5 Te single crystals 20 , we observed a non-monotonic variation in the normal-state resistivity with indium concentration, with a maximum at 6% indium doping. Further motivation has come from older work 21 on various compositions of (Pb 1−x Sn x ) 1−y In y Te.…”

“…Further motivation has come from older work 21 on various compositions of (Pb 1−x Sn x ) 1−y In y Te. (Note that In doping reduces the lattice parameter 20 , so that, like pressure 16 , it should reduce x c for band inversion.) Hence, we have performed a systematic study, growing and characterizing single crystals with six Pb/Sn ratios (x = 0.2, 0.25, 0.3, 0.35, 0.4, 0.5) and a variety of In concentrations (y = 0-0.2).…”

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

“…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. To verify its topological properties accurately, detecting the gap structure is strongly called for.…”

“…The high-quality single crystal was grown by the floating-zone method 42 . The DC magnetic susceptibility was measured using a commercial Magnetic Property Measurement System (SQUID-VSM, Quantum Design).…”