Structural and electronic inhomogeneity of superconducting Nb-doped Bi2Se3

Simone M. Kevy; Henriette E. Lund; Laura Wollesen; Kirstine J. Dalgaard; Yu-Te Hsu; Steffen Wiedmann; Marco Bianchi; Ann Julie Utne Holt; Davide Curcio; Deepnarayan Biswas; Alfred J. H. Jones; Klara Volckaert; Cephise Cacho; Pavel Dudin; Philip Hofmann; Martin Bremholm

doi:10.1103/PhysRevB.103.085107

Structural and electronic inhomogeneity of superconducting Nb-doped Bi2Se3

Simone M. Kevy, Henriette E. Lund, Laura Wollesen, Kirstine J. Dalgaard, Yu-Te Hsu, Steffen Wiedmann, Marco Bianchi, Ann Julie Utne Holt, Davide Curcio, Deepnarayan Biswas, Alfred J. H. Jones, Klara Volckaert, Cephise Cacho, Pavel Dudin, Philip Hofmann, Martin Bremholm

DOI 10.1103/PhysRevB.103.085107 · Physical Review B

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Abstract

The crystal structure, electronic structure, and transport properties of crystals with the nominal composition Nb0.25Bi2Se3 are investigated. X-ray diffraction reveals that the as-grown crystals display phase segregation and contain major contributions of BiSe and the superconducting misfit layer compound (BiSe)1.1NbSe2. The inhomogeneous character of the samples is also reflected in the electronic structure and transport properties of different single crystals. Angle-resolved photoemission spectroscopy (ARPES) reveals an electronic structure that resembles poor-quality Bi2Se3 with an ill-defined topological surface state. High-quality topological surface states are instead observed when using a highly focused beam size, i.e., nanoARPES. While the superconducting transition temperature is found to vary between 2.5 and 3.5 K, the majority of the bulk single crystals does not exhibit a zero-resistance state suggesting filamentary superconductivity in the materials. Susceptibility measurements of the system together with the temperature dependence of the coherence length extracted from the upper critical field are consistent with conventional BCS superconductivity of a type II superconductor.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Nb0.25Bi2Se3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	3.5	Pressure not reported	onset
Nb0.25Bi2Se3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	2.5	Pressure not reported	zero_resistance
(BiSe)1.1NbSe2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure not reported	unknown