Low-energy excitations and non-BCS superconductivity in Nb\(_x\)-Bi\(_2\)Se\(_3\)

When certain elemental metals like Cu, Sr and Nb are intercalated between the layers of Bi\(_2\)Se\(_3\), a topological insulator, the intercalated systems superconduct with critical temperatures around 3 K. Naturally, in all these cases, the possibility of topological superconductivity was suggeste...

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Bibliographic Details
Published inarXiv.org
Main Authors Sirohi, Anshu, Das, Shekhar, Prakriti Neha, Jat, Karn S, Patnaik, Satyabrata, Sheet, Goutam
Format Paper
LanguageEnglish
Published Ithaca Cornell University Library, arXiv.org 28.06.2018
Subjects
Copper
Niobium
Order parameters
Scanning tunneling microscopy
Spectrum analysis
Superconductivity
Topological superconductors
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Summary:When certain elemental metals like Cu, Sr and Nb are intercalated between the layers of Bi\(_2\)Se\(_3\), a topological insulator, the intercalated systems superconduct with critical temperatures around 3 K. Naturally, in all these cases, the possibility of topological superconductivity was suggested and explored. However, in cases of Cu and Sr intercalated systems, the low-temperature scanning tunneling microscopy (STM) experiments revealed fully formed gaps where no signature of low-energy states, a requisite for topological superconductivity, was found. Here, through STM spectroscopy down to 400 mK we show that in Nb\(_x\)-Bi\(_2\)Se\(_3\) (\(x\) = 0.25), the spectra deviate from a BCS-like behavior and the spectral weight at low-bias is large. Our observations are consistent with the idea that the order parameter of Nb\(_x\)-Bi\(_2\)Se\(_3\) is nodal. Therefore, our results conclude that compared to other members of the family, Nb\(_x\)-Bi\(_2\)Se\(_3\) has a stronger possibility of being a topological superconductor.
ISSN:2331-8422
DOI:10.48550/arxiv.1806.11143