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Time-reversal invariant and fully gapped unconventional superconducting state in the bulk of the topological compound Nb0.25Bi2Se3

Journal Article · · Physical Review B
 [1];  [2];  [3];  [1];  [2];  [4];  [5];  [6];  [5];  [1];  [1];  [1]
  1. Paul Scherrer Inst. (PSI), Villigen (Switzerland)
  2. Okayama Univ. (Japan)
  3. Hofstra University, Hempstead, NY (United States)
  4. Karlsruhe Inst. of Technology (KIT) (Germany)
  5. Princeton Univ., NJ (United States)
  6. Argonne National Lab. (ANL), Lemont, IL (United States)
+ Show Author Affiliations
Recently, the niobium (Nb) doped topological insulator Bi2Se3, in which the finite magnetic moments of the Nb atoms are intercalated in the van der Waals gap between the Bi2Se3 layers, has been shown to exhibit both superconductivity with $$T_c$$ ≃ 3 K and topological surface states. Here we report on muon spin rotation experiments probing the temperature and field dependence of effective magnetic penetration depth $$λ_{\text{eff}}(T)$$ in the layered topological superconductor candidate Nb0.25Bi2Se3. In this work the exponential temperature dependence of $$λ^{–2}_{\text{eff}}(T)$$ at low temperatures suggests a fully gapped superconducting state in the bulk with the superconducting transition temperature $$T_c$$ = 2.9 K and the gap to $$T_c$$ ratio 2Δ /$$k_BT_c$$ = 3.95(19). We also reveal that the ratio Tc/λ–2eff is comparable to those of unconventional superconductors, which hints at an unconventional pairing mechanism. Furthermore, time-reversal symmetry breaking was excluded in the superconducting state with sensitive zero-field μSR experiments. We hope the present results will stimulate theoretical investigations to obtain a microscopic understanding of the relation between superconductivity and the topologically nontrivial electronic structure of Nb0.25Bi2Se3.
Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States)
Sponsoring Organization:
Japan Society for the Promotion of Science (JSPS); USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
Grant/Contract Number:
AC02-06CH11357
OSTI ID:
1765365
Journal Information:
Physical Review B, Journal Name: Physical Review B Journal Issue: 13 Vol. 102; ISSN 2469-9950
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY