Superconductivity in rubidium - substituted

We report on the synthesis and the physical properties of Ba1−xRbxTi2Sb2O (x ≤ 0.4) by x-ray diffraction, superconducting quantum interference device magnetometry, resistivity, and specificheat measurements. Upon hole doping by substituting Ba with Rb, we find superconductivity with a maximum Tc=5.4 K. Simultaneously, the charge-density-wave transition temperature is strongly reduced from TCDW�55 K in the parent compound BaTi2Sb2O and seems to be suppressed for x�0.2. The bulk character of the superconducting state for the optimally doped sample (x=0.2) is confirmed by the occurrence of a well developed discontinuity in the specific heat at Tc, with ΔC/Tc�22 mJ/mol K2, as well as a large Meissner-shielding fraction of �40%. The isotropically averaged lower and upper critical fields of the optimally doped sample (x=0.2) are estimated to �0Hc,1(0)�3.8 mT and �0Hc,2(0)�2.3 T, respectively, indicating that these compounds are strongly type-II superconductors. DOI: https://doi.org/10.1103/PhysRevB.89.094505 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-106879 Originally published at: von Rohr, Fabian; Nesper, Reinhard; Schilling, Andreas (2014). Superconductivity in rubidium-substituted Ba1−xRbxTi2Sb2O. Physical Review B, 89(094505):online. DOI: https://doi.org/10.1103/PhysRevB.89.094505 Superconductivity in rubidium substituted Ba1-xRbxTi2Sb2O Fabian von Rohr, 2, ∗ Reinhard Nesper, and Andreas Schilling Physik-Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland Laboratory of Inorganic Chemistry, ETH Zürich, Wolfgang-Pauli-Str. 10, CH-8093 Zürich, Switzerland (Dated: November 7, 2013) Abstract We report on the synthesis and the physical properties of Ba1-xRbxTi2Sb2O (x ≤ 0.4) by x-ray diffraction, SQUID magnetometry, resistivity and specific heat measurements. Upon hole doping by substituting Ba with Rb, we find superconductivity with a maximum Tc = 5.4 K. Simultaneously, the charge-density-wave (CDW) transition temperature is strongly reduced from TCDW ≈ 55 K in the parent compound BaTi2Sb2O and seems to be suppressed for x ≥ 0.2. The bulk character of the superconducting state for the optimally doped sample (x = 0.2) is confirmed by the occurrence of a well developed discontinuity in the specific heat at Tc, with ∆C/Tc ≈ 22 mJ/mol K2, as well as a large Meissner-shielding fraction of ≈ 40 %. The lower and the upper critical fields of the optimally doped sample (x = 0.2) are estimated to μ0Hc,1(0) ≈ 3.8 mT and μ0Hc,2(0) ≈ 2.3 T, respectively, indicating that these compounds are strongly type-II superconductors. 1 ar X iv :1 31 1. 14 93 v1 [ co nd -m at .s up rco n] 6 N ov 2 01 3