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Yunbo Ou1 Debaleena Nandi3 Katie Huang3 Cigdem Ozsoy-Keskinbora4 Stephan Kraemer5 David Bell4 Philip Kim3 Amir Yacoby3 Jagadeesh Moodera1 2

1, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
3, Harvard University, Cambridge, Massachusetts, United States
4, Harvard University, Cambridge, Massachusetts, United States
5, Harvard University, Cambridge, Massachusetts, United States
2, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States

LaPtBi is a Half-Heusler compound which is recently predicted to exhibit multi-functionalities: the superconductivity and topological edge states, namely topological superconductor. [1, 2] LaPtBi has been shown to superconduct in the bulk. [3] However, and importantly, its topological property can only be stimulated by applying substantial uniaxial strain. In this talk, we report the observation of superconductivity in MBE grown epitaxial non-centrosymmetric LaPtBi film on MgO (001). Transport measurement shows Tc(onset) at 0.7 K and an upper critical field (Bc2 (0)) of 2.1 T. Magnetoresistance in the normal state exhibits a cusp-like minima at low magnetic fields which only depends on the total magnetic field. This is attributed to a weak anti-localization effect arising from the nanocrystalline structure of the film. Linear dependence of the critical magnetic field on temperature down to 50 mK, a non BCS like behavior, is observed. The critical current decreases linearly with magnetic field as well. The I-V characteristics indicate the presence of intrinsic Josephson effect in these nanocrystalline structured films. By optimizing the growth parameters, a compressive uniaxial strain of 17% was introduced into the film. In such a strained LaPtBi film, the predicted topological non-trivial gap at G point is expected to emerge. Characterization of these strained films, including ARPES, will be presented. The realization of superconducting phase in the strained LaPtBi films is an important step towards obtaining a topological superconductor in order to seek other predicted exotic properties such as Majorana states.
Work at MIT is supported by STC Center for Integrated Quantum Materials under NSF Grant No. DMR-1231319, NSF Grant DMR-1700137 and ONR Grant N00014-16-1- 2657
Reference:
[1] D. Xiao et al., Phys. Rev. Lett. 105, 25–28 (2010).
[2] T. Graf et al., Prog. Solid State Chem. 39, 1–50 (2011).
[3] G. Goll et al., Physica B. 403, 1065–1067 (2008).

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