Broken Time-Reversal Symmetry in Superconducting Partially Filled Skutterudite Pr$_{1-\delta}$Pt$_{4}$Ge$_{12}$
Jia-Wei Zang1, Jian Zhang1,2, Zi-Hao Zhu1, Zhao-Feng Ding1, Kevin Huang1, Xiao-Ran Peng1, Adrian D. Hillier3, Lei Shu1,4**
1State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433 2Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305, USA 3ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Chilton, Didcot, Oxon OX11 0QX, United Kingdom 4Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093
Abstract：Time reversal symmetry (TRS) is a key symmetry for classification of unconventional superconductors, and the violation of TRS often results in a wealth of novel properties. Here we report the synthesis and superconducting properties of the partially filled skutterudite Pr$_{1-\delta}$Pt$_{4}$Ge$_{12}$. The results from x-ray diffraction and magnetization measurements show that the [Pt$_{4}$Ge$_{12}$] cage-forming structure survives and bulk superconductivity is preserved below the superconducting transition temperature $T_{\rm c}=7.80$ K. The temperature dependence of both the upper critical field and the electronic specific heat can be described in terms of a two-gap model, providing strong evidence of multi-band superconductivity. TRS breaking is observed using zero field muon-spin relaxation experiments, and the magnitude of the spontaneous field is nearly half of that in PrPt$_{4}$Ge$_{12}$.
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2019, Vol. 36 
