Annual Academic Conference of Dept Physics Fudan University

Annual Academic Conference of Dept. Physics, Fudan University (2016) Nodeless superconducting gaps in noncentrosymmetric superconductor Pb. Ta. Se 2 with topological bulk nodal lines M. X. Wang, 1 Y. Xu, 1 L. P. He, 1 J. Zhang, 1 X. C. Hong, 1 P. L. Cai, 1 Z. B. Wang, 1 J. K. Dong, 1 and S. Y. Li 1, 2, * 1 State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, People’s Republic of China 2 Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433, People’s Republic of China Introduction Recently, the layered, noncentrosymmetric compound Pb. Ta. Se 2 with heavy elements was found to be superconducting [1]. For such a noncentrosymmetric superconductor, there may exist nodes in the superconducting gap if the spin-triplet pairing state plays a significant role. More interestingly, a stable topological nodal-line semimetal state was observed in the normal state of Pb. Ta. Se 2 by angle-resolved photoemission spectroscopy (ARPES) measurements [2]. For superconducting Pb. Ta. Se 2 with such topological band structure, more experiments are highly desired to determine whether it is a topological superconductor. Here we present thermal conductivity measurements of the Pb. Ta. Se 2 single crystal down to 80 m. K to study the superconducting gap structure. ARPES mapping and band calculation of Pb. Ta. Se 2 [2] the noncentrosymmetric crystal structure and superconducting transition of Pb. Ta. Se 2 [1] XRD, optical image, magnetization and resistivity Topological-nodal rings and associated surface states of Pb. Ta. Se 2 [2] Thermal transport properties No residual linear term 0/T : nodeless gap Negligible spin-triplet contribution XRD and dc magnetization measurements show high quality of the Pb. Ta. Se 2 single crystal. Upper critical field HC 2 = 0. 22 T Significant magnetoresistance at 0. 3 K Conclusions ØMultiple nodeless superconducting gaps are demonstrated in the NSC Pb. Ta. Se 2. ØSpin-triplet pairing state is negligible for this NSC. ØThe bulk nodeless gap meets the basic requirement of a topological superconductor. The curve of the normalized 0(H)/T for Pb. Ta. Se 2 is close to that of the multiband s-wave superconductor Nb. Se 2. References [1] Mazhar N. Ali, R. J. Cava, et al. , Phys. Rev. B 89, 020505(R) (2014) [2] G. Bian, M. Z. Hasan, et al. , ar. Xiv: 1505. 03069 M. X. Wang et al. , Phys. Rev. B 93, 020503(R) (2016).