1. Annual Academic Conference of Dept. Physics, Fudan University (2016)
Nodeless superconducting gaps in noncentrosymmetric superconductor
PbTaSe2 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. Li1,2,*
1State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai , People’s Republic of China
2Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai , People’s Republic of China
Introduction
Recently, the layered, noncentrosymmetric compound PbTaSe2 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 PbTaSe2 by angle-resolved photoemission spectroscopy (ARPES) measurements [2]. For superconducting PbTaSe2 with such topological band structure, more experiments are highly desired to determine whether it is a topological superconductor. Here we present the thermal conductivity measurements of the PbTaSe2 single crystal down to 80 mK to study the superconducting gap structure.
ARPES mapping and band calculation of PbTaSe2 [2]
Topological-nodal rings and associated surface states of PbTaSe2 [2]
the noncentrosymmetric crystal structure
and superconducting transition of PbTaSe2 [1]
XRD, optical image, magnetization and resistivity
Thermal transport properties
No residual linear term 0/T : nodeless gap
Negligible spin-triplet contribution
The curve of the normalized 0(H)/T
for PbTaSe2 is close to that of the multiband s-wave superconductor NbSe2.
XRD and dc magnetization measurements show high quality of the PbTaSe2 single crystal.
Upper critical field HC2 = 0.22 T
Significant magnetoresistance at 0.3 K
Multiple nodeless superconducting gaps are demonstrated in the NSC PbTaSe2.
Spin-triplet pairing state is negligible for this NSC.
The bulk nodeless gap meets the basic requirement of a topological superconductor.
References
Conclusions
[1] Mazhar N. Ali, R. J. Cava, et al., Phys. Rev. B 89, (R) (2014)
[2] G. Bian, M. Z. Hasan, et al., arXiv:
M. X. Wang et al., Phys. Rev. B 93, (R) (2016).