Unequivocal identification of spin-triplet superconductors with upper critical field and flux quantization

Chih-Chieh Chiang^1,2*, Hung-Chieh Lee¹, Shi-Chieh Lin³, Danru Qu³, Ming-Wen Chu³, Chii-Dong Chen⁴, C. L. Chien^1,2, Ssu-Yen Huang¹

¹Department of Physics, National Taiwan University, Taipei, Taiwan
²Willian H. Miller III Department of Physics and Astronomy, Johns Hopkins University, Baltimore, USA
³Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
⁴Institute of Physics, Academia Sinica, Taipei, Taiwan

* Presenter:Chih-Chieh Chiang, email:ccchiang112@gmail.com

Superconductors (SCs) with spin-triplet pairings are significant for developing quantum computation and exploring Majorana physics. The pairing state of Cooper pairs can have spin-singlet and spin-triplet, but most known SCs are spin-singlet. In centrosymmetric SCs, the pairing state must be either spin-singlet (even parity) or spin-triplet (odd parity). However, noncentrosymmetric SCs with broken inversion symmetries host a mixture of singlet and triplet states. In this work, we demonstrate two methods – kink-point upper critical field and half-quantum flux can simultaneously detect spin-triplet pairings in centrosymmetric SC β-Bi₂Pd, and noncentrosymmetric SC α-BiPd, but the BCS-like results and integer quantization in centrosymmetric γ-BiPd indicating spin-singlet pairing. The kink-point upper critical field and phase-sensitive measurements are essential for exploring triplet superconductors and their quantum properties. [1]

[1] C. C. Chiang, H. C. Lee, S. C. Lin, D. Qu, M. W. Chu, C. D. Chen, C. L. Chien, and S. Y. Huang, Phys. Rev. Lett. 131, 236003 (2023).

Keywords: Phase-sensitive measurement, Spin-triplet Superconductor, upper critical field