Signature of magnetoelectric coupling driven finite momentum pairing in 3D ising superconductor
Fazhi Yang, Heda Zhang, Saswata Mandal, Fanbo Meng, G. Fabbris, Ayman Said, P. M. Lozano, Anil Rajapitamahuni, E. Vescovo, C. S. Nelson, Shan Lin, Y Park, Eleanor M. Clements, Thomas Z. Ward, Ho Nyung Lee, Hechang Lei, Chao‐Xing Liu, Hu Miao
Abstract
The finite momentum superconducting paring states (FMPs) represent a forefront of condensed matter physics. Here we report experimental evidence of FMP in a locally noncentrosymmetric bulk superconductor 4Hb-TaS2. Using hard X-ray diffraction and angle-resolved photoemission spectroscopy, we reveal unusual 2D ferro-rotational charge density wave (CDW) and weak interlayer hopping in 4Hb-TaS2. The superconducting upper critical field, Hc2, linearly increases via decreasing temperature, and well exceeds the Pauli limit, suggesting the dominant orbital pair-breaking mechanism. Remarkably, we observed evidence of field-induced superconductivity-to-superconductivity transition that breaks continuous rotational symmetry of the s-wave uniform pairing in the Bardeen-Cooper-Schrieffer theory down to the six-fold rotation symmetry. Ginzburg-Landau free energy analysis shows that magnetoelectric coupling, induced by 2D ferro-rotational CDW, stabilizes FMP that provides an explanation of the lowering rotation symmetry. Our results provide a new understanding of unconventional superconducting behaviors of the bulk quantum heterostructure 4Hb-TaS2. Finite momentum superconducting pairing refers to a class of unconventional superconducting states where Cooper pairs acquire a non-zero momentum. Here the authors report a new superconducting state in bulk 4Hb-TaS₂, where magnetic fields induce finite momentum pairing via magnetoelectric coupling.