Spinless pseudospin in space group Pnma: Application to UCoGe*

Spatial inversion and time reversal symmetries ensure that electronic energy bands are doubly degenerate everywhere in momentum space.  Such a Karmers spin degeneracy is usually lifted by external magnetic fields.  We have found an unusual Kramers degeneracy which does not couple to a Zeeman field – we name it spinless pseudospin – and have identified where we can see such fermions [1,2].  In this talk, we discuss a particular example of spinless pseudospin by considering UCoGe, which has an orthorhombic crystal structure and space group Pnma.  Through DFT calculations and symmetry analysis, we show how the effective coupling to a Zeeman field vanishes and discuss implications for superconductivity.  [1] Yue Yu, Tatsuya Shishidou, Shuntaro Sumita, Michael Weinert, Daniel F. Agterberg, arXiv:2310.00838 (2023).  [2] Han Gyeol Suh, Yue Yu, Tatsuya Shishidou, Michael Weinert, P. M. R. Brydon, and Daniel F. Agterberg, Phys. Rev. Research 5, 033204 (2023).