Evidence of triplet superconductivity in Bi/Ni bilayers: Theoretical analysis of point contact Andreev reflection spectroscopy results

Abstract: A theoretical formalism of Andreev reflection is employed to provide theoretical support for distinguishing between the singlet pairing and the triplet pairing by the point contact Andreev reflection (PCAR) experiments. We utilize our theoretical curves to fit the data of the PCAR experiment on unconventional superconductivity in the Bi/Ni bilayer [arXiv:1810.10403] and find the Anderson-Brinkman-Morel (ABM) state satisfies the main characteristics of the experimental data. The chiral cross-section of the ABM state might explain well the broken time-reversal symmetry determined by the polar Kerr effect measurements and the time-domain THz spectroscopy in Bi/Ni bilayers. Moreover, the Andreev reflection spectra of the Balian-Werthamer state and the chiral $p$-wave state are also presented.