Interest in topological states of matter exploded over a decade ago with the theoretical prediction and experimental detection of three-dimensional topological insulators, especially in bulk materials that can be tuned out of it by doping. However, their superconducting counterpart, the time-reversal invariant three-dimensional topological superconductor, has evaded discovery thus far. In this work, we provide transport evidence that K-doped β-PdBi2 is a 3D time-reversal-invariant topological superconductor. In particular, we find signatures of Majorana surface states protected by time-reversal symmetry--the hallmark of this phase--in soft point-contact spectroscopy, while the bulk system shows signatures of odd-parity pairing via upper-critical field and magnetization measurements. Odd-parity pairing can be argued, using existing knowledge of the band structure of β-PdBi2, to result in 3D topological superconductivity. Moreover, we find that the undoped system is a trivial superconductor. Thus, we discover β-PdBi2 as a unique material that, on doping, can potentially undergo an unprecedented topological quantum phase transition in the superconducting state.
@article{arxiv.1809.08708,
title = {Transport evidence for three dimensional topological superconductivity in doped $\beta$-PdBi$_2$},
author = {Ayo Kolapo and Tingxin Li and Pavan Hosur and John H. Miller},
journal= {arXiv preprint arXiv:1809.08708},
year = {2020}
}