With the recent discovery of the quantum anomalous Hall insulator (QAHI), which exhibits the conductive quantum Hall edge states without external magnetic field, it becomes possible to create a novel topological superconductor by introducing superconductivity into these edge states. In this case, two distinct topological superconducting phases with one or two chiral Majorana edge modes were theoretically predicted, characterized by Chern numbers (N ) of 1 and 2, respectively. We present spectroscopic evidence from Andreev reflection experiments for the presence of chiral Majorana modes in a Nb / (Cr0.12Bi0.26Sb0.62)2Te3 heterostructure with unique signatures attributed to two different topological superconducting phases. The results are consistent with the theoretical predictions.

Recently, it was pointed out that all chiral crystals with spin-orbit coupling (SOC) can be Kramers Weyl semimetals (KWSs) which possess Weyl points pinned at time-reversal invariant momenta. In this work, we show that all achiral non-centrosymmetric materials with SOC can be a new class of topological materials, which we term Kramers nodal line metals (KNLMs). In KNLMs, there are doubly degenerate lines, which we call Kramers nodal lines (KNLs), connecting time-reversal invariant momenta. The KNLs create two types of Fermi surfaces, namely, the spindle torus type and the octdong type. Interestingly, all the electrons on octdong Fermi surfaces are described by two-dimensional massless Dirac Hamiltonians. These materials support quantized optical conductance in thin films. We further show that KNLMs can be regarded as parent states of KWSs. Therefore, we conclude that all non-centrosymmetric metals with SOC are topological, as they can be either KWSs or KNLMs.

Recently, two multifold fermions materials, AlPt [1] and XSi(X=Rh,Co) [2][3][4], characterized by multifold degeneracy band crossings at time-reversal invariant momenta (TRIMs) have been discovered in chiral crystals experimentally. In this work, we largely expand the family of multifold fermions by pointing out that several well-studied noncentrosymmetric superconductors are indeed multifold fermion metals. Importantly, their normal state topological properties, which have been ignored in previous studies, play an important role in the superconducting properties. Taking Li2Pd3B and Li2Pt3B as examples, we found a large number of unconventional degenerate point, such as double spin-1, spin-3/2, Weyl and double Weyl topological band crossing points near the Fermi energy, which result in finite Chern numbers on Fermi surfaces. Long Fermi arc states in Li2Pd3B, originating from the nontrivial band topology were found. Importantly, it has been shown experimentally that Li2Pd3B and Li2Pt3B are fully gapped and gapless superconductors respectively. By analyzing the possible pairing symmetries, we suggest that Li2Pd3B can be a DIII class topological superconductor with Majorana surface states, even if the spin-orbit coupling in Li2Pd3B is negligible. Interestingly, Li2Pt3B, being gapless, is likely to be a nodal topological superconductor with dispersion-less surface Majorana modes. We further identified that several noncentrosymmetric superconductors, such as Mo3Al2C, PdBiSe, Y2C3 and La2C3, are multifold fermion superconductors whose normal state topological properties have been ignored in previous experimental and theoretical studies.