Topological superconductivity in a Bi₂Te₃/NbSe₂ heterostructure: A review

Topological superconductors carry globally protected gapless boundary excitations, which are robust under local perturbations, and thus exhibit both fundamental and applicational importance. An unconventional pairing with p-wave symmetry, such as a nontrivial topology in the superconductor's wavefunction, is required to generate a non-zero Berry phase. Until now, the Bi₂Te₃/2H-NbSe₂ heterostructure has proven to be a practical way to realize a topological superconductor in real materials. This complex system, where odd numbers of spin-momentum locked Dirac cone surface states on the topological insulator Bi₂Te₃ become superconducting, induced by the proximate effect from the underlying s-wave superconductor 2H-NbSe₂, realizes an effective two-dimensional (2D) spinless p_x + i p_y topological superconductor. In this review article, we summarize the recent experimental progress of the successful synthesis of Bi₂Te₃/2H-NbSe₂ heterostructures using molecular beam epitaxy, determining the thickness limit of the heterostructure, detecting the long thought Majorana quasiparticle inside a magnetic vortex core state by means of scanning tunneling microscopy and demonstration of the unique spatial and spin properties of a Majorana zero mode.