Cologne team sees Andreev states matching theory in topological insulator junctions
Physicists at the University of Cologne, led by Professor Yoichi Ando with Dr Jakob Schluck and Ella Nikodem, studied a Josephson junction built on a topological insulator combined with a superconductor. Using tunneling spectroscopy while varying the phase difference between the two superconductors, they observed highly transmissive Andreev states across a range of charge-carrier densities. Under an applied magnetic field, the states concentrated in specific regions of the junction, and the results agree with the 2008 Liang Fu and Charles Kane model and with simulations by Professor Fabian Hassler's group at RWTH Aachen University. The work was published in Science Advances as "Tunneling spectroscopy of topological insulator Josephson junctions"; the predicted closing and reopening of an energy gap, which could signal a transition to topological superconductivity, has not yet been confirmed.