Scanning Tunneling Microscopy and Spectroscopy of Superconducting FeTe-based Heterostructures

Recently, interface-induced superconductivity has been observed in several FeTe-based heterostructures. FeTe, an antiferromagnetic metal, shares a crystal structure with superconducting FeSe. In this work, we employed molecular beam epitaxy to synthesize a series of FeTe-based heterostructures. In our electrical transport measurements, these FeTe-based heterostructures exhibit superconducting critical temperatures T_c ~11 K. By performing in situ scanning tunneling microscopy and spectroscopy (STM/S), we observed U-shape superconducting gaps with sizes ranging from 2.0 to 4.0 meV. Moreover, we performed spin-polarized STM measurements to probe the evolution of the bicollinear antiferromagnetic order on the top surface of the bottom FeTe layer. We found that the suppression of the bicollinear antiferromagnetic order in FeTe corresponds to the emergence of the superconductivity in FeTe-based heterostructures.