Scanning tunneling microscopy studies of the cuprate superconductor HgBa2Ca2Cu3O8+

We report on scanning tunneling microscopy and spectroscopy studies of the slightly underdoped cuprate superconductor HgBa2Ca2Cu3O8+delta, which has an onset Tc approximate to 120 K. Disordered HgO-terminated surfaces were observed after sample cleaving in ultrahigh vacuum, revealing spatially inhomogeneous energy gaps with a low-lying V-shaped structure and the ubiquitous mode features. Similar to Bi-family cuprate superconductors, vortex cores were identified by the suppression of superconducting coherence peaks and the emergence of in -gap features. Superconductivity near step edges is also strongly suppressed over several coherence lengths, forming an effective interface to the superconducting region, where the local spectra show a weak zero -bias conductance peak arising from the Andreev bound states. These results are expected from the widely believed d -wave nature in cuprates, demonstrating a platform for studying unconventional superconductivity.