Van der Waals-Zeeman Colloquium
Tuesday, 29 March 2011, 16:00
Scanning tunneling spectroscopy at very low temperatures
Prof. Hermann Suderow
Universidad Autonoma de Madrid
Scanning Tunneling Microscopy and Spectroscopy (STM/S) down to 100mK is an efficient tool to study superconductors and strongly correlated electron systems. The local electronic density of states is obtained at atomic level with a resolution in energy of some tens of micro eV. In this talk, I will review the basics of the technique, including well established methods to measure the local density of states as a function of the position, temperature and magnetic field. I will also discuss measurements of the local density of states of layered transition metal dichalcogenides (MX2 where M=Nb,Ta and X=S,Se), which show particularly well interesting features of their superconducting properties, related to the effect of charge order on superconductivity. While NbSe2 and NbS2 come up as two band superconductors, TaS2 appears as the first system where superconductivity coexists with chiral charge order. On the other hand, STM/S experiments of the vortex lattice give visual account of ubiquitous phenomena in superconductors, such as vortex lattice melting and vortex bundle motion.