Speaker: Herman Suderow (Universidad Autónoma de Madrid)

Host: Paul Canfield

Title: Two dimensional correlated electron physics studied by scanning tunneling spectroscopy at very low temperatures

Abstract: Scanning tunneling microscopy and spectroscopy (STM) at millikelvin temperatures is an interesting technique to study the electronic properties of solids. It is mostly a surface probe, but, as other surface probes, it sometimes directly addresses properties of the bulk. STM has been very useful to better understand electron correlation phenomena, in superconductors, heavy fermions, semimetals or in magnets. STM provides the electronic density of states as a function of energy with a nearly unequaled resolution, allows measuring the band structure by studying Friedel like oscillations close to defects, studying in real space charge density waves, or observing the superconducting vortex lattice. In a few recent examples, we have observed correlated electron physics at the surface, probably unveiling novel two-dimensional systems. On the surface of the heavy fermion URu2Si2 we observe quantized heavy fermion states [1]. In a pnictide superconductor, we observe two-dimensional high Tc superconductivity. These results raise the question of how two-dimensional electronic correlated behavior can help better understanding the bulk and predicting new bulk properties.

[1] Quantum-well states at the surface of a heavy-fermion superconductor, E. Herrera et al, Nature 616, 465–469 (2023)