Séminaire LPEM : Beilun WU, Universidad Autónoma de Madrid, Spain

Scanning Tunneling Microscopy at high magnetic fields

By Beilun WU

Laboratorio de Bajas Temperaturas y Altos Campos Magnéticos, Departamento de Física de la Materia Condensada, Instituto Nicolás Cabrera and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain

In this talk, I will discuss recent advances in our scanning tunneling microscopy and spectroscopy experiment at magnetic fields of 22 T. First, I will present improvements in the instrumentation that have allowed to build compact microscopes with which we have been able to make measurements up to 20 T. I will then discuss results obtained in iron pnictide superconductors. I will focus on the recent family of CaKFe4As4 materials, which have very high critical temperatures (up to 38 K) and present isotropic two gap superconductivity. I will show measurements of the properties of the vortex lattice and of the band structure, the latter obtained using quasiparticle interference. I will further present recent results on the vortex phase and the band structure of other iron pnictide superconductors.