Scanning tunneling spectroscopy in quantum materials at very low temperatures

DIPC Seminars

Hermann Suderow
Universidad Autonoma de Madrid
Hybrid Seminar: Donostia International Physics Center
Nacho Pascual
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Scanning tunneling spectroscopy in quantum materials at very low temperatures

In this talk, I will review recent advances in Scanning tunneling microscopy and spectroscopy (STM) at mK temperatures in dilution refrigerators, discuss results obtained in heavy fermion materials and mention possible future lines of research. First, I will discuss URu2Si2, a heavy fermion superconductor (Tc=1.5K) hosting a misterious hidden order phase below 17.5 K. Previous STM and angular resolved photoemission (ARPES) results in this system have been helpful to understand the formation of heavy bands and to characterize the opening of a gap in the hidden order phase. More recent results show that this system also hosts two-dimensional heavy fermions (2DHF) at the surface. The 2DHF are made of 5f electrons with an effective mass 17 times the free electron mass and form quantized states at terraces. The energy separation between quantized levels is of a fraction of a meV and the level width is set by the interaction with correlated bulk states. Edge states on steps between terraces suggest electronic in-plane symmetry breaking at the surface. Then, I will present advances in other heavy fermion systems, and finally discuss new improvements in the measurement of the Josephson effect at very low temperatures and how these might help in studying surfaces of topological superconductors.