Atomic scale studies of quantum materials with millikelvin STM

Universidad Autónoma de Madrid

Millikelvin STM provides the tunneling density of states at atomic scale and with a large resolution in energy. This allows studying low energy phenomena, as the physics of heavy fermions, and accessing features that are usually not addressed in STM, as the measurement of the Josephson current between a superconducting tip and a sample. Here I will report on measurements providing new insight into relevant aspects of the CDW in UTe2 [1]. I will also review atomic scale studies at surfaces of quantum materials, including the observation of quantized states of heavy fermion quasiparticles [2], and present recent developments in Josephson Scanning Tunneling Microscopy [3].

[1] Surface charge density wave in UTe2, P. García Talavera et al, Arxiv 2504.12505.
[2] Quantum well states at the surface of a heavy fermion superconductor, E. Herrera et al, Nature 616, 465 (2023).
[3] The feedback driven atomic scale Josephson microscope, S.D. Escribano et al, Nat Com (2025).