Scanning tunneling microscopy and spectroscopy have become indispensable tools for probing condensed matter at atomic length scales, yet achieving ultimate energy resolution remains a persistent challenge. At mK temperatures, the dynamical Coulomb blockade regime fundamentally limits spectroscopic precision through energy exchange between tunneling electrons and the electromagnetic environment. Here, we demonstrate that combining local electromagnetic shielding with low-pass filtering directly at the cryogenic scan head improves the energy resolution by nearly an order of magnitude, reaching benchmark values as low as 3.7μeV at 10mK. We attribute this enhancement to efficient suppression of high-frequency radiation and capacitive shunting of the tunnel junction. Remarkably, this improved sensitivity reveals that the Josephson current couples to electromagnetic cavity modes of the centimeter-scale scan head, establishing a direct connection between atomic-scale tunneling processes and macroscopic cavity quantum electrodynamics. These advances open pathways for exploring ultra-low-energy phenomena with unprecedented precision.
@article{arxiv.2603.03166,
title = {Enhancing the Energy Resolution in Scanning Tunneling Microscopy: from dynamical Coulomb blockade to cavity quantum electrodynamics},
author = {Xianzhe Zeng and Janis Siebrecht and Haonan Huang and Sujoy Karan and Joachim Ankerhold and Klaus Kern and Christian R. Ast},
journal= {arXiv preprint arXiv:2603.03166},
year = {2026}
}
Comments
11 pages, 5 figures, including supporting information