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O: Fachverband Oberflächenphysik

O 52: Focus Session: Spins on Surfaces studied by Atomic Scale Spectroscopies V

O 52.1: Topical Talk

Wednesday, March 20, 2024, 15:00–15:30, MA 004

Locally driven quantum phase transitions in a strongly correlated molecular monolayer — •Markus Ternes — Institute of Physics IIB, RWTH Aachen University, 52074 Aachen, Germany — 2 Peter-Grünberg-Institute (PGI 3), Research Center Jülich, 52425 Jülich, Germany — Jülich Aachen Research Alliance, 52425 Jülich, Germany

The Kondo effect, which appears as a strong zero-bias anomaly, is prototypical for strongly correlated states and therefore cannot be described by single-particle models. Its subtle interplay with magnetically ordered ground states in multi-site Kondo systems continues to attract interest. Here we report on a molecular system of NTCDA molecules on Ag(111) in which individual molecules do not show a Kondo effect even at temperatures of 1K because the π symmetry of their singly occupied orbital hybridizes only weakly with the electrons of the host Ag. In a perfectly ordered lattice, however, newly formed orbital superpositions dramatically increase the hybridization, so that the NTCDA molecules now form a Kondo lattice. Using the electric field exerted by the tip of an STM, we manipulate the orbital superpositions and drive the system through a cascade of quantum phase transitions in which the molecular building blocks change one by one from a Kondo screened to a new paramagnetic ground state, allowing us to reconstruct their complex interactions in detail.

Keywords: Kondo lattices; quantum phase transitions; molecular Kondo effect