Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 6: Focus Session Many-Body Phenomena in Nanomagnets: Kondo, Spinons, Spinarons and Beyond (joint session O/TT)

Monday, March 17, 2025, 15:00–18:15, H24

The electron spin, a fundamental quantum mechanical property, plays a crucial role in determining the electronic and magnetic properties as well as the dynamics of matter. Its role becomes even more important at surfaces, 2D materials and nanomagnets as the low-dimensionality increases electron correlation. A fundamental understanding of spin excitations is significant for both fundamental science and modern applications. For decades, the interpretation of experimental signatures of spin excitations were focused on the Kondo effect paradigm, with Co atoms on the (111) surface of noble metals as the prototypical example. However, recent first-principles predictions and spin-polarized scanning tunnelling spectroscopy in high magnetic fields have demonstrated the existence of many-body states, called spinarons. These states arise from the binding of electronic states to spin excitations in the presence of spin-orbit coupling. Such findings, along with other studies, challenge the Kondo interpretation. Furthermore, related non-trivial many-body states may emerge in thin-film geometries, as shown by photoemission spectroscopy and first-principles manybody investigations or in quantum spin liquids. These examples testify that many-body phenomena are not only critically important for the fundamental understanding of spin excitations, they also impact a wide range of material characteristics, including electronic, magnetic, thermodynamic, and transport properties. This focus session will provide a forum to discuss intriguing many-body states driven by spin excitations, and serve as a forum to discuss the current knowledge on their origins, unique properties, and implications.

Organized by
Matthias Bode (Würzburg University), Yujeong Bae (Swiss EMPA), and Stefan Blügel (FZ-Jülich).

	15:00	TT 6.1	Invited Talk: Kondo and Yu-Shiba-Rusinov resonances: transport and coupling — •Laëtitia Farinacci, Gelavizh Ahmadi, Gaël Reecht, Benjamin W. Heinrich, Contanstin Czekelius, Felix von Oppen, and Katharina J. Franke
	15:30	TT 6.2	Invited Talk: Electron delocalization in a 2D Mott insulator — •Amadeo L. Vazquez de Parga, Cosme G. Ayani, Michele Pisarra, Iván M. Ibarburu, Clara Rebanal, Manuela Garnica, Fabián Calleja, and Fernando Martín
	16:00	TT 6.3	Invited Talk: Kondo or no Kondo, that is the question — •Alexander Weismann, Neda Noei, Niklas Ide, and Richard Berndt
	16:30	TT 6.4	Invited Talk: Evidence for spinarons in Co atoms on noble metal (111) surfaces — •Artem Odobesko
	17:00	TT 6.5	Invited Talk: Spinarons: A new view on emerging spin-driven many-body phenomena in nanostructures — •Samir Lounis
	17:30	TT 6.6	Emergence of spinaronic states in Fe adatoms — Ilias Klepetsanis, Juba Bouaziz, •Philipp Rüssman, and Samir Lounis
	17:45	TT 6.7	Revising the Superconductivity in Iron Based Superconductors from the Perspective of Electron Phonon Coupling — •Lanlin Du and Sheng Meng
	18:00	TT 6.8	Theoretical model for multiorbital Kondo screening in strongly correlated molecules with several unpaired electrons — •Manish Kumar, Aitor Calvo-Fernandez, Diego Solar-Polo, Asier Eiguren, Maria Blanco-Rey, and Pavel Jelinek