Interaction-driven quantum phase transition of a single magnetic impurity in Fe(Se,Te)

• DOI: 10.48550/arxiv.2310.06030
• Publication Date: 2023-01-01
• Authors: Mateo Uldemolins; Andrej Mesaroš; Genda Gu; Alexandra Palacio...; M. Aprili; Pascal Simon; Freek Massee
• Keywords: Quantum phases; Magnetic impurity

Understanding the interplay between individual magnetic impurities and superconductivity is crucial for bottom-up construction of novel phases matter. For decades, description by Yu, Shiba Rusinov (YSR) single spins in a superconductor its extension to include quantum effects has proven highly successful: pair-breaking potential spin generates sub-gap electron- hole excitations that are energetically equidistant from zero. By tuning energy states through zero, impurity screening makes ground state gain or lose an electron, signalling parity breaking phase transition. Here we show multi-orbital impurities, correlations in-gap can conversely lead transition where more than one electron simultaneously leave without significant effect superconductor, while may remain unchanged. This finding implies YSR treatment not always valid, intra-atomic interactions, particularly Hund's coupling favours high configurations, essential ingredient understanding states. The interaction-driven should be taken into account impurity-based band-structure engineering, provide fruitful basis search physics.