Dresden 2026 – scientific programme

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O: Fachverband Oberflächenphysik

O 17: Spins on surfaces at the atomic scale – Poster

O 17.6: Poster

Monday, March 9, 2026, 18:00–20:00, P2

Spectra and competing correlations in coupled magnetic impurities on superconducting substrates — •Carlos Quesada Pérez and David Jacob — Departamento de Física, Universidad de Alicante, Spain

The study of magnetic impurities in superconductors is a fundamental challenge in condensed matter physics, crucial for understanding phenomena like in-gap states such as Yu-Shiba-Rusinov (YSR) states. Systems with multiple impurities can potentially host exotic ground states relevant for topological quantum applications. Accurate numerical methods like the numerical renormalization group are computationally too demanding for solving more than two impurity levels. Recently, an efficient impurity solver was proposed, based on the exact diagonalization of a single impurity connected to discretized superconducting reservoirs [1]. In this work, we extend this model to the case of two magnetic impurities coupled to BCS superconductors. By exact diagonalization of the resulting tight-binding Hamiltonian, we study the competition between the impurity-superconductor coupling and the impurity-impurity exchange to form a singlet with the bath or a singlet between the impurities themselves. The results reveal the evolution of YSR states and spin correlations, showing transitions between distinct quantum phases driven by this competition.

References:
[1] Phys. Rev. B 108, L220506 (2023)

Keywords: Superconducters; Magnetic impurities; YSR-states; Spin correlations