arXiv subjects

Lidia Stocker

Publications and source records attributed to Lidia Stocker.

4 recordsLinked to original sources

arXiv2026

Pathway to Kondo physics in ytterbium atom chains with repulsive spin impurities

The Kondo effect is a paradigmatic model of strongly-correlated physics, where a magnetic impurity forms a many-body singlet with a fermionic environment. Cold gases of ytterbium (Yb) atoms have been proposed to be an ideal platform to study the Kondo effect since different internal states of the atom can be used to create both the impurity and the fermionic environment. In Yb gases, however, the atomic impurity interacts with the fermionic environment both through magnetic and potential scattering. These two scattering mechanisms counteract one another, raising the question of how robust Kondo screening remains. Here, we show that potential scattering can quench the Kondo screening in one-dimensional Yb gases; yet, strikingly, Kondo physics survives this quench in well-defined regimes. Combining analytical renormalization-group theory for a Luttinger liquid with density matrix renormalization group (DMRG) simulations, we identify a transition from a strongly- to a weakly-entangled impurity as potential scattering is increased. The two approaches show excellent agreement concerning the stability of Kondo physics throughout the different parameter regimes considered. Our results provide a quantitative criterion for the emergence of Kondo screening in one-dimensional Yb gases and delineate experimentally accessible regimes for its realization in cold-atom platforms.

cond-mat.quant-gas↗

arXiv2025

Unraveling screening mechanisms in Kondo impurities using an NRG-MPS-based method

The Kondo effect is a hallmark of strongly-correlated systems, where an impurity's local degrees of freedom are screened by conduction electrons, forming a many-body singlet. With increasing degrees of freedom in the impurity, theoretical studies face significant challenges in accurately identifying and characterizing the underlying mechanisms that screen the impurity. In this work, we introduce a straightforward yet powerful methodology for identifying the formation of Kondo singlets and their screening mechanisms, by utilizing the numerical renormalization group (NRG) combined with the matrix product states (MPS) technique. We demonstrate the effectiveness of our method on the single and two-level Anderson impurity models (AIM). Furthermore, we discuss potential generalizations of the method to multichannel and multiorbital Kondo impurities. Harnessing advanced tensor network techniques, our approach extends to complex impurity systems, offering a robust and versatile framework for studying Kondo physics.

cond-mat.str-el↗

arXiv2023

Coherent exchange-coupled nonlocal Kondo impurities

Quantum dots exhibit a variety of strongly correlated effects, e.g., when tuned to emulate localized magnetic impurities that form a Kondo singlet with their surrounding environment. Interestingly, in double-dots setups, the magnetic impurities couple to each other by direct Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, which wins over the Kondo physics. In this work, we investigate a double-dot device where the dots are coupled via off-resonant ballistic whispering gallery modes, dubbed electronic cavity modes. Within this cavity-double-dot system, we study, using variational matrix product state techniques, the competition between Kondo formation and the coherent RKKY-like interaction that the cavity facilitates. Specifically, we find that (i) Kondo can win and form on each dot individually, or (ii) the cavity can win and mediate between the two dots either a singlet or a novel nonlocal Kondo-like effect phase, which we call "cat Kondo". We systematically study the quantum phase transitions between the different many-body states. Our discoveries lay the foundation for the experimental observation of unconventional nonlocal magnetic impurities.

cond-mat.str-el↗

arXiv2022

Entanglement based observables for quantum impurities

Quantum impurities exhibit fascinating many-body phenomena when the small interacting impurity changes the physics of a large noninteracting environment. The characterisation of such strongly correlated non-perturbative effects is particularly challenging due to the infinite size of the environment, and the inability of local correlators to capture the build-up of long-ranged entanglement in the system. Here, we harness an entanglement-based observable - the purity of the impurity - as a witness for the formation of strong correlations. We showcase the utility of our scheme by exactly solving the open Kondo box model in the small box limit, and thus describe all-electronic dot-cavity devices. Specifically, we conclusively characterise the metal-to-insulator phase transition in the system and identify how the (conducting) dot-lead Kondo singlet is quenched by an (insulating) intra-impurity singlet formation. Furthermore, we propose an experimentally feasible tomography protocol for the measurement of the purity, which motivates the observation of impurity physics through their entanglement build-up.

cond-mat.mes-hall↗