arXiv subjects

Michał P. Kwasigroch

Publications and source records attributed to Michał P. Kwasigroch.

2 recordsLinked to original sources

arXiv2026

Kondo singlet from ferromagnetic coupling: an analog of Anderson-Morel superconductivity in the magnetic channel

We consider magnetic impurities coupled to a conduction sea via a fully isotropic ferromagnetic spin-exchange term, the strength of which depends on the conduction-electron modes involved in the scattering. In the single-impurity case we show both analytically and numerically that there exists a parameter regime in which the conventional Kondo effect develops at low temperatures, leading to a singlet ground state. In the case of a lattice of impurities, we show that this leads to a heavy Fermi liquid state that is energetically favored over magnetic ordering in a broad parameter range. We argue that these effects are analogs of Anderson-Morel superconductivity, and discuss routes to their experimental realization.

cond-mat.str-el↗

arXiv2026

Inverted anisotropy of the partially screened magnetic impurity

We investigate a single magnetic impurity in the presence of strong spin-orbit coupling and single-ion anisotropy. We show that at sufficiently strong coupling there exists a finite temperature window, before the moment is completely screened, where the magnetic anisotropy of the system flips: the hard-axis becomes the easy-axis or vice versa. We derive this rigorously for a single impurity using numerical renormalization group calculations as well as Nozieres' strong-coupling limit and discuss its relevance to heavy-fermion compounds which order magnetically along the hard-direction. We show that the coexistence of Curie-like response and Kondo fluctuations is stabilized along the initially hard direction leading to the anisotropy switch.

cond-mat.str-el↗