arXiv subjects

Hubert Dunikowski

Publications and source records attributed to Hubert Dunikowski.

4 recordsLinked to original sources

arXiv2026

Degeneracy-governed spin squeezing in high-spin Fermi-Hubbard systems weakly coupled to light

High-spin alkaline-earth fermions in optical lattices are promising platforms for spin squeezing beyond the spin-1/2 paradigm. We show that spin-squeezing dynamics is qualitatively modified by degeneracies inherent to the extended internal spin structure. We identify these degeneracies as the microscopic origin of the breakdown of the conventional maximal-spin description and develop an effective population-eigenstate framework that quantitatively reproduces the spin-squeezing dynamics. Our results establish degeneracy as a generic driver of collective spin dynamics in high-spin systems.

cond-mat.quant-gas↗

arXiv2026

Population eigenstates of the SU(d) spin-exchange model for high-spin fermions in optical lattices

We investigate the $\mathrm{SU}(d)$ spin exchange model describing ultra-cold fermionic atoms with spin $s\ge 1$ in a one-dimensional optical lattice. The model emerges from the Fermi-Hubbard model in the strongly interacting regime with one atom in each lattice site. The central result of this work is the systematic construction of eigenstates in terms of magnetic sub-level populations, which we call population eigenstates. Exploiting this framework, we derive effective light-induced Hamiltonians via a second-order Schrieffer-Wolff transformation projected onto the population eigenstates. The resulting models reveal a qualitative difference between spin-1/2 and higher-spin systems: whereas spin-1/2 dynamics remains confined to the maximal-spin Dicke manifold, the extensive $\mathrm{SU}(d)$ degeneracies for $s\ge 1$ allow coherent population transfer across sectors of different collective spin length, generating unconventional spin dynamics that cannot be captured by any fixed-spin-manifold description. Agreement with exact Fermi-Hubbard dynamics confirms the framework as a practical foundation for quantum-enhanced correlations and metrological protocols in high-spin fermionic systems.

cond-mat.quant-gas↗

arXiv2025

Magnetization-induced reordering of ground states phase diagram in a two-component Bose-Hubbard model

We investigate the influence of non-zero magnetization on the ground-state phase diagram of the two-component Bose-Hubbard model. Employing a mean-field theoretical framework, both analytically and numerically, we demonstrate that positions and sizes of specific phases on the diagram are magnetization dependent. In particular, non-zero magnetization introduces different Mott insulator phase boundaries for each of the two components. This effect leads to the emergence of a hybrid phase characterized by the coexistence of superfluid in one of the components and Mott insulator in the another one. Our findings highlight the important role of a conserved quantities, which is magnetization here, in reshaping the phase landscape, significantly influencing the stability and emergence of distinct quantum phases.

cond-mat.quant-gas↗

arXiv2024

Effective light-induced Hamiltonian for atoms with large nuclear spin

Ultra-cold fermionic atoms, having two valence electrons, exhibit a distinctive internal state structure, wherein the nuclear spin becomes decoupled from the electronic degrees of freedom in the ground electronic state. Consequently, the nuclear spin states are well isolated from the environment, rendering these atomic systems an opportune platform for quantum computation and quantum simulations. Coupling with off-resonance light is an essential tool to selectively and coherently manipulate the nuclear spin states. In this paper, we present a systematic derivation of the effective Hamiltonian for the nuclear spin states of ultra-cold fermionic atoms due to such an off-resonance light. We obtain compact expressions for the scalar, vector and tensor light shifts taking into account both linear and quadratic contributions to the hyperfine splitting. The analysis has been carried out using the Green operator approach and solving the corresponding Dyson equation. Finally, we analyze different scenarios of light configurations which lead to the vector- and tensor-light shifts, as well as the pure spin-orbit coupling for the nuclear spin.

quant-ph↗