Lattice Bose polarons at strong coupling and quantum criticality
Al Hyder R, Colussi VE, Čufar M, Brand J, Recati A, Bruun GM. 2025. Lattice Bose polarons at strong coupling and quantum criticality. Scipost Physics. 19(1), 002.
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Author
Al Hyder, RagheedISTA;
Colussi, Victor E.;
Čufar, Matija;
Brand, Joachim;
Recati, Alessio;
Bruun, Georg M.
Corresponding author has ISTA affiliation
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Abstract
The problem of mobile impurities in quantum baths is of fundamental importance in many-body physics. There has recently been significant progress regarding our understanding of this due to cold atom experiments, but so far it has mainly been concerned with cases where the bath has no or only weak interactions, or the impurity interacts weakly with the bath. Here, we address this gap by developing a new theoretical framework for exploring a mobile impurity interacting strongly with a highly correlated bath of bosons in the quantum critical regime of a Mott insulator (MI) to superfluid (SF) quantum phase transition. Our framework is based on a powerful quantum Gutzwiller (QGW) description of the bosonic bath combined with diagrammatic field theory for the impurity-bath interactions. By resumming a selected class of diagrams to infinite order, a rich picture emerges where the impurity is dressed by the fundamental modes of the bath, which change character from gapped particle-hole excitations in the MI to Higgs and gapless Goldstone modes in the SF. This gives rise to the existence of several quasiparticle (polaron) branches with properties reflecting the strongly correlated environment. In particular, one polaron branch exhibits a sharp cusp in its energy, while a new ground-state polaron emerges at the O(2) quantum phase transition point for integer filling, which reflects the nonanalytic behavior at the transition and the appearance of the Goldstone mode in the SF phase. Smooth versions of these features are inherited in the polaron spectrum away from integer filling due to the influence of Mott physics on the bosonic bath. We furthermore compare our diagrammatic results with quantum Monte Carlo calculations, obtaining excellent agreement. This accuracy is quite remarkable for such a highly non-trivial case of strong interactions between the impurity and bosons in a maximally correlated quantum critical regime, and it establishes the utility of our framework. Finally, our results show how impurities can be used as quantum sensors and highlight fundamental differences between experiments performed at a fixed particle number or a fixed chemical potential.
Publishing Year
Date Published
2025-07-01
Journal Title
Scipost Physics
Publisher
SciPost Foundation
Volume
19
Issue
1
Article Number
002
eISSN
IST-REx-ID
Cite this
Al Hyder R, Colussi VE, Čufar M, Brand J, Recati A, Bruun GM. Lattice Bose polarons at strong coupling and quantum criticality. Scipost Physics. 2025;19(1). doi:10.21468/SciPostPhys.19.1.002
Al Hyder, R., Colussi, V. E., Čufar, M., Brand, J., Recati, A., & Bruun, G. M. (2025). Lattice Bose polarons at strong coupling and quantum criticality. Scipost Physics. SciPost Foundation. https://doi.org/10.21468/SciPostPhys.19.1.002
Al Hyder, Ragheed, Victor E. Colussi, Matija Čufar, Joachim Brand, Alessio Recati, and Georg M. Bruun. “Lattice Bose Polarons at Strong Coupling and Quantum Criticality.” Scipost Physics. SciPost Foundation, 2025. https://doi.org/10.21468/SciPostPhys.19.1.002.
R. Al Hyder, V. E. Colussi, M. Čufar, J. Brand, A. Recati, and G. M. Bruun, “Lattice Bose polarons at strong coupling and quantum criticality,” Scipost Physics, vol. 19, no. 1. SciPost Foundation, 2025.
Al Hyder R, Colussi VE, Čufar M, Brand J, Recati A, Bruun GM. 2025. Lattice Bose polarons at strong coupling and quantum criticality. Scipost Physics. 19(1), 002.
Al Hyder, Ragheed, et al. “Lattice Bose Polarons at Strong Coupling and Quantum Criticality.” Scipost Physics, vol. 19, no. 1, 002, SciPost Foundation, 2025, doi:10.21468/SciPostPhys.19.1.002.
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