Abstract
Understanding the nature of confinement, as well as its relation with the spontaneous breaking of chiral symmetry, remains one of the long-standing questions in high-energy physics. The difficulty of this task stems from the limitations of current analytical and numerical techniques to address non-perturbative phenomena in non-Abelian gauge theories. In this work, we show how similar phenomena emerge in simpler models, and how these can be further investigated using state-of-the-art cold-atom quantum simulators. More specifically, we introduce the rotor Jackiw-Rebbi model, a (1+1)-dimensional quantum field theory where interactions between Dirac fermions are mediated by quantum rotors. Starting from a mixture of ultracold atoms in an optical lattice, we show how this quantum field theory emerges in the long-wavelength limit. For a wide and experimentally-relevant parameter regime, the Dirac fermions acquire a dynamical mass via the spontaneous breakdown of chiral symmetry. Moreover, we study the effect of both quantum and thermal fluctuations, which lead to the phenomenon of chiral symmetry restoration. Finally, we uncover a confinement-deconfinement quantum phase transition, where meson-like fermions fractionalise into quark-like quasi-particles bound to topological solitons of the rotor field. The proliferation of these solitons at finite chemical potentials again serves to restore the chiral symmetry, yielding a clear analogy with the quark-gluon plasma in quantum chromodynamics, where this symmetry coexists with the deconfined fractional charges. Our results show how the interplay between these phenomena could be analyse in realistic atomic experiments.
Highlights
Quantum field theory (QFT) provides a unifying framework to understand many-body systems at widely different scales
We study several high-energy nonperturbative phenomena using a neat (1 + 1) quantum field theory, the rotor Jackiw-Rebbi model, and propose a quantumsimulation scheme using a Fermi-Bose mixture of ultracold atoms in an optical lattice
Dirac fermions, whose interactions are mediated by spin-S rotors in this model, acquire a dynamical mass through the spontaneous breaking of chiral symmetry
Summary
Quantum field theory (QFT) provides a unifying framework to understand many-body systems at widely different scales. In the vicinity of certain SSB phase transitions, the quasiparticles governing the long-wavelength phenomena can be completely different from the original nonrelativistic constituents [5], and even be described by relativistic models analogous to those of particle physics It is the careful understanding of this quasiparticle renormalization, which yields the very definition of a relativistic QFT [6,7,8], and sets the basis for the nonperturbative approach to lattice gauge theories [9,10]. We follow this route, and identify a simple lattice model in (1 + 1) dimensions that regularizes a relativistic QFT, where the interplay between dynamical mass generation and charge fractionalization leads to confinement-deconfinement transitions of quarklike quasiparticles, the mechanism of which can be neatly understood at the microscopic level.
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