Superradiant Phase Transition in Electronic Systems and Emergent Topological Phases

Guerci, Daniele; Simon, Pascal; Mora, Christophe

doi:10.1103/physrevlett.125.257604

Cited by 58 publications

(43 citation statements)

References 65 publications

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“…from which we conclude, in analogy with similar arguments for the Peierls substitution [37], that the TRK sum rule is satisfied for our projected Coulomb Hamiltonian. In fact, we can show this in quite some generality using gauge equivalence.…”

Section: B Coulomb Gauge Hamiltonian: Mean-field Solutionsupporting

confidence: 84%

“…This work suggests several possible extensions. From one side it would be interesting to broaden our model to consider a spatially varying vector potential, following the recent prediction of superradiance in such a setup [37,38]. Another promising direction would be to explore the residual light-matter coupling of finite frequency excitations and the possibility of turning them superradiant using a combination of drive and dissipation, as done in other nonequilibrium contexts.…”

Section: Discussionmentioning

confidence: 99%

“…Those ground-state realizations of the Dicke superradiance raise a number of conceptual questions, and even in a much simpler context of two-level systems, the phenomenon remains elusive and controversial [33][34][35]. Very recently, evidence for electronic superradiance beyond the no-go theorem has been demonstrated in the presence of a spatially varying electromagnetic field [36][37][38].…”

Section: Introductionmentioning

confidence: 99%

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Gauge fixing for strongly correlated electrons coupled to quantum light

Dmytruk

Schiró

2021

Phys. Rev. B

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We discuss the problem of gauge fixing for strongly correlated electrons coupled to quantum light, described by projected low-energy models such as those obtained within tight-binding methods. Drawing from recent results in the field of quantum optics, we present a general approach to write down a quantum light-matter Hamiltonian in either dipole or Coulomb gauge which is explicitly connected by a unitary transformation, thus ensuring gauge equivalence even after projection. The projected dipole gauge Hamiltonian features a linear light-matter coupling and an instantaneous self-interaction for the electrons, similar to the structure in the full continuum theory. On the other hand, in the Coulomb gauge the photon field enters in a highly nonlinear way, through phase factors that dress the electronic degrees of freedom. We show that our approach generalizes the well-known Peierls approximation, to which it reduces when only local, on-site orbital contributions to lightmatter coupling are taken into account. As an application we study a two-orbital model of interacting electrons coupled to a uniform cavity mode, recently studied in the context of excitonic superradiance and associated no-go theorems. Using both gauges we recover the absence of a superradiant phase in the ground state and show that excitations on top of it, described by polariton modes, contain instead nontrivial light-matter entanglement. Our results highlight the importance of treating the nonlinear light-matter interaction of the Coulomb gauge nonperturbatively, to obtain a well-defined ultrastrong coupling limit and to not spoil gauge equivalence.

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Section: B Coulomb Gauge Hamiltonian: Mean-field Solutionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Gauge fixing for strongly correlated electrons coupled to quantum light

Dmytruk

Schiró

2021

Phys. Rev. B

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“…For example, it has been shown that the Rashba spin-orbit coupling can cause paramagnetic instability in an ultrastrongly coupled system between a cyclotron resonance and cavity photon field, implying an SRPT 37 . Further, it has been pointed out recently 37,58,59 that the coupling between matter and a spatially-varying multi-mode cavity fields plays a key role for circumventing the no-go theorem. Another method is to utilize various types of interactions and spin waves in magnetic materials, which cannot be described by the minimal-coupling Hamiltonian.…”

Section: Discussionmentioning

confidence: 99%

Magnonic superradiant phase transition

Bamba

Peraca

et al. 2022

Commun Phys

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In the superradiant phase transition (SRPT), coherent light and matter fields are expected to appear spontaneously in a coupled light–matter system in thermal equilibrium. However, such an equilibrium SRPT is forbidden in the case of charge-based light–matter coupling, known as no-go theorems. Here, we show that the low-temperature phase transition of ErFeO3 at a critical temperature of approximately 4 K is an equilibrium SRPT achieved through coupling between Fe3+ magnons and Er3+ spins. By verifying the efficacy of our spin model using realistic parameters evaluated via terahertz magnetospectroscopy and magnetization experiments, we demonstrate that the cooperative, ultrastrong magnon–spin coupling causes the phase transition. In contrast to prior studies on laser-driven non-equilibrium SRPTs in atomic systems, the magnonic SRPT in ErFeO3 occurs in thermal equilibrium in accordance with the originally envisioned SRPT, thereby yielding a unique ground state of a hybrid system in the ultrastrong coupling regime.

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“…Theoretical proposals consider systems in the ultrastrong light-matter coupling regime [15] or use electron gases that either possess a Rashba spin-orbit coupling [16] or are subjected to a spatially varying electromagnetic field [16][17][18] or have the role of photons be played by magnons [19].…”

mentioning

confidence: 99%