Rashba Cavity QED: A Route Towards the Superradiant Quantum Phase Transition

Nataf, Pierre; Champel, Thierry; Blatter, G.; Basko, D. M.

doi:10.1103/physrevlett.123.207402

Cited by 56 publications

(64 citation statements)

References 52 publications

(57 reference statements)

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“…In the same manner, the critical magnetic fields are also enhanced. These facts are similar to the suggestion of T c enhancement through photon-matter coupling by Mazza and Georges 35 ; however, in their case, phase transition does not occur solely by photon-matter coupling, and their model does not guarantee gauge invariance 36,37 .…”

Section: Resultssupporting

confidence: 84%

“…Early reports on the SRPT suggested its no-go theorems [43][44][45][46] , implying that thermal-equilibrium SRPTs cannot be realized in systems described by the minimal-coupling Hamiltonian, that is, charged particles (without spins) interacting with electromagnetic fields. Because the classical treatment of the electromagnetic fields used in proofs of such no-go theorems can be justified only in limited situations 2,[45][46][47][48][49] , proposals of counter-examples against the no-go theorems and criticisms against the counter-examples have been repeated in SRPT research [35][36][37][50][51][52][53][54][55][56][57] .…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

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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Section: Resultssupporting

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Magnonic superradiant phase transition

Bamba

Peraca

et al. 2022

Commun Phys

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“…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%

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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“…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%