Fermionic Superradiance in a Transversely Pumped Optical Cavity

Keeling, Jonathan; Bhaseen, M. J.; Simons, Benjamin D.

doi:10.1103/physrevlett.112.143002

Cited by 101 publications

(93 citation statements)

References 45 publications

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“…Above a critical pump strength, the occupation of the cavity mode is stabilized and the bosonic atoms organize into a checkerboard density pattern [12]. Many different proposals have been put forward to realize the self-organization of more complex quantum phases [13] reaching from the Mott-insulator [15] over fermionic phases [16][17][18][19][20] and disordered structures [21][22][23][24] to phases with spin-orbit coupling [25][26][27].…”

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confidence: 99%

Ultracold Fermions in a Cavity-Induced Artificial Magnetic Field

et al. 2016

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We show how a fermionic quantum gas in an optical lattice and coupled to the field of an optical cavity can self-organize into a state in which the spontaneously emerging cavity field amplitude induces an artificial magnetic field. The fermions form either a chiral insulator or a chiral liquid carrying edge currents. The feedback mechanism via the cavity field enables robust and fast switching of the edge currents and the cavity output can be employed for non-destructive measurements of the atomic dynamics. The controlled generation of topologically non-trivial quantum phases is of greatest interest since they possess special properties such as extended edge states that can be well protected against destructive environmental effects[1]. Thus, materials with topological non-trivial properties have the prospect to be utilized for quantum devices and quantum computing. Well known are topological insulators with protected edge currents created in quantum Hall devices [2] by strong magnetic fields.For neutral atoms strong artificial magnetic fields can be created [3] which act similarly as magnetic fields for charged particles. Such artificial magnetic fields have been used in quantum gases confined to optical lattices to realize two showcase models of topologically insulating phases, the Hofstadter model in two-dimensions [4][5][6][7] or on a ladder geometry [8] and the Haldane model [9].Yet, the dynamic control and detection of topologically non-trivial quantum states remains a great challenge. In order to overcome this difficulty, in this work the dynamical feedback between atoms and an optical cavity is employed to reach a self-organization of topologically non-trivial phases. One fascinating example for a selforganization of a coupled atom-cavity system has been realized recently by placing a bosonic quantum gas into an optical high-finesse resonator subjected to a perpendicular off-resonant pump beam [10][11][12][13][14]. Above a critical pump strength, the occupation of the cavity mode is stabilized and the bosonic atoms organize into a checkerboard density pattern [12]. Many different proposals have been put forward to realize the self-organization of more complex quantum phases [13] reaching from the Mott-insulator [15] over fermionic phases [16][17][18][19][20] and disordered structures [21][22][23][24] to phases with spin-orbit coupling [25][26][27].In this work, we engineer a direct coupling mechanism of the cavity photons to the tunneling of atoms in an optical lattice. This is achieved using a Raman transition induced by the combination of a transverse pump beam and the cavity field (Fig. 1). The frequencies of the pump beam and the cavity mode are chosen such that the energy transfer is close to the energy offset between neigh- boring lattice sites. The resulting process represents an effective tunneling of the atoms. Due to the running-wave nature of the pump beam, a phase ϕ can be imprinted onto the tunneling of the atoms around a plaquette in the presence of cavity photons. We demonstrate that due t...

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confidence: 99%

Ultracold Fermions in a Cavity-Induced Artificial Magnetic Field

et al. 2016

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“…Moreover, the atoms typically respond to the photon variation on an even longer time scale such that the photon dynamics can be treated adiabatically [24,25]. In this case, the steady-state solution of the system can be approximated by the stationary condition ∂α/∂t = 0 [31][32][33], which leads to…”

Section: Modelmentioning

confidence: 99%

“…This corresponds to the nesting condition discussed in Refs. [31][32][33], under which a spinless Fermi gas coupled to a cavity field can have enhanced superradiance. Here, as the system is already in the SR state when the SR-TSR phase boundary is crossed, satisfaction of the nesting condition leads to a peak in the variation of the cavity field instead.…”

Section: Back-action Of the Cavity Field Across The Topological Phasementioning

confidence: 99%

“…Furthermore, it was later demonstrated that the dynamical structure factor of the BEC can also be probed by monitoring the photons leaking from the cavity [30]. It has been shown theoretically that when the BEC is replaced by a spinless degenerate Fermi gas, the SR cavity field opens a bulk gap at the Fermi surface, whereas the back-action of the Fermi gas gives rise to enhancement of the superradiance due to the nesting effect [31][32][33].…”

Section: Introductionmentioning

confidence: 99%

“…This is essentially the nesting effect discussed in Refs. [31][32][33] for a spinless Fermi gas in a cavity. We show that the nesting effect here leads to a peak structure in the variation of the cavity photon occupation at the topological boundary, which can be used as a clear signature of the topological phase transition.…”

Section: Introductionmentioning

confidence: 99%

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Topological superradiant state in Fermi gases with cavity induced spin–orbit coupling

Pan

Liu

et al. 2017

Front. Phys.

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Coherently driven atomic gases inside optical cavities hold great promise for generating rich dynamics and exotic states of matter. It was shown recently that an exotic topological superradiant state exists in a two-component degenerate Fermi gas coupled to a cavity, where local order parameters coexist with global topological invariants. In this work, we characterize in detail various properties of this exotic state, focusing on the feedback interactions between the atoms and the cavity field. In particular, we demonstrate that cavity-induced interband coupling plays a crucial role in inducing the topological phase transition between the conventional and topological superradiant states. We analyze the interesting signatures in the cavity field left by the closing and reopening of the atomic bulk gap across the topological phase boundary and discuss the robustness of the topological superradiant state by investigating the steady-state phase diagram under various conditions. Furthermore, we consider the interaction effect and discuss the interplay between the pairing order in atomic ensembles and the superradiance of the cavity mode. Our work provides many valuable insights into the unique cavity-atom hybrid system under study and is helpful for future experimental exploration of the topological superradiant state.

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