Cavity-Mediated Unconventional Pairing in Ultracold Fermionic Atoms

Schlawin, Frank; Jaksch, Dieter

doi:10.1103/physrevlett.123.133601

Cited by 40 publications

(26 citation statements)

References 89 publications

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“…Therefore, they are largely independent of the electron band dispersion and can be induced on top of existing interactions. These induced interactions could be used to control or enhance existing instabilities or give rise to different quantum states through competition with other short-range interactions [78][79][80][81]. To date, engineered long-range quantum fluctuation-mediated interactions have mainly been studied in the context of ultracold atoms [78,[82][83][84][85][86][87][88][89][90][91][92][93].…”

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confidence: 99%

Photoinduced Electron Pairing in a Driven Cavity

et al. 2020

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We demonstrate how virtual scattering of laser photons inside a cavity via two-photon processes can induce controllable long-range electron interactions in two-dimensional materials. We show that laser light that is red (blue) detuned from the cavity yields attractive (repulsive) interactions whose strength is proportional to the laser intensity. Furthermore, we find that the interactions are not screened effectively except at very low frequencies. For realistic cavity parameters, laser-induced heating of the electrons by inelastic photon scattering is suppressed and coherent electron interactions dominate. When the interactions are attractive, they cause an instability in the Cooper channel at a temperature proportional to the square root of the driving intensity. Our results provide a novel route for engineering electron interactions in a wide range of two-dimensional materials including AB-stacked bilayer graphene and the conducting interface between LaAlO 3 and SrTiO 3 .

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confidence: 99%

Photoinduced Electron Pairing in a Driven Cavity

et al. 2020

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“…We note that we have also taken the q 0 → 0 limit of U q in the MF definition and in the gap equation Eq. ( 3) [65].…”

Section: Resultsmentioning

confidence: 99%

Higgs mode stabilization by photo-induced long-range interactions in a superconductor

Gao,

Schlawin,

Jaksch

2021

Preprint

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We show that low-lying excitations of a 2D BCS superconductor are significantly altered when coupled to an externally driven cavity, which induces controllable long-range attractive interactions between the electrons. We find that they combine non-linearly with intrinsic local interactions to increase the Bogoliubov quasiparticle excitation energies, thus enlarging the superconducting gap. The long-range nature of the driven-cavity-induced attraction qualitatively changes the collective excitations of the superconductor. Specifically, they lead to the appearance of additional collective excitations of the excitonic modes. Furthermore, the Higgs mode is pushed into the gap and now lies below the Bogoliubov quasiparticle continuum such that it cannot decay into quasiparticles. This way, the Higgs mode's lifetime is greatly enhanced.

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“…In particular, one can measure light scattered at an angle that does not satisfy the condition (1), which would contain different information about the distribution of the atoms [58][59][60][61] . The feedback-induced maximization of this signal might result in more exotic states of the atomic ensembles, both bosons and fermions 28,29,[62][63][64][65][66][67][68][69][70] . We leave this interesting possibility for future research.…”

Section: Resultsmentioning

confidence: 99%

Cavityless self-organization of ultracold atoms due to the feedback-induced phase transition

Иванов

Ivanova

Caballero-Benítez

et al. 2020

Sci Rep

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feedback is a general idea of modifying system behavior depending on the measurement outcomes. It spreads from natural sciences, engineering, and artificial intelligence to contemporary classical and rock music. Recently, feedback has been suggested as a tool to induce phase transitions beyond the dissipative ones and tune their universality class. Here, we propose and theoretically investigate a system possessing such a feedback-induced phase transition. the system contains a Bose-einstein condensate placed in an optical potential with the depth that is feedback-controlled according to the intensity of the Bragg-reflected probe light. We show that there is a critical value of the feedback gain where the uniform gas distribution loses its stability and the ordered periodic density distribution emerges. Due to the external feedback, the presence of a cavity is not necessary for this type of atomic self-organization. We analyze the dynamics after a sudden change of the feedback control parameter. The feedback time constant is shown to determine the relaxation above the critical point. We show as well that the control algorithm with the derivative of the measured signal dramatically decreases the transient time. Feedback control is known to be a useful tool to modify dynamics of classical 1 as well as quantum systems 2. There were many theoretical proposals 3-13 and several experimental realizations 14-18 of quantum feedback control in optics and atomic physics. The feedback control of quantum systems is fundamentally different from that of classical systems mainly due to the inevitable measurement back-action 19. In most cases this quantum effect does not pose sever limitations on the feasibility of feedback control, but it has to be taken into account designing quantum control algorithms 20. Recently the feedback loop has been suggested as a tool to control phase transitions in quantum systems 21 and, in particular, in many-body settings 13,22. The feedback control of atomic self-organization has been recently demonstrated experimentally in 23. Thus the new class of feedback phase transitions (FPT) has been introduced, which can have properties beyond dissipative phase transitions in open systems. The key advantage of FPT is its extremely high degree of flexibility and controllability, which allows for the manipulation of the critical point and critical exponents and, therefore, enables the tuning and control of the universality class of phase transitions 21. In this report we apply the concept of FPT to a system based on Bragg light scattering from a Bose-Einstein condensate (BEC). Instead of the self-formed standing-wave potential 24,25 , we propose to use an actively controlled optical lattice with the control based on the Bragg-reflected signal of a probe light. The system with active feedback provides much higher degree of control on the distribution of atoms and its evolution around the critical point in comparison to systems without feedback. Such improved controllability can assist in quantum simulations, ...

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Cavity-Mediated Unconventional Pairing in Ultracold Fermionic Atoms

Cited by 40 publications

References 89 publications

Photoinduced Electron Pairing in a Driven Cavity

Photoinduced Electron Pairing in a Driven Cavity

Higgs mode stabilization by photo-induced long-range interactions in a superconductor

Cavityless self-organization of ultracold atoms due to the feedback-induced phase transition

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