Magnetic order in a Fermi gas induced by cavity-field fluctuations

Fan, Jingtao; Zhou, Xiaofan; Zheng, W. J.; Wu, Yi; Chen, Gang; Jia, Suotang

doi:10.1103/physreva.98.043613

Cited by 24 publications

(16 citation statements)

References 65 publications

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“…On a mean-field level, a very similar phase diagram could be realized for bosonic species. Quantum statistics will play a fundamental role for low photon numbers where the mean-field approximation breaks down, which gives rise to new phases [32]. On our level of approximation the essential signatures arising from the Fermi statistics are found in the two-body momentum correlations.…”

Section: Discussionmentioning

confidence: 95%

“…With the prediction of new intriguing phenomena such as Umklapp superradiance [26,27], topologically protected edge states [28,29], superconducting pairing [30,31], artificial dynamic gauge fields [20], unconventional momentum correlations and quantum phases in multiple dimensions [32][33][34][35], implementations of fermionic systems coupled to cavity fields have gained more attention recently. In the present article, we propose the realization of density and spin self-ordering for a transversely driven multi-level Fermi gas coupled to a pair of counterpropagating degenerate modes of a ring cavity as depicted in figure 1 [36][37][38][39][40][41][42].…”

Section: Introductionmentioning

confidence: 99%

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Antiferromagnetic self-ordering of a Fermi gas in a ring cavity

et al. 2019

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We explore the density and spin self-ordering of driven spin-1/2 collisionless fermionic atoms coupled to the electromagnetic fields of a ring resonator. The two spin states are two-photon Ramancoupled via a pair of degenerate counterpropagating cavity modes and two transverse pump fields. In this one-dimensional configuration the coupled atom-field system possesses a continuous U(1) translational symmetry and a discrete Z 2 spin inversion symmetry. At half filling for sufficiently strong pump strengths, the combined U(1)×Z 2 symmetry is spontaneously broken at the onset of a superradiant phase transition to a state with self-ordered density and spin structures. We predominately find an antiferromagnetic lattice order at the cavity wavelength. The self-ordered states exhibit unexpected positive momentum pair correlations between fermions with opposite spin. These strong cavity-mediated correlations vanish at higher pump strength.

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Section: Discussionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Antiferromagnetic self-ordering of a Fermi gas in a ring cavity

et al. 2019

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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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“…These systems exhibit many more interesting phenomena, including the emergence of synthetic strong magnetic fields and spin-orbit coupling [46][47][48][49], disorder-driven density and spin self-ordering [50], topological states [51,52], and a variety of magnetic Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. orders [53,54]. Very recently, first experimental implementations showing spin self-ordering in a spin-1 BEC in a standing wave cavity were realized [55,56].…”

Section: Introductionmentioning

confidence: 99%

Cavity-induced emergent topological spin textures in a Bose–Einstein condensate

et al. 2019

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The coupled nonlinear dynamics of ultracold quantum matter and electromagnetic field modes in an optical resonator exhibits a wealth of intriguing collective phenomena. Here we study a Λ-type, threecomponent Bose-Einstein condensate coupled to four dynamical running-wave modes of a ring cavity, where only two of the modes are externally pumped. However, the unpumped modes play a crucial role in the dynamics of the system due to coherent backscattering of photons. On a mean-field level we identify three fundamentally different steady-state phases with distinct characteristics in the density and spatial spin textures: a combined density and spin-wave, a continuous spin spiral with a homogeneous density, and a spin spiral with a modulated density. The spin-spiral states, which are topological, are intimately related to cavity-induced spin-orbit coupling emerging beyond a critical pump power. The topologically trivial density-wave-spin-wave state has the characteristics of a supersolid with two broken continuous symmetries. The transitions between different phases are either simultaneously topological and first-order, or second-order. The proposed setup allows the simulation of intriguing many-body quantum phenomena by solely tuning the pump amplitudes and frequencies, with the cavity output fields serving as a built-in nondestructive observation tool. New J. Phys. 21 (2019) 013029 S Ostermann et al *

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Magnetic order in a Fermi gas induced by cavity-field fluctuations

Cited by 24 publications

References 65 publications

Antiferromagnetic self-ordering of a Fermi gas in a ring cavity

Antiferromagnetic self-ordering of a Fermi gas in a ring cavity

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

Cavity-induced emergent topological spin textures in a Bose–Einstein condensate

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