Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1507.00271 · Europhysics Letters (EPL)

Self-ordered stationary states of driven quantum degenerate gases in optical resonators

R. M. Sandner, Wolfgang Niedenzu, Francesco Piazza, Helmut Ritsch

Published Sep 1, 2015• 18 citations
arXivHTMLPDF

Abstract

We study the role of quantum statistics in the self-ordering of ultracold bosons and fermions moving inside an optical resonator with transverse coherent pumping. For few particles we numerically compute the nonequilibrium dynamics of the density matrix towards the self-ordered stationary state of the coupled atom-cavity system. We include quantum fluctuations of the particles and the cavity field. These fluctuations in conjunction with cavity cooling determine the stationary distribution of the particles, which exhibits a transition from a homogeneous to a spatially ordered phase with the appearance of a superradiant scattering peak in the cavity output spectrum. While the ordering threshold is generally lower for bosons, we confirm the recently predicted zero pump strength threshold for superradiant scattering for fermions when the cavity photon momentum coincides with twice the Fermi momentum.

DOI
10.1209/0295-5075/111/53001

Related papers

Observation of a superradiant quantum phase transition in an intracavity degenerate Fermi gas

Xiaotian Zhang, Yu Chen, Zemao Wu +4 more

Coupling Bose-Einstein condensates to optical cavities has enabled the study of many-body states with long-range interactions. However, equivalent experiments with ultracold Fermi gases have remained largely unexplored. Here, we report an experimental realization of a superradiant quantum phase transition of a degenerate Fermi gas in a transversely pumped optical cavity. The self-ordering checkerboard density pattern of Fermi gases and superradiant transitions of the cavity field spontaneously emerge by increasing the pumping intensity above a threshold value. The effects of Fermi statistics are manifested by an inverse square root scaling of the threshold with atom number and the slow dynamics of low–atomic momentum states. Our work provides an ideal platform for studying nonequilibirium dynamics of many-body states for long-range interacting Fermi gases.

Science•Aug 26, 2021•95 citations

Density Wave Ordering with Disordered Ultracold Fermions in Optical Cavities

Óscar Rios Alves, Filippo Ferrari, Lorenzo Fioroni +2 more

We investigate the interplay between cavity-induced density-wave ordering and controllable disorder in a trapped two-dimensional gas of ultracold fermions. The atoms are dispersively coupled to an optical cavity and transversely driven by a pump beam, while an additional speckle beam spatially modulates the atom-light coupling through an AC-Stark shift of the atomic transition. In momentum space, this disorder converts the usual coupling between the cavity mode and a discrete set of density-wave Fourier components into a coupling to a continuum of fermionic density modes, weighted by the spectrum of the speckle pattern. Using linear response theory, we derive the superradiant threshold and show that the disordered interaction renormalizes the effective light-matter coupling, lowering the critical pump strength on average, with the threshold becoming self-averaging for short speckle correlation lengths. We complement this analysis with a numerical mean-field treatment that gives access to the intracavity photon number and to the real-space fermion density across the transition. These results confirm that the disorder shifts the photonic phase boundary and, above threshold, distorts the density-wave crystal by populating Fourier components beyond those selected by the clean cavity geometry. Our findings identify both the emitted cavity light and in situ density images as probes of engineered disorder in fermionic matter coupled to optical cavities.

cond-mat.quant-gasCross-listedarXiv:2606.30769•Jul 1, 2026•0 citations

Fermionic Superradiance in a Transversely Pumped Optical Cavity

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

Following the experimental realization of Dicke superradiance in Bose gases coupled to cavity light fields, we investigate the behavior of ultracold fermions in a transversely pumped cavity. We focus on the equilibrium phase diagram of spinless fermions coupled to a single cavity mode and establish a zero temperature transition to a superradiant state. In contrast to the bosonic case, Pauli blocking leads to lattice commensuration effects that influence self-organization in the cavity light field. This includes a sequence of discontinuous transitions with increasing atomic density and tricritical superradiance. We discuss the implications for experiment.

arXiv:1309.2464•Physical Review Letters•Apr 8, 2014•130 citations

Observation of localization-driven zero-threshold fermionic superradiance

Jijie Fan, Zimo Yang, Xue Zhang +3 more

Understanding the interplay between collective optical response and disorder presents significant challenges in modern many-body physics. While there has been considerable interest and a wealth of theoretical work in recent years, the experimental investigation of the superradiant phase transition and disorder has been unexplored. Here, we report an observation of the localization-driven superradiance with a degenerate Fermi gas in an optical cavity. We show that the dynamics of Fermi gases exhibits Anderson localization in an intracavity incommensurate lattice. The exponential localization is directly observed in both spatial and momentum spaces. We observe the localization driving a nearly vanishing pump threshold in fermionic superradiance when the system is in the localized state. The underlying mechanism of the self-organization and the quantum statistic of the atoms are revealed by measuring the atom momentum distribution and characteristic growth of the superradiant field. Our work provides a platform for studying superradiant quantum phase transition and localization in photon-mediated long-range interacting Fermi gases.

Science Advances•Sep 4, 2026•0 citations

Cavity-induced intertwining of density and pairing order in a degenerate Fermi gas

Sankalp Sharma, Farokh Mivehvar, Helmut Ritsch +1 more

Recent quantum gas cavity-QED experiments demonstrated simultaneous coupling of photons to single atom transitions as well as correlated pairs of ultracold fermions trapped inside optical cavities. This enables simultaneous control over density ordering and pairing. Using extensive numerical simulations, we show that in a transversely driven, two-component degenerate Fermi gas, the interplay of cavity-induced and bare atom--atom interactions controls not only the power threshold for self-organization, but also the type of spatial ordering in the $\mathbb Z_2$-symmetry-broken superradiant state. In the repulsive interaction regime, unpaired or weakly paired fermions first self-organize through a charge-density-wave instability, and finite-momentum pairing only occurs at much stronger pump strengths. In contrast, an attractive superfluid undergoes a joint density--pairing instability, directly entering into intertwined phase with charge-density-wave and pair-density-wave orders. At strong pumping the photon-enhanced pair interaction generates localized density and pairing order even when the bare contact interaction is repulsive. In this cavity-dominated regime strong spatial localization suppresses the long range superfluid coherence. Our results identify the role of cavity-induced atomic interactions in supporting intertwined fermionic orders and pave the way for exploring exotic states with multiple orders in highly controlled hybrid light-matter systems.

cond-mat.quant-gasCross-listedarXiv:2609.18800•Sep 17, 2026•0 citations

Quench Instabilities of a Strongly Interacting Quantum Gas in an Optical Cavity

Filip Marijanović, Sambuddha Chattopadhyay, Luka Skolc +6 more

Recent quench experiments on ultracold atoms in optical cavities provide a clean platform for studying how long-range interactions in atomic media structure their nonequilibrium dynamics. Motivated by these experiments, we provide a theoretical analysis of the quench instabilities that lead to the formation of superradiance as the hybrid system is driven across the self-organization transition. Working with both ultracold bosonic and fermionic gases, we compute the rate at which order forms and quantify the fluctuations of the prequench state that seed the instability. Our results quantitatively match existing experiments on free fermions and make predictions for quench experiments involving interacting Bose and Fermi gases. Our Letter suggests that the nonlocal nature of the photon-mediated interactions generates ordering dynamics that are qualitatively different than those observed in short-range interacting systems.

Physical Review Letters•Apr 9, 2026•0 citations
We study the role of quantum statistics in the self-ordering of ultracold bosons and fermions moving inside an optical resonator with transverse coherent pumping. For few particles we numerically compute the nonequilibrium dynamics of the density matrix towards the self-ordered stationary state of the coupled atom-cavity system. We include quantum fluctuations of the particles and the cavity field. These fluctuations in conjunction with cavity cooling determine the stationary distribution of the particles, which exhibits a transition from a homogeneous to a spatially ordered phase with the appearance of a superradiant scattering peak in the cavity output spectrum. While the ordering threshold is generally lower for bosons, we confirm the recently predicted zero pump strength threshold for superradiant scattering for fermions when the cavity photon momentum coincides with twice the Fermi momentum.
Coupling Bose-Einstein condensates to optical cavities has enabled the study of many-body states with long-range interactions. However, equivalent experiments with ultracold Fermi gases have remained largely unexplored. Here, we report an experimental realization of a superradiant quantum phase transition of a degenerate Fermi gas in a transversely pumped optical cavity. The self-ordering checkerboard density pattern of Fermi gases and superradiant transitions of the cavity field spontaneously emerge by increasing the pumping intensity above a threshold value. The effects of Fermi statistics are manifested by an inverse square root scaling of the threshold with atom number and the slow dynamics of low–atomic momentum states. Our work provides an ideal platform for studying nonequilibirium dynamics of many-body states for long-range interacting Fermi gases.
We investigate the interplay between cavity-induced density-wave ordering and controllable disorder in a trapped two-dimensional gas of ultracold fermions. The atoms are dispersively coupled to an optical cavity and transversely driven by a pump beam, while an additional speckle beam spatially modulates the atom-light coupling through an AC-Stark shift of the atomic transition. In momentum space, this disorder converts the usual coupling between the cavity mode and a discrete set of density-wave Fourier components into a coupling to a continuum of fermionic density modes, weighted by the spectrum of the speckle pattern. Using linear response theory, we derive the superradiant threshold and show that the disordered interaction renormalizes the effective light-matter coupling, lowering the critical pump strength on average, with the threshold becoming self-averaging for short speckle correlation lengths. We complement this analysis with a numerical mean-field treatment that gives access to the intracavity photon number and to the real-space fermion density across the transition. These results confirm that the disorder shifts the photonic phase boundary and, above threshold, distorts the density-wave crystal by populating Fourier components beyond those selected by the clean cavity geometry. Our findings identify both the emitted cavity light and in situ density images as probes of engineered disorder in fermionic matter coupled to optical cavities.
Following the experimental realization of Dicke superradiance in Bose gases coupled to cavity light fields, we investigate the behavior of ultracold fermions in a transversely pumped cavity. We focus on the equilibrium phase diagram of spinless fermions coupled to a single cavity mode and establish a zero temperature transition to a superradiant state. In contrast to the bosonic case, Pauli blocking leads to lattice commensuration effects that influence self-organization in the cavity light field. This includes a sequence of discontinuous transitions with increasing atomic density and tricritical superradiance. We discuss the implications for experiment.
Understanding the interplay between collective optical response and disorder presents significant challenges in modern many-body physics. While there has been considerable interest and a wealth of theoretical work in recent years, the experimental investigation of the superradiant phase transition and disorder has been unexplored. Here, we report an observation of the localization-driven superradiance with a degenerate Fermi gas in an optical cavity. We show that the dynamics of Fermi gases exhibits Anderson localization in an intracavity incommensurate lattice. The exponential localization is directly observed in both spatial and momentum spaces. We observe the localization driving a nearly vanishing pump threshold in fermionic superradiance when the system is in the localized state. The underlying mechanism of the self-organization and the quantum statistic of the atoms are revealed by measuring the atom momentum distribution and characteristic growth of the superradiant field. Our work provides a platform for studying superradiant quantum phase transition and localization in photon-mediated long-range interacting Fermi gases.
Recent quantum gas cavity-QED experiments demonstrated simultaneous coupling of photons to single atom transitions as well as correlated pairs of ultracold fermions trapped inside optical cavities. This enables simultaneous control over density ordering and pairing. Using extensive numerical simulations, we show that in a transversely driven, two-component degenerate Fermi gas, the interplay of cavity-induced and bare atom--atom interactions controls not only the power threshold for self-organization, but also the type of spatial ordering in the Z2\mathbb Z_2Z2​-symmetry-broken superradiant state. In the repulsive interaction regime, unpaired or weakly paired fermions first self-organize through a charge-density-wave instability, and finite-momentum pairing only occurs at much stronger pump strengths. In contrast, an attractive superfluid undergoes a joint density--pairing instability, directly entering into intertwined phase with charge-density-wave and pair-density-wave orders. At strong pumping the photon-enhanced pair interaction generates localized density and pairing order even when the bare contact interaction is repulsive. In this cavity-dominated regime strong spatial localization suppresses the long range superfluid coherence. Our results identify the role of cavity-induced atomic interactions in supporting intertwined fermionic orders and pave the way for exploring exotic states with multiple orders in highly controlled hybrid light-matter systems.
Recent quench experiments on ultracold atoms in optical cavities provide a clean platform for studying how long-range interactions in atomic media structure their nonequilibrium dynamics. Motivated by these experiments, we provide a theoretical analysis of the quench instabilities that lead to the formation of superradiance as the hybrid system is driven across the self-organization transition. Working with both ultracold bosonic and fermionic gases, we compute the rate at which order forms and quantify the fluctuations of the prequench state that seed the instability. Our results quantitatively match existing experiments on free fermions and make predictions for quench experiments involving interacting Bose and Fermi gases. Our Letter suggests that the nonlocal nature of the photon-mediated interactions generates ordering dynamics that are qualitatively different than those observed in short-range interacting systems.