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

Science

Dynamics of repulsive Fermi gases

Jelena Stajic

Published Jan 17, 2019• 0 citations
Publisher

Abstract

Physics Pump-probe techniques, in which a short light pulse knocks the system out of equilibrium and another pulse is then used to monitor the dynamics, are commonplace in solid-state physics. Amico et al. used such a technique in a fermionic atomic gas to study what happens when the gas is plunged into a regime where the atoms strongly repel one another. The nature of this regime in an even mixture of two spin states has been debated—a ferromagnetic state was expected, but instead the atoms had a tendency to form pairs. Here, the researchers disentangled the two pathways and found that correlations consistent with ferromagnetism initially increased faster than the pairs formed, but neither clearly dominated over the other. Phys. Rev. Lett. 121 , 253602 (2018).

DOI
10.1126/science.363.6424.242-d

Related papers

Time-Resolved Observation of Competing Attractive and Repulsive Short-Range Correlations in Strongly Interacting Fermi Gases

Andrea Amico, Francesco Scazza, Giacomo Valtolina +5 more

We exploit a time-resolved pump-probe spectroscopic technique to study the out-of-equilibrium dynamics of an ultracold two-component Fermi gas, selectively quenched to strong repulsion along the upper branch of a broad Feshbach resonance. For critical interactions, we find the rapid growth of short-range anticorrelations between repulsive fermions to initially overcome concurrent pairing processes. At longer evolution times, these two competing mechanisms appear to macroscopically coexist in a short-range correlated state of fermions and pairs, unforeseen thus far. Our work provides fundamental insights into the fate of a repulsive Fermi gas, and offers new perspectives towards the exploration of complex dynamical regimes of fermionic matter.

arXiv:1807.10208•Physical Review Letters•Dec 19, 2018•53 citations

Probing a quantum emulsion

Jelena Stajic

Quantum Gases Ultracold atomic gases with strongly repulsive interactions can be a useful model system for studying the emergence of itinerant ferromagnetism. However, the same atoms that can order magnetically are also prone to pairing into loosely bound molecules. If an atomic system is suddenly placed in a strongly interacting regime, both processes occur and an inhomogeneous, phase-separated state consisting of unpaired and paired atoms can form. Scazza et al. studied this state with a variety of probes. The data were consistent with the formation of a quantum emulsion consisting of polarized domains coexisting with paired atoms. The state was stabilized by low temperatures and strong interactions. Phys. Rev. A 101 , 013603 (2020).

Science•Jan 30, 2020•0 citations

Spin response and metastability of a strongly repulsive Fermi gas of ultracold atoms

Andrea Amico, Francesco Scazza, Giacomo Valtolina +6 more

Ultracold atomic Fermi gases close to Feshbach resonances represent the ideal platform to study strongly correlated fermionic states [1]. Up to now, most of the experimental efforts have been dedicated to the study of the famous BEC-BCS crossover, i.e. the transition from a Bose-Einstein condensate of tightly bound molecules to a BCS superfluid of long-range fermion pairs. However, such fermionic gases are the ideal environment to explore also the effects of strong, repulsive interactions. The interest in studying repulsive Fermi gases is manifold, since many phase transitions are driven by the strong repulsion between electrons in solids. One notable example is represented by the onset of itinerant ferromagnetism in metals, as envisioned by Stoner almost ninety years ago.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 1, 2017•0 citations

Correlation dynamics after short-pulse photoassociation

Christiane P. Koch, Ronnie Kosloff

Two atoms in an ultracold gas are correlated at short interatomic distances due to threshold effects in which the potential energy of their interaction dominates the kinetic energy. The correlations manifest themselves in a distinct nodal structure of the density matrix at short interatomic distances. Pump-probe spectroscopy has recently been suggested [Phys. Rev. Lett. 103, 260401 (2009)] to probe these pair correlations: A suitably chosen, short photoassociation laser pulse depletes the ground-state pair density within the photoassociation window, creating a nonstationary wave packet in the electronic ground state. The dynamics of this nonstationary wave packet is monitored by time-delayed probe and ionization pulses. Here we discuss how the choice of the pulse parameters affects the experimental feasibility of this pump-probe spectroscopy of two-body correlations.

arXiv:0904.2408•Physical Review A•Jun 28, 2010•10 citations

Nonzero-temperature dynamics of a repulsive two-component Fermi gas

Jarosław Ryszkiewicz, Mirosław Brewczyk, Tomasz Karpiuk

We study spin-dipole oscillations of a binary fermionic mixture at nonzero temperatures. We apply the atomic-orbital method combined with a Monte Carlo technique based sampling to probe finite temperatures. Our results agree quantitatively with a recent experiment [G. Valtolina et al., Nat. Phys. 13, 704 (2017)] showing the appearance of the ferromagnetic phase at stronger repulsion between components when the temperature is increased.

arXiv:1908.08367•Physical Review A•Jan 16, 2020•7 citations

Experiments on the ferromagnetic behavior of atomic repulsive Fermi gases

Andrea Amico

Ferromagnetism is a pure quantum correlation phenomenon, and yet it is responsible for most magnetic phenomena that we encounter in everyday life. Metallic magnets, such as iron and nickel, owe their magnetic behavior to mobile conduction electrons, whose spins can align with one another giving rise to non-zero magnetization. In the 1930s, Edmund C. Stoner first devised a simple and minimal model, where a ferromagnetic instability of the homogeneous Fermi gas is afforded only through short-range repulsive interactions. While his model captures the fundamental physics behind itinerant ferromagnetism, various additional effects in solid materials, such as orbital couplings and peculiar band dispersions, make it difficult to isolate the Stoner mechanism. Here we present our experimental investigation performed on an ultracold Fermi mixture of 6Li atoms where only genuine short-range repulsive interactions are present. Studying the stability of an artificially created ferromagnetic state, we provide a signature of a Stoner-like instability in a metastable system.

Il Nuovo Cimento C•Mar 1, 2017•0 citations
Physics
Pump-probe techniques, in which a short light pulse knocks the system out of equilibrium and another pulse is then used to monitor the dynamics, are commonplace in solid-state physics. Amico et al. used such a technique in a fermionic atomic gas to study what happens when the gas is plunged into a regime where the atoms strongly repel one another. The nature of this regime in an even mixture of two spin states has been debated—a ferromagnetic state was expected, but instead the atoms had a tendency to form pairs. Here, the researchers disentangled the two pathways and found that correlations consistent with ferromagnetism initially increased faster than the pairs formed, but neither clearly dominated over the other.
Phys. Rev. Lett. 121 , 253602 (2018).
We exploit a time-resolved pump-probe spectroscopic technique to study the out-of-equilibrium dynamics of an ultracold two-component Fermi gas, selectively quenched to strong repulsion along the upper branch of a broad Feshbach resonance. For critical interactions, we find the rapid growth of short-range anticorrelations between repulsive fermions to initially overcome concurrent pairing processes. At longer evolution times, these two competing mechanisms appear to macroscopically coexist in a short-range correlated state of fermions and pairs, unforeseen thus far. Our work provides fundamental insights into the fate of a repulsive Fermi gas, and offers new perspectives towards the exploration of complex dynamical regimes of fermionic matter.
Quantum Gases Ultracold atomic gases with strongly repulsive interactions can be a useful model system for studying the emergence of itinerant ferromagnetism. However, the same atoms that can order magnetically are also prone to pairing into loosely bound molecules. If an atomic system is suddenly placed in a strongly interacting regime, both processes occur and an inhomogeneous, phase-separated state consisting of unpaired and paired atoms can form. Scazza et al. studied this state with a variety of probes. The data were consistent with the formation of a quantum emulsion consisting of polarized domains coexisting with paired atoms. The state was stabilized by low temperatures and strong interactions. Phys. Rev. A 101 , 013603 (2020).
Ultracold atomic Fermi gases close to Feshbach resonances represent the ideal platform to study strongly correlated fermionic states [1]. Up to now, most of the experimental efforts have been dedicated to the study of the famous BEC-BCS crossover, i.e. the transition from a Bose-Einstein condensate of tightly bound molecules to a BCS superfluid of long-range fermion pairs. However, such fermionic gases are the ideal environment to explore also the effects of strong, repulsive interactions. The interest in studying repulsive Fermi gases is manifold, since many phase transitions are driven by the strong repulsion between electrons in solids. One notable example is represented by the onset of itinerant ferromagnetism in metals, as envisioned by Stoner almost ninety years ago.
Two atoms in an ultracold gas are correlated at short interatomic distances due to threshold effects in which the potential energy of their interaction dominates the kinetic energy. The correlations manifest themselves in a distinct nodal structure of the density matrix at short interatomic distances. Pump-probe spectroscopy has recently been suggested [Phys. Rev. Lett. 103, 260401 (2009)] to probe these pair correlations: A suitably chosen, short photoassociation laser pulse depletes the ground-state pair density within the photoassociation window, creating a nonstationary wave packet in the electronic ground state. The dynamics of this nonstationary wave packet is monitored by time-delayed probe and ionization pulses. Here we discuss how the choice of the pulse parameters affects the experimental feasibility of this pump-probe spectroscopy of two-body correlations.
Ferromagnetism is a pure quantum correlation phenomenon, and yet it is responsible for most magnetic phenomena that we encounter in everyday life. Metallic magnets, such as iron and nickel, owe their magnetic behavior to mobile conduction electrons, whose spins can align with one another giving rise to non-zero magnetization. In the 1930s, Edmund C. Stoner first devised a simple and minimal model, where a ferromagnetic instability of the homogeneous Fermi gas is afforded only through short-range repulsive interactions. While his model captures the fundamental physics behind itinerant ferromagnetism, various additional effects in solid materials, such as orbital couplings and peculiar band dispersions, make it difficult to isolate the Stoner mechanism. Here we present our experimental investigation performed on an ultracold Fermi mixture of 6Li atoms where only genuine short-range repulsive interactions are present. Studying the stability of an artificially created ferromagnetic state, we provide a signature of a Stoner-like instability in a metastable system.