Giant Spin Oscillations in an Ultracold Fermi Sea

Krauser, J.; Ebling, Ulrich; Fläschner, Nick; Heinze, Jannes; Sengstock, K.; Lewenstein, Maciej; Eckardt, André; Becker, Christoph

doi:10.1126/science.1244059

Cited by 57 publications

(87 citation statements)

References 37 publications

(35 reference statements)

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“…Additionally, at very low temperatures, Pauli blocking can partially prevent mode changing collisions for a spinpolarized sample, as recently observed in Ref. [66]. However, even in a spin-polarized gas, spin-and mode-changing processes may occur, resulting in a doubly occupied mode.…”

Section: The Generalized Spin Model Approximation: Validity and Discusupporting

confidence: 55%

Dynamics of Interacting Fermions in Spin-Dependent Potentials

Koller¹,

Wall²,

Mundinger³

et al. 2016

Phys. Rev. Lett.

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Recent experiments with dilute trapped Fermi gases observed that weak interactions can drastically modify spin transport dynamics and give rise to robust collective effects including global demagnetization, macroscopic spin waves, spin segregation, and spin self-rephasing. In this work we develop a framework for studying the dynamics of weakly interacting fermionic gases following a spin-dependent change of the trapping potential which illuminates the interplay between spin, motion, Fermi statistics, and interactions. The key idea is the projection of the state of the system onto a set of lattice spin models defined on the single-particle mode space. Collective phenomena, including the global spreading of quantum correlations in real space, arise as a consequence of the long-ranged character of the spin model couplings. This approach achieves good agreement with prior measurements and suggests a number of directions for future experiments.The interplay between spin and motional degrees of freedom in interacting electron systems has been a longstanding research topic in condensed matter physics. Interactions can modify the behavior of individual electrons and give rise to emergent collective phenomena such as superconductivity and colossal magnetoresistance [1]. Theoretical understanding of non-equilibrium dynamics in interacting fermionic matter is limited, however, and many open questions remain. Ultracold atomic Fermi gases, with precisely controllable parameters, offer an outstanding opportunity to investigate the emergence of collective behavior in out-of-equilibrium settings.Progress in this direction has been made in recent experiments with ultracold spin-1/2 fermionic vapors, where initially spin-polarized gases were subjected to a spin-dependent trapping potential ( Fig. 1) implemented by a magnetic field gradient [2-4], or a spin-dependent harmonic trapping frequency [5-8] -equivalent to a spatially-varying gradient. Even in the weakly interacting regime, drastic modifications of the single-particle dynamics were reported. Moreover, despite the local character of the interactions, collective phenomena were observed, including demagnetization and transverse spinwaves in the former, and a time-dependent separation (segregation) of the spin densities and spin self-rephasing in the latter. Although mean-field and kinetic theory formulations have explained some of these phenomena [8][9][10][11][12][13][14][15][16][17][18], a theory capable of describing all the time scales and the interplay between spin, motion, and interactions has not been developed.In this work, we develop a framework that accounts for the coupling of spin and motion in weakly interacting Fermi gases. We qualitatively reproduce and explain all phenomena of the aforementioned experiments and obtain quantitative agreement with the results of Ref. [7]. In this formulation the state of the system is represented as a superposition of spin configurations which live on lattices whose sites correspond to modes of the underlying single-particle sy...

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Section: The Generalized Spin Model Approximation: Validity and Discusupporting

confidence: 55%

Dynamics of Interacting Fermions in Spin-Dependent Potentials

Koller¹,

Wall²,

Mundinger³

et al. 2016

Phys. Rev. Lett.

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“…Actually, the experimental setup for spin dynamics in LSFG33343536 can be shared to examine the results in this work. The system can be initially prepared with a balanced spin mixture with , which is confined in a harmonic trap, and evaporated to a temperature .…”

Section: Resultsmentioning

confidence: 99%

“…Recently, considerable effort has been devoted to the spin dynamics33343536 and Mott-insulator transformation3738 in the LSFG. To our best knowledge, however, the study related to FM transition in LSFG is rare.…”

mentioning

confidence: 99%

Spontaneous separation of large-spin Fermi gas in the harmonic trap: a density functional study

Sun

2016

Sci Rep

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The component separation of the trapped large-spin Fermi gas is studied within density functional theory. The ground state and ferromagnetic transition in the gas, with and without the spin mixing collision, are calculated. In the absence of spin mixing, two patterns of separation are observed as the interaction between atoms increases, whereas only one of them corresponds to a ferromagnetic transition. The phase diagram suggests that the pattern which the system chooses depends on the interaction strength in the collision channels. With the presence of spin mixing, the distribution of phase region changes because of the interplay between different collision channels. Specifically, the spin exchange benefits the FM transition, while it suppresses the component separation of CS-II pattern.

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“…The direct observation of several periods of these oscillations has allowed us to demonstrate the coherence of the process and to measure the exchange interaction strength in an accurate, model-independent way. We note that, if compared with the spin dynamics observed in other atomic systems, arising from either small differences in the scattering lengths [23][24][25] or from second-order tunneling between adjacent sites of an optical lattice [26], the oscillation that we have measured is significantly fast. In particular, the exchange energy V ex , on the order of ∼h × 10 kHz, is much larger than either the Fermi (k B T F ) or the thermal (k B T) energy, which makes 173 Yb remarkably interesting for the observation of quantum magnetism in a two-orbital system with SUðNÞ interaction symmetry [4].…”

Section: -3mentioning

confidence: 90%

Observing the Great Spin and Orbital Swap

Rey¹

2014

Physics

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Giant Spin Oscillations in an Ultracold Fermi Sea

Cited by 57 publications

References 37 publications

Dynamics of Interacting Fermions in Spin-Dependent Potentials

Dynamics of Interacting Fermions in Spin-Dependent Potentials

Spontaneous separation of large-spin Fermi gas in the harmonic trap: a density functional study

Observing the Great Spin and Orbital Swap

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