共查询到20条相似文献,搜索用时 15 毫秒
1.
Experiments on polarized fermion gases performed by trapping ultracold atoms in optical lattices allow the study of an attractive Hubbard model for which the strength of the on-site interaction is tuned by means of a Feshbach resonance. Using a well-known particle-hole transformation we discuss how results obtained for this system can be reinterpreted in the context of a doped repulsive Hubbard model. In particular, we show that the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state corresponds to the striped state of the two-dimensional doped positive U Hubbard model. We then use the results of numerical studies of the striped state to relate the periodicity of the FFLO state to the spin polarization. We also comment on the relationship of the d(x(2)-y(2)) superconducting phase of the doped 2D repulsive Hubbard model to a d-wave spin density wave state for the attractive case. 相似文献
2.
J. Kajala F. Massel P. Törmä 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,65(1-2):91-98
In this work we analyze the dynamical behavior of the collision between two clouds of fermionic atoms with opposite spin polarization. By means of the time-evolving block decimation (TEBD) numerical method, we simulate the collision of two one-dimensional clouds in a lattice. There is a symmetry in the collision behaviour between the attractive and repulsive interactions. We analyze the pair formation dynamics in the collision region, providing a quantitative analysis of the pair formation mechanism in terms of a simple two-site model. 相似文献
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Mullin WJ 《Physical review letters》1986,57(21):2710-2713
6.
I. A. Fomin 《JETP Letters》1997,65(9):749-754
A microscopic derivation of the equations of transverse spin dynamics of a spin-polarized Fermi liquid at zero temperature
is given in the leading-order approximation in the frequencies and wave vectors characterizing the spin motion. The equations
are applicable for arbitrary degree of polarization and arbitrary deviations of the spin direction from the equilibrium orientation.
The solutions describing a coherently precessing two-domain structure and spin waves are examined. In contrast to the assertion
discussed in the literature that spin waves are damped at zero temperature, spin waves are found to be undamped in the long-wavelength
limit.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 9, 717–721 (10 May 1997) 相似文献
7.
P. Massignan G. M. Bruun 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,65(1-2):83-89
We analyze the properties of a single impurity immersed in a Fermi sea. At positive energy and scattering lengths, we show that the system possesses a well-defined but metastable excitation, the repulsive polaron, and we calculate its energy, quasiparticle residue and effective mass. From a thermodynamic argument we obtain the number of particles in the dressing cloud, illustrating the repulsive character of the polaron. Identifying the important 2- and 3-body decay channels, we furthermore calculate the lifetime of the repulsive polaron. The stability conditions for the formation of fully spin polarized (ferromagnetic) domains are then examined for a binary mixture of atoms with a general mass ratio. Our results indicate that mass imbalance lowers the critical interaction strength for phase-separation, but that very short quasiparticle decay times will complicate the experimental observation of itinerant ferromagnetism. Finally, we present the spectral function of the impurity for various coupling strengths and momenta. 相似文献
8.
T. L. Andreeva 《Journal of Experimental and Theoretical Physics》2017,124(2):193-195
The spin dynamics of cold polarized gases are investigated using the Boltzmann equation. The dispersion relation for spin waves (transverse component of the magnetic moment) and the spin diffusion coefficient of the longitudinal component of the magnetic moment are calculated without using fitting parameters. The spin wave frequency and the diffusion coefficient for rubidium atoms are estimated numerically. 相似文献
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J. Koster 《Physics of Particles and Nuclei》2014,45(1):88-90
The PHENIX experiment probes the transverse spin structure of the proton with asymmetries of particle production in polarized proton collisions. This talk summarizes the measurements of A N in hadron production at forward and at mid rapidities. 相似文献
11.
Orso G 《Physical review letters》2007,98(7):070402
We investigate two-component attractive Fermi gases with imbalanced spin populations in trapped one-dimensional configurations. The ground state properties are determined with the local density approximation, starting from the exact Bethe-ansatz equations for the homogeneous case. We predict that the atoms are distributed according to a two-shell structure: a partially polarized phase in the center of the trap and either a fully paired or a fully polarized phase in the wings. The partially polarized core is expected to be a superfluid of the Fulde-Ferrell-Larkin-Ovchinnikov type. The size of the cloud as well as the critical spin polarization needed to suppress the fully paired shell are calculated as a function of the coupling strength. 相似文献
12.
We consider a highly polarized Fermi gas with a single ↓ atom within a Fermi sea of ↑ atoms. We extend a preceding many-body
analysis to the case where a bound state is formed between the ↓ atom and an ↑ atom. 相似文献
13.
We consider a single atom within a Fermi sea of atoms. We elucidate by a full many-body analysis the quite mysterious agreement between Monte Carlo results and approximate calculations taking only into account single particle-hole excitations. It results from a nearly perfect destructive interference of the contributions of states with more than one particle-hole pair. This is linked to the remarkable efficiency of the expansion in powers of hole wave vectors, the lowest order leading to perfect interference. Going up to two particle-hole pairs gives an essentially perfect agreement with known exact results. Hence our treatment amounts to an exact solution of this problem. 相似文献
14.
Tilman Enss 《The European physical journal. Special topics》2013,217(1):169-175
Fermi gases with short-range interactions are ubiquitous in ultracold atomic systems. In the absence of spin-flipping processes the number of atoms in each spin species is conserved separately, and we discuss the associated Ward identities. For contact interactions the spin conductivity spectral function σs(ω) has universal power-law tails at high frequency. We derive the spin f-sum rule and show that it is not affected by these tails in d < 4 dimensions. Likewise the shear viscosity spectral function η(ω) has universal tails; in contrast they modify the viscosity sum rule in a characteristic way. 相似文献
15.
We present a full many-body analysis of the problem of a single ↓ atom resonantly interacting with a Fermi sea of ↑ atoms. A series of successive approximations permits us to clarify the quite mysterious agreement between Monte Carlo results and approximate calculations taking only into account single particle-hole excitations. We show that it results from a nearly perfect destructive interference of the contributions of states with more than one particle-hole pair. Our treatment provides, at the same time, an essentially exact solution to this problem. 相似文献
16.
Liao YA Revelle M Paprotta T Rittner AS Li W Partridge GB Hulet RG 《Physical review letters》2011,107(14):145305
We study the role of particle transport and evaporation on the phase separation of an ultracold, spin-polarized atomic Fermi gas. We show that the previously observed deformation of the superfluid paired core is a result of evaporative depolarization of the superfluid due to a combination of enhanced evaporation at the center of the trap and the inhibition of spin transport at the normal-superfluid phase boundary. These factors contribute to a nonequilibrium jump in the chemical potentials at the phase boundary. Once formed, the deformed state is highly metastable, persisting for times of up to 2?s. 相似文献
17.
We examine the collisional behavior of two-component Fermi gases released at zero temperature from a harmonic trap. Using a phase-space formalism to calculate the collision rate during expansion, we find that Pauli blocking plays only a minor role for momentum changing collisions. As a result, for a large scattering cross section, Pauli blocking will not prevent the gas from entering the collisionally hydrodynamic regime. In contrast to the bosonic case, hydrodynamic expansion at very low temperatures is therefore not evidence for fermionic superfluidity. 相似文献
18.
We investigate a two-species Fermi gas in which one species is confined in a two-dimensional plane (2D) or one-dimensional line (1D) while the other is free in the three-dimensional space (3D). We discuss the realization of such a system with the interspecies interaction tuned to resonance. When the mass ratio is in the range 0.0351相似文献
19.
X. S. Yang B. B. Huang S. L. Wan 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(4):445-450
We investigate a mix-dimensional Fermi-Fermi mixtures in which one species is confined
in two-dimensional (2D) space while the other is free in three-dimensional space (3D). We
determine the superfluid transition temperature
T
c
for the entire BCS-BEC crossover
including the important effects of noncondensed pairs. We find that the transition
temperature reduces while the imbalance of mass is increased or lattice spacing is
reduced. In spin imbalance case, the stability of superfluid is sharply destroyed by
increasing the polarization. 相似文献
20.
Evaporative cooling was performed to cool fermionic 173Yb atoms in a crossed optical dipole trap. The large elastic collision rate leads to efficient evaporation and we have successfully cooled the atoms to 0.37+/-0.06 of the Fermi temperature, that is to say, to a quantum degenerate regime. In this regime, a plunge of evaporation efficiency was observed as a result of Fermi degeneracy. 相似文献