Polaronic effects in one-dimensional Fermi gas

Yingyi Zhang, Willie Ong, Ilya Arakelyan +1 more

S. Laalitya Uppalapati, Daniel E. Sheehy

Kazuya Nishimura, Eiji Nakano, Kei Iida +3 more

An impurity atom immersed in an ultracold atomic Fermi gas can form a quasiparticle, so-called Fermi polaron, due to impurity-fermion interaction. We consider a three-dimensional homogeneous dipolar Fermi gas as a medium, where the interatomic dipole-dipole interaction (DDI) makes the Fermi surface deformed into a spheroidal shape, and, using a Chevy-type variational method, investigate the ground-state properties of the Fermi polaron: the effective mass, the momentum distribution of a particle-hole excitation, the drag parameter, and the medium-density modification around the impurity. These quantities are shown to exhibit spatial anisotropies in such a way as to reflect the momentum anisotropy of the background dipolar Fermi gas. We also give numerical results for the polaron properties at the unitarity limit of the impurity-fermion interaction in the case in which the impurity and fermion masses are equal. It has been found that the transverse effective mass and the transverse momentum drag parameter of the polaron both tend to decrease by $\ensuremath{\sim}10%$ when the DDI strength is raised from 0 up to around its critical value, while the longitudinal ones exhibit a very weak dependence on the DDI.

Brandon Anderson, Chien‐Te Wu, Rufus Boyack +1 more

Austen Lamacraft

We consider the motion of a spin-1/2 impurity in a one-dimensional gas of spin-1/2 fermions. For antiferromagnetic interaction between the impurity and the fermions, the low temperature behavior of the system is governed by the two-channel Kondo effect, leading to the impurity becoming completely opaque to the spin excitations of the gas. As well as the known spectral signatures of the two-channel Kondo effect, we find that the low temperature mobility of the resulting "Kondo polaron" takes the universal form mu-->3variant Planck's over vF2/2pikB2T2, in sharp contrast to the spinless case where mu proportional variant T(-4).

M. J. Leskinen, O H T Nummi, Francesco Massel +1 more

We study a highly imbalanced Fermi gas in a one-dimensional (1D) optical lattice from the polaronic point of view. The time-evolving block decimation algorithm is used to calculate the ground state and dynamics of the system. We find polaronic behaviour qualitatively similar to that in the recent experiment by Schirotzek et al (2009 Phys. Rev. Lett. 102 230402), where radio-frequency (rf) spectroscopy was used to observe polarons in 3D space. In the weakly interacting limit, our exact results are in excellent agreement with a polaron ansatz, and in the strongly interacting limit, the results match with an approximative solution of the Bethe ansatz (BA), suggesting crossover from a quasiparticle to a charge-density excitation regime.