Transport measurement of the orbital Kondo effect with ultracold atoms

Abstract

The Kondo effect in condensed-matter systems manifests itself most sharply in their transport measurements. Here we propose an analogous transport signature of the orbital Kondo effect realized with ultracold atoms. Our system consists of imbalanced Fermi seas of two components of fermions and an impurity atom of different species which is confined by an isotropic potential. We first apply a \pi/2 pulse to transform two components of fermions into two superposition states. Their interactions with the impurity atom then cause a "transport" of fermions from majority to minority superposition states, whose numbers can be measured after applying another 3\pi/2 pulse. In particular, when the interaction of one component of fermions with the impurity atom is tuned close to a confinement-induced p-wave or higher partial-wave resonance, the resulting conductance is shown to exhibit the Kondo signature, i.e., universal logarithmic growth by lowering the temperature. The proposed transport measurement will thus provide a clear evidence of the orbital Kondo effect accessible in ultracold atom experiments and pave the way for developing new insights into Kondo physics.Comment: 7 pages; published versio

Antiferromagnetic interorbital spin-exchange interaction of Yb171

“…The competition between the magnetic correlation and localization effects is believed to induce rich quantum phases represented by a Doniach phase diagram [6]. Several schemes for cold-atom quantum simulation of the Kondo effect have been proposed for alkali atoms, which require superlattice structures [7] or a population of excited bands [8], and a confinement-induced p-wave resonance [9,10]. However, so far there have been no reports on the experimental progress of these proposals.…”

Time Evolution of the Kondo Resonance in Response to a Quench

“…In the latter, further progress hinges on an accurate non-perturbative solution for the nonequilibrium Green functions of an effective quantum impurity model. Such a solution, beyond allowing timeresolved spectroscopies of correlated lattice systems within DMFT to be addressed [43][44][45][46][47], would also be useful in understanding time-resolved scanning tunnelling microscopy of nanoscale systems [48] and proposed cold atom realizations of Kondo correlated states [49][50][51][52], which could be probed with real-time radio-frequency spectroscopy [53][54][55].In this Letter, we use the time-dependent numerical renormalization group (TDNRG) approach [56][57][58][59][60][61][62] to calculate the retarded two-time Green function, G(t 1 = t + t , t 2 = t), and associated spectral function, A(ω, t), of the Anderson impurity model in response to a quench at time t = 0, and apply this to investigate in detail the time evolution of the Kondo resonance. This topic has been addressed before within several approaches, including the non-crossing approximation [26,63], conserving approximations [64] and within CTQMC for quantum dots out of equilibrium [32].…”

“…In the latter, further progress hinges on an accurate non-perturbative solution for the nonequilibrium Green functions of an effective quantum impurity model. Such a solution, beyond allowing timeresolved spectroscopies of correlated lattice systems within DMFT to be addressed [43][44][45][46][47], would also be useful in understanding time-resolved scanning tunnelling microscopy of nanoscale systems [48] and proposed cold atom realizations of Kondo correlated states [49][50][51][52], which could be probed with real-time radio-frequency spectroscopy [53][54][55].…”

Production of a degenerate Fermi-Fermi mixture of dysprosium and potassium atoms

“…Fermionic mixtures made out of different atomic species additionally allow for the use of a species-selective optical lattices [29]. This handle opens the possibility in multicomponent systems for the realization of Kondo-related physics in transport measurements [30]. It should also be emphasized that two-component Fermi gases also offer a variety of interesting few-body effects such as atom-dimer resonant scattering [31,32] and confinement-induced Efimov resonances in systems with mixed dimensionality [33].…”