Using a recently developd many-body theory, we investigate the velocity dependence of charge transfer in atom-surface scattering. We show that under certain conditions, intra-atomic correlation effects can introduce nontrivial sources of nonadiabaticity. For situations where a sharp Kondo resonance is formed near the Fermi energy, the system can exhibit strong nonadiabatic effects even at low velocities. This nonadiabatic behavior is caused by the relatively long-time scale for the formation or survival of the Kondo peak.
The Kondo effect may be observable in some atom-surface scattering experiments, in particular, those involving alkaline-earth atoms. By combining Keldysh techniques with the noncrossing (NCA) approximation to solve the time-dependent Newns-Anderson Hamiltonian in the $\stackrel{\ensuremath{\rightarrow}}{U}\ensuremath{\infty}$ limit, Shao, Nordlander, and Langreth found an anomalously strong surface-temperature dependence of the outgoing charge state fractions. Here we employ a dynamical
1/N expansion with a finite Coulomb interaction
U to give a more realistic description of the scattering process. We test the accuracy of the
1/N expansion in the
N=1 case of spinless fermions against the exact independent particle solution. We then compare results obtained in the $\stackrel{\ensuremath{\rightarrow}}{U}\ensuremath{\infty}$ limit with the NCA at
N=4 and recover qualitative features already found. Finally, we analyze the realistic situation of Ca atoms with
U=5.8 eV scattered off Cu(001) surfaces. Although the presence of the doubly ionized
Ca2+ species can change the absolute scattered
Ca+ yields, the temperature dependence is qualitatively the same as that found in the $\stackrel{\ensuremath{\rightarrow}}{U}\ensuremath{\infty}$ limit. One of the main difficulties that experimentalists face in attempting to detect this effect is that the atomic velocity must be kept small enough to limit kinematic smearing of the Fermi surface of the metal.
The wave function of an atom passed through a diffraction grating acquires a regular space structure and the interaction of another particle with this atom can be thought of as scattering on a 'quantum grating' composed of a single atom. Probing this 'grating' by collisions with charged projectiles reveals interference effects due to coherent contributions of its 'slits' to the transition amplitude. In particular, the spectra of electrons emitted from the atom in collisions with swift ions exhibit a pronounced interference pattern whose shape can be extremely sensitive to the collision velocity.
We propose a simple but novel scheme to realize the Kondo effect with ultracold atoms. Our system consists of a Fermi sea of spinless fermions interacting with an impurity atom of different species which is confined by an isotropic potential. The interspecies attraction can be tuned with an s-wave Feshbach resonance so that the impurity atom and a spinless fermion form a bound dimer that occupies a threefold-degenerate p orbital of the confinement potential. Many-body scatterings of this dimer and surrounding spinless fermions occur with exchanging their angular momenta and thus exhibit the SU(3) orbital Kondo effect. The associated Kondo temperature has a universal leading exponent given by TK∝exp[-π/(3apkF3)] that depends only on an effective p-wave scattering volume ap and a Fermi wave vector kF. We also elucidate a Kondo singlet formation at zero temperature and an anisotropic interdimer interaction mediated by surrounding spinless fermions. The Kondo effect thus realized in ultracold atom experiments may be observed as an increasing atom loss by lowering the temperature or with radio-frequency spectroscopy. Our scheme and its extension to a dense Kondo lattice will be useful to develop new insights into yet unresolved aspects of Kondo physics.
We propose an experimental protocol to directly observe the Kondo effect by scattering ultracold atoms. We propose using an optical Feshbach resonance to engineer Kondo-type spin-dependent interactions in a system with ultracold
6Li and
87Rb gases. We calculate the momentum transferred from the
87Rb gas to the
6Li gas in a scattering experiment and show that it has a logarithmically enhanced temperature dependence, characteristic of the Kondo effect, and analogous to the resistivity of alloys with magnetic impurities. Experimentally detecting this enhancement will give a different perspective on the Kondo effect, and allow us to explore a rich variety of problems such as the Kondo lattice problem and heavy-fermion systems.