Probing the Highly Correlated Mixed-Valent State via Charge Transfer with Atoms Moving Out from a Surface

Shao, Hongxiao; Nordlander, Peter; Langreth, David C.

doi:10.1103/physrevlett.77.948

Cited by 31 publications

(45 citation statements)

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“…III we present results in both the U → ∞ limit and in the physical finite-U case. The U → ∞ limit is studied for the purpose of comparing our 1/N results at N = 4 with previously published NCA results 6 . As a further test of the 1/N expansion we also present results extended down to the spinless N = 1 limit.…”

Section: Introductionmentioning

confidence: 94%

Room-temperature Kondo effect in atom-surface scattering: Dynamical1/Napproach

Merino

Marston

1998

Phys. Rev. B

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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 NCA approximation to solve the time-dependent Newns-Anderson Hamiltonian in the U → ∞ 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 U → ∞ limit with the NCA approximation 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 Ca ++ species can change the absolute scattered Ca + yields, the temperature dependence is qualitatively the same as that found in the U → ∞ 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.

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Section: Introductionmentioning

confidence: 94%

Room-temperature Kondo effect in atom-surface scattering: Dynamical1/Napproach

Merino

Marston

1998

Phys. Rev. B

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“…Shao et al [2] and Merino and Marston [3] had independently predicted that when a projectile ion has a single unpaired electron or hole, correlated electron behavior would induce either a Kondo resonance or mixed-valent state at the Fermi energy. The particular resonance formed would be a function of the projectile-surface distance, but the occupancy of the state and the subsequent neutralization rate in a scattering experiment would be a strong function of the surface temperature.…”

Section: Introductionmentioning

confidence: 98%

Measuring correlated-electron effects with low energy alkaline earth ion scattering

Yarmoff

2011

Nuclear Instruments and Methods in Physics Research Section B:

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“…On this time scale, the main contribution results from anisotropic phononmagnon interaction. To our knowledge, so far no theoretical study has been performed about the spin dynamics of transition metals on the femtosecond time scale, which is apparently needed.For the theoretical description of ultrafast nonequilibrium charge and spin dynamics, one can either rely on the Baym-Kadanoff-Keldysh Green's function approach [7] or employing an exact diagonalization framework. In this Letter, we prefer the latter method, which does not involve perturbation theory.…”

mentioning

confidence: 99%

“…For the theoretical description of ultrafast nonequilibrium charge and spin dynamics, one can either rely on the Baym-Kadanoff-Keldysh Green's function approach [7] or employing an exact diagonalization framework. In this Letter, we prefer the latter method, which does not involve perturbation theory.…”

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confidence: 99%

Ultrafast spin dynamics in nickel

Hübner

Zhang

1998

Phys. Rev. B

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The spin dynamics in Ni is studied by an exact diagonalization method on the ultrafast time scale. It is shown that the femtosecond relaxation of the magneto-optical response results from exchange interaction and spin-orbit coupling. Each of the two mechanisms affects the relaxation process differently. We find that the intrinsic spin dynamics occurs during about 10 fs while extrinsic effects such as laser-pulse duration and spectral width can slow down the observed dynamics considerably. Thus, our theory indicates that there is still room to accelerate the spin dynamics in experiments.PACS numbers: 75.40. Gb, 78.20.Ls, 78.47.+p The potential application of ferromagnetic materials on ultrafast time scales is attractive for information storage. Both experimentally and theoretically the ultrashort time behavior of spin dynamics in transition metals is a new and challenging area. Vaterlaus et al. [1] were the first to study the spin dynamics in ferromagnetic Gd. Employing spin-and time-resolved photo-emission with 60 ps probe pulses they found a spin-lattice relaxation (SLR) of 100±80 ps. Using femtosecond optical and magneto-optical pump-probe techniques, Beaurepaire et al [2] have studied the relaxation processes of electrons and spins in ferromagnetic Ni. They reported that the magnetization of a 22 nm thick film drops rapidly during the first picosecond and reaches its minimum after 2 ps. Recently, by time-resolved second harmonic generation (SHG), Hohlfeld et al. [3] found that even when electrons and lattice have not reached a common thermal equilibrium, the classical M (T ) curve can be reproduced for delay times longer than the electron thermalization time of about 280 fs. On the other hand, the transient magnetization reaches its minimum ≈ 50 fs before electron thermalization. Both groups used polycrystalline Ni but different pulse durations: 60 fs [2] vs 150 fs [3]. Recently even faster spin decays have been observed [4].At present, not even the mechanism for this ultrafast spin relaxation is known. Moreover, it is of great importance to know whether these results already reflect the intrinsic spin relaxation time scale or not. Theoretically, even the static ferromagnetism in transition metals has been a challenging topic as the electron correlation is very strong in these systems [5]. The theoretical treatment of the spin dynamics is limited. On the longer time scales, SLR been studied previously [6], and the theory yielded a relaxation time of 48 ps for Gd, in good agreement with the above mentioned experiment [1]. On this time scale, the main contribution results from anisotropic phononmagnon interaction. To our knowledge, so far no theoretical study has been performed about the spin dynamics of transition metals on the femtosecond time scale, which is apparently needed.For the theoretical description of ultrafast nonequilibrium charge and spin dynamics, one can either rely on the Baym-Kadanoff-Keldysh Green's function approach [7] or employing an exact diagonalization framework. In this Letter, we ...

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Probing the Highly Correlated Mixed-Valent State via Charge Transfer with Atoms Moving Out from a Surface

Cited by 31 publications

References 10 publications

Room-temperature Kondo effect in atom-surface scattering: Dynamical1/Napproach

Room-temperature Kondo effect in atom-surface scattering: Dynamical1/Napproach

Measuring correlated-electron effects with low energy alkaline earth ion scattering

Ultrafast spin dynamics in nickel

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