Transport through artificial single-molecule magnets: Spin-pair state sequential tunneling and Kondo effects |
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Authors: | Niu Peng-Bin Wang Qiang Nie Yi-Hang |
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Institution: | Institute of Theoretical Physics and Department of Physics, Shanxi University, Taiyuan 030006, China |
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Abstract: | The transport properties of an artificial single-molecule magnet based on a CdTe quantum dot doped with a single Mn+2 ion (S=5/2) are investigated by the non-equilibrium Green function method. We consider a minimal model where the Mn-hole exchange coupling is strongly anisotropic so that spin-flip is suppressed and the impurity spin S and a hole spin s entering quantum dot are coupled into spin pair states with (2S+1) sublevels. In the sequential tunneling regime, the differential conductance exhibits (2S+1) possible peaks, corresponding to resonance tunneling via (2S+1) sublevels. At low temperature, Kondo physics dominates transport and (2S+1) Kondo peaks occur in the local density of states and conductance. These peaks originate from the spin-singlet state formed by the holes in the leads and on the dot via higher-order processes and are related to the parallel and antiparallel spin pair states. |
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Keywords: | artificial single-molecule magnet Hubbard Green function spin-pair Kondo effect |
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