Symmetry aspects of spin filtering in molecular junctions: Hybridization and quantum interference effects

Dongzhe Li, Rajdeep Banerjee, Sourav Mondal, Ivan Maliyov, Mariya Romanova, Yannick J. Dappe, and Alexander Smogunov
Phys. Rev. B 99, 115403 – Published 5 March 2019
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Abstract

Control and manipulation of electric current and, especially, its degree of spin polarization (spin filtering) across single molecules are currently of great interest in the field of molecular spintronics. We explore one possible strategy based on the modification of nanojunction symmetry which can be realized, for example, by a mechanical strain. Such modification can activate new molecular orbitals which were inactive before due to their orbital mismatch with the electrode's conduction states. This can result in several important consequences such as (i) quantum interference effects appearing as Fano-like features in electron transmission and (ii) the change in molecular level hybridization with the electrode's states. We argue that the symmetry change can affect very differently two majority- and minority-spin conductances and thus alter significantly the resulting spin-filtering ratio as the junction symmetry is modified. We illustrate the idea for two basic molecular junctions: Ni/benzene/Ni (perpendicular vs tilted orientations) and Ni/Si chain/Ni (zigzag vs linear chains). In both cases, one highest occupied molecular orbital (HOMO) and one lowest unoccupied molecular orbital (LUMO) (out of HOMO and LUMO doublets) are important. In particular, their destructive interference with other orbitals leads to dramatic suppression of majority-spin conductance in low-symmetry configurations. For a minority-spin channel, on the contrary, the conductance is strongly enhanced when the symmetry is lowered due to an increase in hybridization strength. We believe that our results may offer a potential route for creating molecular devices with a large on-off ratio of spin polarization via quantum interference effects.

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  • Received 21 November 2018
  • Revised 12 February 2019

DOI:https://doi.org/10.1103/PhysRevB.99.115403

©2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Dongzhe Li1,*, Rajdeep Banerjee2, Sourav Mondal2, Ivan Maliyov3, Mariya Romanova4, Yannick J. Dappe5, and Alexander Smogunov5

  • 1Department of Physics, University of Konstanz, 78457 Konstanz, Germany
  • 2Theoretical Sciences Unit and School of Advanced Materials, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India
  • 3DEN, Service de Recherches en Métallurgie Physique, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette Cedex, France
  • 4Laboratoire des Solides Irradiés, Ecole Polytechnique, CEA-DRF-IRAMIS, CNRS UMR 7642, 91120 Palaiseau, France
  • 5SPEC, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France

  • *dongzhe.li@uni-konstanz.de

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Issue

Vol. 99, Iss. 11 — 15 March 2019

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