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Quantum Coherence Driven Magnetic Ordering in Biased Three Level Organometallic Molecules
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Novel understanding of the recent nanomagnet tailoring experiments and the possibility to further unveil the mechanisms by which the magnetic interactions arise in an atom by atom fashion covers importance as the demand for spin qubit and quantum state detection architectures increases. In the present letter, we address three spin states in triple quantum dots embedded in metallic tunneling junctions and show that the atom by atom magnetic interaction can be engineer through the electronic structure of the triple quantum dot, despite of not interacting among each other directly. We show that a bias and a gate voltage induces either a complete ferromagnetic state in the magnetic ion or a spin frustrated state with different stabilities, and switching among this states is possible on demand by electrical control. The role of quantum coherence in the triple dot is discussed with regards to the spin ordering as well as the interplay among electronic interference and induced dephasing by the metallic leads. This work sets foundations for more robust all electrically controlled spin architectures usable in quantum engineering systems and serves as a test bench for exploring unresolved questions in magnetic ordering and symmetry.  

National Category
Atom and Molecular Physics and Optics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-348659OAI: oai:DiVA.org:uu-348659DiVA, id: diva2:1198140
Available from: 2018-04-16 Created: 2018-04-16 Last updated: 2018-04-24
In thesis
1. Probing Magnetism at the Atomic Scale:  Non-Equilibrium Statistical Mechanics Theoretical Treatise
Open this publication in new window or tab >>Probing Magnetism at the Atomic Scale:  Non-Equilibrium Statistical Mechanics Theoretical Treatise
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Here, I present a theoretical study, based on non-equilibrium quantum statistical mechanics and on the non-equilibrium extension to the RKKY intveraction,where I investigate the emergence of magnetism at the atomic scale in adsorbed molecular complexes hosting localized spin moments, at the stake of being probed with scanning tunneling microscopy tip, and being driven by a temperature gradient and gated by an electric field. The scanning tunneling microscopy set up is modeled as a molecular junction with a magnetic molecule embedded within it, where the molecule consists in a set of electronic levels resembling the typical s-p orbitals of a metal hydride or an organometal, and a localized spin moment resembling the magnetic unit hosted by the latter and former type of molecules mentioned. The electronic levels and the magnetic units are coupled via the Kondo interaction. One of the electrodes in the junction plays the role of an scanning tunneling microscopy tip, and the other one, does it for the metal in which the molecule is adsorbed, and a bias voltage and a temperature gradient is applied across both metals, giving rise to the effect of the above mentioned experimental set up and producing electrical, spin, energy and heat currents as a response, providing the possibility to predict experimentally observed quantities such as differential conductivities. Throughout the thesis, I present first a comprehensive introduction to the topic pointing out its relevance, the experimental context in which the work I append lies and I as well present the formal structure of the work I present. The upcoming chapters, lead the audience to the discussion of the non-equilibrium formalism in atomic, molecular and condensed matter physics, paying special attention on the subject on magnetism, and putting in to context the molecular system where the interplay, among electrons, spins and phonons is relevant. To wrap up the theoretical discussion I described the state of the art progress on quantum coherence and interferometry in molecular junctions and locate my contribution into this context. Then I conclude and summarize. My contribution promises to pave the way to more robust spin based quantum engineered technology.

 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 205
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1678
Keywords
Non-Equilibrium Statistical Mechanics, Magnetism, Quantum Optics, Quantum Coherence, RKKY, Colciencias, Equation of Motion, Jauho-Meir-Wingreen Formalism
National Category
Atom and Molecular Physics and Optics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics; Physics with specialization in Quantum Chemistry; Physics and Astronomy specializing in Theoretical Physics
Identifiers
urn:nbn:se:uu:diva-349238 (URN)978-91-513-0353-6 (ISBN)
Public defence
2018-06-14, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 2, Uppsala, 13:31 (English)
Opponent
Supervisors
Available from: 2018-05-23 Created: 2018-04-24 Last updated: 2018-09-27

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