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Workshops

Functional Molecules on Surfaces: New Building Blocks for Nano-spintronics

October 2, 2012 to October 4, 2012
Location : Gustav-Stresemann-Institut, Bonn, Germany

Organisers

  • Valerio Bellini (CNR- Institute of Nanoscience, Modena, Italy)
  • Nicolae Atodiresei (Peter Grünberg Institute and Research Center Julich Institute for Advanced Simulation, Germany)
  • Paolo Ferriani ( University of Kiel, Germany)
  • Stefan Blügel (Forschungszentrum Jülich, Germany)

Supports

   CECAM

   Psi-k

Description

Spin-dependent effects and interactions play a very significant role in current research in nanoscience. The study of the electron spin degrees of freedom at the molecular scale has conveyed an increasing attention both from fundamental and technological points of view. Much effort is devoted nowadays to the integration of novel functional metalorganic molecules with tailored electronic and magnetic properties into traditional solid-state nano-electronic devices. 
Such a integration faces several major challenges. First, the molecules must be addressable by external stimuli in order to function as working molecular spintronic devices. Second, to be technologically appealing, the molecules must be organized on solid surfaces or wired to metal electrodes in a controlled fashion.  Third, scanning probe microscopy techniques, which are key experimental tools due to their capability to address and manipulate molecules individually, require comparison with reliable electronic structure calculations for an unambiguous interpretation and understanding of their experimental data.
The theoretical characterization of the above issues is clearly a fundamental step that the scientific community is challenged with. A correct description of the complex atomic, electronic, and magnetic structure, their energy barriers and the response to external stimuli of the systems requires the use of accurate, yet feasible from the computational point of view, methodologies, which represent a real challenge for today’s theoretical, simulation and computational research. 
This Workshop represents a novel and timely effort that aims to bring together leading theoretical scientists working in the above fields and meets the urge to integrate more tightly the computational chemistry and computational physics communities, historically prone to tackle different, and from time to time divergent, research pathways. Few key experimentalists involved in the synthesis of novel functional magnetic molecules and in the study of molecule-surface systems by scanning probe and synchrotron radiation experiments have been also invited, in order to set the stage and frame of challenges.

To apply to this workshop and for more information please visit our official webpage:

http://www.fz-juelich.de/pgi/FunMol

 

Important dates:

Deadline for registration, abstract submission and accomodation reservation postponed to: Sunday 15th July 2012 

 

Quantum computing, ultra-high density magnetic storage, and spintronics are some of the most promising research areas that could lead to major technological breakthroughs [1,2]. Functional magnetic molecules play a key role in these fields since they provide tunable nanometer-size magnetic units, which is an essential requirement for constructing new devices. The occurrence of magnetic hysteresis at the molecular level, due to the quantum phenomenon of slow magnetic relaxation in high-spin single molecule magnets (SMM) [3] has raised a tremendous scientific interest and has suggested some revolutionary applications [4,5]. Recently, an increasing number of molecules has been successfully sublimated or dry-imprinted in ultra-high vacuum conditions. Among them, a dominant role has been attained by the very robust family of monometallic porphyrins, phthalocyanines, and rare-earth double deckers [6]; lately complex poly-metallic molecules as Fe4 [7] and Cr-base molecular rings [8,9] have been also deposited by liquid phase or under UHV on Au(111) surfaces.

Density-functional methods have played a crucial role in the characterization of molecules in the gas phase and of molecule-surface systems. The emphasis has been placed on different issues, such as the extraction of the magnetic exchange and spin interaction parameters in polymetallic magnetic molecules by total energy calculations [10,11], the influence that structural rearrangement or chemical modification have on electronic, magnetic and transport properties [12], or the development of advanced theoretical methodologies in order to properly account for the molecule-surface interaction. 

The efforts made in the last few years brought to important advances in this field. First of all, van der Waals dispersion interactions, the inclusion of which is indispensable to correctly characterize adsorption energies and geometries of molecules on surface, have been taken into account from first principles [13] or by means of simplified parameterizations [14]. Secondly, in order to assess correctly charge-transfer, work-function modifications, molecular orbitals–surface levels alignment and transport across molecule-surface interfaces, methods to correct the incomplete self-interaction cancellation and, in general, account for the electronic correlations beyond local density exchange-correlation functionals have been considered. The use of optimized effective potentials, Hubbard on-site terms, and hybrid functionals, or of the GW approximation are some of the possible approaches towards solutions to these problems [15-19]. 

Simulations of scanning tunneling microscopy and spectroscopy experiments have demonstrated to be essential for the correct assessment of what is actually measured in experiments on molecules [20]. They provide as well a benchmark validating the computational results and theoretical approximations. Finally, in the transport regime, functional molecules might lead to unique spin filtering capabilities [21] or tunable (with structural, electric, magnetic or radiative stimuli) conducting channels [22], and are candidates themselves as future building blocks for electronic nano-devices [23].

Spin-dependent effects and interactions play a very significant role in current research in nanoscience. The study of the electron spin degrees of freedom at the molecular scale has conveyed an increasing attention both from fundamental and technological points of view. Much effort is devoted nowadays to the integration of novel functional metalorganic molecules with tailored electronic and magnetic properties into traditional solid-state nano-electronic devices. Such a integration faces several major challenges. First, the molecules must be addressable by external stimuli in order to function as working molecular spintronic devices. Second, to be technologically appealing, the molecules must be organized on solid surfaces or wired to metal electrodes in a controlled fashion.  Third, scanning probe microscopy techniques, which are key experimental tools due to their capability to address and manipulate molecules individually, require comparison with reliable electronic structure calculations for an unambiguous interpretation and understanding of their experimental data. The theoretical characterization of the above issues is clearly a fundamental step that the scientific community is challenged with. A correct description of the complex atomic, electronic, and magnetic structure, their energy barriers and the response to external stimuli of the systems requires the use of accurate, yet feasible from the computational point of view, methodologies, which represent a real challenge for today’s theoretical, simulation and computational research.

This Workshop represents a novel and timely effort that aims to bring together leading theoretical scientists working in the above fields and meets the urge to integrate more tightly the computational chemistry and computational physics communities, historically prone to tackle different, and from time to time divergent, research pathways. Few key experimentalists involved in the synthesis of novel functional magnetic molecules and in the study of molecule-surface systems by scanning probe and synchrotron radiation experiments have been also invited, in order to set the stage and frame of challenges.

References

[1] A. Cornia, et al., in: R. Winpenny (Ed.), “Single-molecule magnets and related phenomena”, Structure & Bonding Book Series, vol. 122, Springer, Berlin, Heidelberg, 2006, p. 133.
[2] M. Affronte, et al., “A ring cycle: studies of heterometallic wheels”, Chem. Commun. 18, 1789 (2007).
[3] R. Sessoli, et al., “Magnetic bistability in a metal-ion cluster”, Nature 365, 141 (1993).
[4] M.N. Leuenberger and D. Loss, “Quantum computing in molecular magnets”, Nature 410, 789 (2001).
[5] L. Bogani and W. Wernsdorfer, “Molecular spintronics using single-molecule magnets”, Nature Mater. 7, 179 (2008).
[6] L. Vitali, et al., “Electronic Structure of Surface-supported Bis(phthalocyaninato) terbium(III) Single Molecular Magnets”, Nano Lett. 8, 3364 (2008).
[7] M. Mannini, et al., “Magnetic memory of a single-molecule quantum magnet wired to a gold surface”, Nat. Mater. 8, 194 (2009).
[8] M. Rancan et al., “Chromium wheels quasi-hexagonal 2D assembling by direct UHV sublimation”, Chem. Commun. 47, 5744 (2011).
[9] V. Corradini et al., “Successful grafting of isolated molecular Cr7Ni rings on Au(111) surface”, Phys. Rev. B 79, 144419, (2009).
[10] F. Neese, “Prediction of Molecular Spectra and Molecular Properties with Density Functional Theory: from Fundamental Theory to Exchange Coupling”, Coord. Chem. Rev., 253, 526 (2009).
[11] V. Bellini et al. “Propagation of spin information at supra-molecular scale through hetero-aromatic linkers”, Phys. Rev. Lett. 106, 227205 (2011).
[12] Zhao et al., “Controlling the Kondo Effect of an Adsorbed Magnetic Ion Through Its Chemical Bonding”, Science 309, 1542 (2005).
[13] Chakarova-Käck et al., “Binding of polycyclic aromatic hydrocarbons and graphene dimers in density functional theory”, New. J. Phys. 12, 013017 (2010).
[14] S. Grimme, “Semiempirical GGA-Type Density Functional Constructed with a Long-Range Dispersion Correction”, J. Comput. Chem. 27, 1787, (2006).
[15] F. Della Sala, et al., “The Role of Exact-Exchange in the Theoretical Description of Organic-Metal Interfaces”, Int. J. Quantum Chem. 110, 2162 (2010).
[16] M. Bernien, et al., “Tailoring the Nature of Magnetic Coupling of Fe-Porphyrin Molecules to Ferromagnetic Substrates”, Phys. Rev. Lett. 102, 047202 (2009).
[17] E. Ruiz, “Magnetic Communication through Functionalized Nanotubes: A Theoretical Study”, Nano Lett. 6, 380, (2006).
[18] J. B. Neaton, et al., “Renormalization of molecular electronic levels at metal-molecule interfaces”, Phys. Rev. Letters 97, 216405, (2006).
[19] K. S. Thygesen, “Impact of exchange-correlation effects on the IV characteristics of a molecular junction”, Phys. Rev. Lett. 100, 166804 (2008).
[20] N. Atodiresei, et al, “Design of the Local Spin Polarization at the Organic-Ferromagnetic Interface”, Phys. Rev. Lett. 105, 066601 (2010).
[21] K. Park, et al., “Effects of bonding type and interface geometry on coherent transport through the single-molecule magnet Mn12”, Phys. Rev. B 81, 125447 (2010).
[22] W. Y. Kim et al., “Tuning Molecular Orbitals in Molecular Electronics and Spintronics”, Acc. Chem Res. 43, 111 (2010).
[23] A.R. Rocha, et al., “Towards molecular spintronics”, Nat. Mater. 4, 335 (2005).