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Research Seminar of Dr. Wei WU from University College London
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Research Seminar of Dr. Wei WU from University College London

Lecture Time: 09:30 on 28th June, 2016

Lecture Room: C501 of National Science Park

Lecture Title: Theoretical Modelling of Electronic Structure and Exchange Interactions in Metal-Phthalocyanines

Wei WU

Department of Materials and London Centre for Nanotechnology, Imperial College London1, UCL Department of Physics and Astronomy and London Centre for Nanotechnology, University College London2, Department of Chemistry, Imperial College3

Abstract

Organic magnets have recently attracted much attention owing to their chemical processibility, structural flexibility, and long spin-lattice relaxation time. Understanding exchange interaction in organic magnets provides a key foundation for quantum molecular magnetism, molecular spintronics, and quantum information processing [1-3]. We have systematically performed first-principles calculations using density functional theory for a range of chain geometries in lithium- (spin-1/2), cobalt- (spin-1/2), chromium- (spin-2), and copper (spin-1/2)-Pc molecular chains [1-2, 4-8]. In LiPc, we found spin density wave phase that could explain the previous experimental results, and a large exchange interaction up to 1000 K [6]. A combination of experiments and theoretical calculations has shown that in CoPc there is a high magnetic transition temperature well above the boiling point of liquid Nitrogen [7,8]. This large anti-ferromagnetic interaction, which is due to the out-of-plane orbital dz2, could be useful for spintronics and quantum information process. We have also assessed the potential of CrPc (spin-2) to test the Haldane’s conjecture of the spin excitation gap in the integer-spin chain [9].

Our calculations have not only rationalized the related experimental results, but also provided important guidance for the fabrication of spintronic materials with high-transition temperature and predicted interesting physics in these organic low dimensional strongly correlated systems.
References:
[1] S. Heutz, et. al., Adv. Mat., 19, 3618 (2007)
[2] Hai Wang, et. al., ACS Nano, 4, 3921 (2010)
[3] M. Warner, et. al., Nature, 503, 504 (2013)
[4] Wei Wu, et. al., Phys. Rev. B 77, 184403 (2008)
[5] Wei Wu, et. al., Phys. Rev. B 84, 024427 (2011)
[6] Wei Wu, et. al., Phys. Rev. B 88, 180404 (2013)
[7] Wei Wu, et. al., Phys. Rev. B 88, 024426 (2013)

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