Research Seminar of Dr. Wei WU fromUniversity 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)