ELFT HÍRADÓ

[tcsaba <tcsaba AT eik.bme.hu>]

                 M E G H Í V Ó - I N V I T A T I O N

    Seminar Series of the Department of Theoretical Physics at the
           Budapest University of Technology and Economics


                         Krisztián Palotás

                (Department of Complex Physical Systems,
           Institute of Physics, Slovak Academy of Sciences,
                      Bratislava, Slovakia
                               and
    MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group,
                 University of Szeged, Hungary)


 First-principles-based simulation of scanning tunneling microscopy:
         From magnetic surfaces to molecular structures

Understanding and engineering scanning tunneling microscopy (STM) image 
contrasts is of crucial importance in wide areas of surface science and 
related technologies, ranging from magnetic surfaces to molecular 
structures. Different STM tip effects on the image contrast are 
highlighted based on first principles calculations, going beyond the 
Tersoff-Hamann model, e.g., within 3D-WKB tunneling theory [1]. Examples 
include highly oriented pyrolytic graphite [2], which is commonly used 
for STM calibration, and complex surface magnetic structures exhibiting 
non-collinear magnetic order, like recently popular topologically 
protected skyrmions [3]. By comparing STM topographic data between 
experiment and large scale simulations, a statistical analysis of the 
tip apex structure is demonstrated for the first time [2]. A combination 
of STM and X-ray photodiffraction helps the understanding of chirality 
transfer from molecules to crystal surfaces [4]. Furthermore, two new 
developments of STM theories are presented: (i) an extension of Chen's 
derivative rule [5] for STM simulations including tip-orbital 
interference effects with demonstrated importance of such effects on the 
STM contrast for two surface structures: N-doped graphene and a magnetic 
Mn2H complex on the Ag(111) surface [6]; (ii) a combined tunneling 
charge and vector spin transport theory, which provides the first steps 
towards the theoretical modeling of high-resolution spin transfer torque 
imaging [3,7].

References:
[1] K. Palotás et al., Front. Phys. 9, 711 (2014)
[2] G. Mándi et al., J. Phys.: Condens. Matter 26, 485007 (2014), Prog. 
Surf. Sci. 90, 223 (2015)
[3] K. Palotás et al., Phys. Rev. B 96, 024410 (2017), arXiv:1801.08375 
(2018)
[4] W. Xiao et al., Nature Chem. 8, 326 (2016)
[5] C. J. Chen, Phys. Rev. B 42, 8841 (1990)
[6] G. Mándi, K. Palotás, Phys. Rev. B 91, 165406 (2015)
[7] K. Palotás et al., Phys. Rev. B 94, 064434 (2016)


Időpont: 2018. február 16. péntek, 10:15
Helyszín: BME Fizikai Intézet, Elméleti Fizika Tanszék,
Budafoki út 8. F-épület, III lépcsőház, szemináriumi szoba