Scanning tunneling microscopy: Recent challenges and future prospects

Speaker: Prof. Krisztian Palotas (Institute of Physics, Slovak Academy of Sciences)
Title: Scanning tunneling microscopy: Recent challenges and future prospects
Time: 10:00 AM, July 17th
Location: 909-B, Dushu Lake Campus
Scanning tunneling microscopy (STM) contributed considerably to the development of nanoscience and nanotechnology. In the talk some key aspects of electron tunneling theoretical models are pointed out, which have to be taken into account for proper interpretations of experimental STM images. An obvious example is the consideration of tip electron states going beyond the classical s-wave tip model of Tersoff and Hamann, which can dramatically affect the calculated STM contrasts [1]. In addition, the occurrence of tip orbital interference effects were recently highlighted, which can be quantified by revising the electron tunneling model of Chen [2]. Another challenge is how to measure vector quantities in scanning probe microscopies. The measurement of force vectors in atomic force microscopy (AFM) has recently been reported [3]. Considering spin-polarized STM (SP-STM), and the intrinsic charge and spin properties of the electron, a theory of combined tunneling charge and vector spin transport is presented [4], which allows the calculation of tunneling spin transport vector quantities, the longitudinal spin current and the spin transfer torque, in high spatial resolution on complex real-space spin textures, e.g. topologically protected skyrmions [5,6]. The possibility of obtaining local information on tunneling vector spin transport in SP-STM is expected to have a huge impact on new developing fields in spintronics. Finally, the emergence of topological magnetic objects on surfaces demands for methods for the unique identification of their topological properties, and SP-STM is proposed to fulfill this task [6,7].

1. G. Mándi, G. Teobaldi, K. Palotás, Prog. Surf. Sci. 90, 223 (2015).
2. G. Mándi, K. Palotás, Phys. Rev. B 91, 165406 (2015).
3. Y. Naitoh, R. Turansky, J. Brndiar, Y. J. Li, I. ?tich, Y. Sugawara, Nature Phys. 13, 663 (2017).
4. K. Palotás, G. Mándi, L. Szunyogh, Phys. Rev. B 94, 064434 (2016).
5. K. Palotás, L. Rózsa, L. Szunyogh, Phys. Rev. B 97, 174402 (2018).
6. K. Palotás, arXiv:1804.09096 (2018).
7. K. Palotás, L. Rózsa, E. Simon, L. Udvardi, L. Szunyogh, Phys. Rev. B 96, 024410 (2017).