Fyzikální ústav Akademie věd ČR

Semináře

Úterý, 02.05.2017 14:00 - 15:30

Tomáš Rauch (MLU, Halle-Wittenberg, SRN)

Quantum wells of HgTe crystallizing in the zincblende lattice were the first systems in which signatures of quantum spin Hall effect were observed in two dimensions. In three dimensions, α-Sn was one of the first materials proposed to be a time-reversal invariant strong topological insulator. Here I will present the results of our calculations of topological properties of these zincblende and diamond materials in three dimensions. We were able to calculate various topological invariants of electronic bulk bands and thus prove the existence of different insulating and metallic topological phases, mostly mediated by strain or alloying. Our findings were confirmed by calculating the electronic structure of semi-infinite systems.

Úterý, 16.05.2017 10:00 - 11:00

Jindřich Kolorenč (Fyzikální ústav AV ČR, v.v.i.)

I investigate tunneling of electrons from an STM tip to a substrate through a magnetic adatom by means of the Anderson impurity model. I employ an approximation analogous to the cotunneling theory [1] and concentrate on f-electron adatoms with large spin-orbital coupling. I compare the obtained inelastic electron tunneling spectra (IETS) with predictions of the spin model that has been very successful in the case of transition-metal adatoms [2]. When the spin model is applied to f electrons, the adatom spin S is replaced with its angular momentum J [3,4].

Úterý, 13.06.2017 10:00 - 11:00

Karina Morgenstern (Chair of Physical Chemistry I; Ruhr-Universität Bochum, Germany)

While photochemistry in the gas phase demands a resonant excitation of the molecules, the presence of a metal surface in surface chemistry opens a different pathway via the creation of hot electrons in the metal and subsequent attachment of these energetic electrons to adsorbed molecules. We use two set-ups that combine a low-temperature scanning tunneling microscope operating below 10 K with a frequency doubled femto-second laser and a tunable pico-second laser, respectively, to investigate processes induced by these electrons on a single molecule basis.

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