Prof. Jascha Repp

University of Regensburg, Germany
Jascha Repp studied physics at the Free University of Berlin, where he earned his doctorate in 2002. Following that, he held a post-doctoral position in Gerhard Meyer's group at the IBM Research Laboratory in Rüschlikon, Switzerland. In 2007 he became physics professor at the University of Regensburg. Repp's research focuses on the examination of individual atoms, molecules, and nanostructures on surfaces using scanning probe microscopy. His contributions to the field include the development of several innovative techniques, offering profound insights into the understanding of individual molecules. In recognition of his collaborative efforts, Jascha Repp, alongside Leo Gross and Gerhard Meyer, was awarded the Feynman Prize in Nanotechnology in 2012. In 2021 he received an ERC Synergy grant together with Leo Gross and Diego Peña.

Talk title: Accessing non-equilibrium at the intrinsic scales of molecules

While scanning probe microscopy (SPM) has revolutionized our understanding of the atomistic world it is usually too slow to capture non-equilibrium excitation processes. Two complementary approaches that allow accessing non-equilibrium phenomena with SPM will be presented.

Accessing ultra-fast phenomena is enabled by combining lightwave electronics with scanning tunneling microscopy (STM), allowing for combined femtosecond and sub-angstrom resolution in observing matter (1). Lightwave STM also provides access in the control of matter by utilizing localized electric fields to exert atom-scale femtosecond forces (2). Further, we show how lightwave STM can be extended to its ultrafast spectroscopy variant (3). The corresponding ultrafast and atomically resolved tunnelling spectra reveal transient energy shifts of a single selenium vacancy in a WSe2 monolayer on gold.

Another approach gives us access to intermediate timescales that are relevant for spin precession and relaxations. We exploit the high sensitivity of atomic force microscopy (AFM) to perform STM and spectroscopy on molecules in absence of any conductance of the underlying substrate. Thereby, we gain access to out-of-equilibrium charge states (4) that are out of reach for conventional STM. Extending this technique by electronic pump-probe spectroscopy, we measured the triplet lifetime of individual molecules and its quenching by nearby oxygen molecules (5). Combined with radio-frequency magnetic-field driving we introduce AFM-based electron spin resonance and spin manipulation showing long spin coherence in single molecules (6).

References:
(1)    T. Cocker et al., Nature 539, 263 (2016).
(2)    D. Peller et al., Nature 585, 58 (2020).
(3)    C. Roelcke et al., in press (2023).
(4)    L. L. Patera et al., Nature 566, 245 (2019).
(5)    J. Peng et al., Science 373, 452 (2021).
(6)    L. Sellies et al., Nature 624, 64 (2023).