Dr. Juraj Krempasky

Scientist

Paul Scherrer Institut
Forschungsstrasse 111
5232 Villigen PSI
Switzerland
Telephone
+41 56 310 51 31

Dr. Juraj Krempasky is staff member of the beamline optics group (LNO/PSD). He graduated at the Dpt. of  Solid State Physics at Technical University of Bratislava, Slovakia (1988). ​​​​​​ In 1991 he joined a fellowship at Institut de Physique Appliquée, EPFL Lausanne, where he studied optical properties of piezoelectric oxides. During 1992-2000 he worked at ELETTRA synchrotron facility where he became staff-member in the experimental controls group.  In 2000 he jointed the Swiss Light Source project at Paul Scherrer Institut as control-system specialist, where he implemented EPICS-based control concepts for SLS-1 spectroscopy beamlines. His PhD research in condensed matter physics (2004-2008) was held at Universite Cergy-Pontoise (Paris, France)  in spin- and angle-resolved photoemission on La2/3Sr1/3MnO3 correlated electron system, the experiments were carried out at SLS. In 2009 he was appointed to SLS Optics Group to become responsible for ​​​​​SLS ​photon diagnostics and advanced optics controls for spectroscopy beamlines. As an expert in the field of x-ray photon diagnostics, in collaboration with LMN laboratory he is currently responsible for x-ray grating interferometry deployment at SwissFEL for in-situ optics characterization.  

Institutional Responsabilities

Juraj Krempasky’s institutional responsabilities currently focus on photon science related to at-wavelength metrology based on grating interferometry, x-ray beam position diagnostics deployed at SLS front-ends for machine feedback; and advanced optics control for spectroscopy beam lines.

Scientific Research

Juraj Krempasky’s scientific research focus on photon science related to at-wavelength metrology, functional topological materials based on GeTe studied with spin- and angle-resolved photoemission; and magnetic dichroism from multiferroic (Ge,Mn)Te. Recently his research interest focus on light-mater interaction with photons carrying orbital angular momentum, indicating existence of a novel type of light-matter interaction with topological condensed matter.  To further support this novel research line, Dr. Krempasky was awarded a grant CZ.02.1.01/0.0/0.0/15_003/0000358.

X-ray white beam photon diagnostics advisory at:

  • MAX4 white beam monitor commissioning (2018) 
  • SOLARIS white beam monitors commissioning (2022)
  • ELETTRA-2 photon monitors upgrade (workshop 2022)   

Condensed matter physics:

Triple-point fermions in ferroelectric GeTe, J. Krempaský et al.,  Physical Review Letters, 126(20), 206403 (2021) https://doi.org/10.1103/PhysRevLett.126.206403

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Multicomponent fermions have recently been theoretically predicted, but their existence has not been unambiguously demonstrated by experiments. We resolve this crucial issue using spin-resolved ARPES in 3D spin-detection with the SARPES experimental station at SIS beamline, by which we unravel the particular spin texture around the triple point that clearly reveals its topological origin. Our results open up a new arena for studying unconventional band topologies and the formation of novel topological phases beyond topological insulators and semimetals, which we believe will lead to a variety of novel phenomena in condensed matter systems. The figure illustrates a 3D triple-point fermion cartoon, characterized by  in-plane spin-textures of the GeTe bands around the triple-point, with spin expectation values oriented mainly along Px-direction.

Earlier related research:

Operando imaging of all-electric spin texture manipulation in ferroelectric and multiferroic Rashba semiconductors, J. Krempaský et al.,  Physical Review X, 8(2), 021067 (2018), https://doi.org/10.1103/PhysRevX.8.021067

Entanglement and manipulation of the magnetic and spin-orbit order in multiferroic Rashba semiconductors, J. Krempaský et al., Nature Communications, 7, 13071 (2016). https://doi.org/10.1038/ncomms13071

Disentangling bulk and surface Rashba effects in ferroelectric α-GeTe, J. Krempaský et al.,  Physical Review B, 94(20), 205111 (2016). https://doi.org/10.1103/PhysRevB.94.205111

At-wavelength metrology:

Wavefront sensing at X-ray free-electron lasers,  Seaberg, M., Cojocaru, R., Berujon, S., Ziegler, E., Jaggi, A., Krempasky, J., … Vagovič, P. (2019), Journal of Synchrotron Radiation, 26, 1115-1126.

Vertical through-focus and focal plane intensity profile retrieved using amplitude and phase back-propagation.
Vertical through-focus and focal plane intensity profile, reconstructed from x-ray interferogram of a phase-plate corrected compound refraction lens by means of wavefront amplitude and phase back-propagation. Data were measured at SLAC XPP beamline.

For full publication list and publication metrics please refer to https://publons.com/researcher/3657577/juraj-krempasky/ and DORA:

Membership, international committee affiliations

National: Swiss Physical Society (SPS)

International committee affiliations:

National: Swiss Nanoscience Institute PhD grant co-proposer on "Local manipulation of spin domains in a multiferroic Rashba semiconductor" at SLS Pearl beamline in collaboration with Univ. Basel (https://nanoscience.ch/wp-content/uploads/sites/8/2021/07/sni_project_description_p2004.pdf, https://www.youtube.com/watch?v=Y2i1LpYMNRw)

International:  Academic career grant on “Computational and experimental design of advanced materials with new functionalities (CEDAMNF)” with reg. no. CZ.02.1.01/0.0/0.0/15_003/0000358.