VDSP Science Day 2023 - Abstracts
Creation of noble gas clusters in a graphene sandwich through low energy ion irradiation
Manuel Längle
Supervisor: Jani Kotakoski
Due to their chemical inertness, noble gases do not condense under normal conditions. When trapped between two graphene sheets, however, the atoms are forced together by the external pressure that leads to the formation of clusters [1]. We create such clusters by implanting singly charged low energy (< 30 eV) ions into suspended bi- and double layer graphene, which allows their direct imaging through (scanning) transmission electron microscopy inside the graphene sandwich [2].
So far the implantation parameters of Ar, Kr and Xe into doublelayer graphene have been experimentally determined. In our work we look at the implanted atoms, their cluster formation, stability and phase.
The encapsulated clusters show dynamical behavior such as "jumps" between different positions. Using molecular dynamics simulations we are able to understand the jumping behavior between specific positions. The trapped clusters also show interesting phase behavior. While all small clusters remain solid, larger clusters exhibit either solid- or liquid-like structures depending on their size, chemical element and possibly local microscopic environment.
Filtered annular dark field scanning transmission electron microscopy images of Xe clusters to up to seven atoms.
References
[1] Längle, M., Mizohata, K., Åhlgren, E., Trentino, A., Mustonen, K., & Kotakoski, J., Microscopy and Microanalysis, 26(S2), 1086-1089 (2020)
[2] Rasim Mirzayev, Kimmo Mustonen, Mohammad R. A. Monazam, Andreas Mittelberger,Timothy J. Pennycook, Clemens Mangler, Toma Susi, Jani Kotakoski, Jannik C. Meyer, Science Advances 3, e1700176 (2017)
Längle, Manuel1,3, Mizohata, Kenichiro2, Trentino, Alberto1,3, Mangler, Clemens1, Mustonen, Kimmo1, Åhlgren, E. Harriet1, Kotakoski, Jani 1
1 Faculty of Physics, University of Vienna, Austria
2 Department of Physics, University of Helsinki, Finland
3 Vienna Doctoral School in Physics, University of Vienna, Austria
Quantum Reference Frames in Spacetime
Viktoria Kabel
Supervisor: Caslav Brukner
When describing a physical system, it is very common to do so with respect to a reference frame - a ruler used to determine the position of a particle, for example, or a clock, which tracks the time that elapses while it is moving. Usually, reference frames are treated as purely classical objects with well-defined properties. But what happens if we take into account the quantum properties of the reference frame itself? In this highlight talk, I will give an introduction to the basic idea and formalism of quantum reference frames, which aims to address this question. Moreover, I will outline how quantum reference frames can help us better describe scenarios at the interface between quantum physics and gravity and thereby gain a deeper understanding of spacetime at the quantum level.
Polarons in Quantum Magnets
Lorenzo Celiberti
Supervisor: Cesare Franchini
Polarons and spin-orbit coupling are distinct quantum effects that play a critical role in charge transport and spin-orbitronics. Polarons originate from strong electron-phonon interaction and are ubiquitous in polarizable materials featuring electron localization, in particular 3d transition metal oxides (TMOs). On the other hand, the relativistic coupling between the spin and orbital angular momentum is notable in lattices with heavy atoms and develops in 5d TMOs, where electrons are spatially delocalized. We combined ab initio calculations and magnetic measurements to show that these two seemingly mutually exclusive interactions are entangled in the electron-doped quantum magnet Ba2Na1-xCaxOsO6, unveiling the formation of a new type of polaron.
Linked polymers in shear flow tumble differently
Reyhaneh A. Farimani
Supervisor: Christos Likos
In 1974, the Nobel Prize Winner Pierre Gilles de Gennes made a prediction that polymers subjected to shear flow would not maintain a stretched state. Instead, they would undergo cyclic tumbling motions due to the combined effects of thermal fluctuations and the shear flow field. This would cause a flipping motion in the flow-gradient plane, resulting in stretched and collapsed states. Thirty years later, this predicted tumbling motion was observed in simulation and experiment. In the last two decades, various polymer topologies were studied under shear flow and despite differences in behavior, indeed, all topologies were found to experience this type of tumbling motion. Further studies have shown that non-equilibrium polymer dynamics result from an intricate hybrid of hydrodynamic interactions (HI) and polymer topology. For example, when exposed to HI, ring polymers experience swelling in the vorticity direction.
In this presentation, we will delve into the new topic of linked ring polymers, distinguishing, in particular, between chemically linked ones and mechanically concatenated rings. Our research has revealed that the chemically bonded structure displays a unique dynamic motion in the presence of HI, tumbling in the flow-vorticity plane, also termed gradient tumbling, a motion specific to this structure and only happens in the presence of HI. On the other hand, catenated rings show yet another dynamical mode called slip tumbling. Furthermore, we will highlight how catenation affects the possibility of suspending tumbling motion through the use of a network or a chain of concatenated rings.
Schematic of a shear cell geometry. The blue arrows represent the local velocity field of a solvent sheared along the flow direction, with the velocity magnitude depending linearly on the spatial dimension along the gradient direction. The vorticity direction stands perpendicular to the other two.
Earth rotation measurement with entangled photons
Raffaele Silvestri
Supervisor: Philip Walther
I will present the first experimental measurement of the Earth's rotation induced phase shift on a two-photon maximally entangled state by means of a large-scale fiber Sagnac interferometer of milliradian phase resolution.
Identification of phononic properties of confined carbyne by Raman spectroscopy and first principle calculations
Emil Parth
Supervisor: Thomas Pichler
Carbyne is a true one dimensional allotrope of carbon, consisting of an ideallyinfinitely long chain. In theory, this material yields outstanding mechanical, optical and electronical properties. This one dimensional material is highly Raman active, and it is possible to synthesize it inside DWCNT [1][2] thus naming it confined carbyne (CC). Resonant Raman experiments reveal new features regarding an unusual specific line shape response of the G-Line fromCC@CNT which is so far not understood. We aim to reproduce these features theoretically by ab initio methods [3][4] and consequently identify the interaction types ocurring in the framework of coupled modes. Experimentally, we utilize functionalizion [5] by altering the stepwise sythesis [6] of CC@CNT which allows us to isolate specific physical interactions occurring in this interface system. The parallel comparison of theory and experiment will allow us to fully uncover the phonoic spectrum of confined carbyne alongside with its interactions to the surrounding tubes.
References
[1] W. Cui et al Angewandte Chemie (2021). DOI:10.1002/anie.202017356
[2] Lei Shi et al Nature Materials, (2016). DOI: 10.1038/nmat4617
[3] P. Giannozzi et al J. Phys.: Condens. Matter (2009). DOI: 10.1088/0953-8984/21/39/395502
[4] L. Monacelli et al J. Phys.: Condens. Matter (2021). DOI: 10.1088/1361-648X/ac066b
[5] W. Cui et al, Adv. Funct. (2022) DOI: 10.1002/adfm.202206491
[6] L. Shi et al, NanoLett. (2021); DOI: 10.1021/acs.nanolett.0c04482
E. Parth, T. Pichler, C. Freytag, C. Schuster, M. Calandra, D. Romanin, K. Yanagi, W. Cui, L. Shi
This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (MORE-TEM ERC-SYN project, grant agreement No 951215)