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Neil Wilson (University of Warwick)05/09/2023, 14:00New prospects in ARPES for quantum materialsTalk
A new parameter space to explore has been added to the beautiful world of 2D materials (2DMs); the twist angle between neighbouring layers. This is exemplified by ‘magic-angle’ twisted graphene, engineering strongly correlated behaviour through moire interactions, an effect also used to trap ordered arrays of excitons in transition metal dichalcogenide (TMDC) heterobilayers. Moire effects...
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Michael Straub05/09/2023, 14:30New prospects in ARPES for quantum materialsTalk
Recent STM experiments revealed a variety of different correlated states to coexist on the surface of bulk 1T-TaSe$_2$. The different regions have the same in-plane charge density wave ordering, yet range from insulating to strongly correlated metal. By utilizing microfocus ARPES, we have resolved the quasiparticle dispersion in the different spatial domains. In the metallic regions, we found...
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Sandy Adhitia Ekahana05/09/2023, 14:45New prospects in ARPES for quantum materialsTalk
Co3Sn2S2 has been reported to be a magnetic Weyl semimetal expanding our understanding of topological materials. This material is considered to be ferromagnetic as demonstrated experimentally and also by DFT calculations. However, recent muon measurement suggests a co-existence of antiferromagnetism and ferromagnetism around the magnetic transition temperature, which has been neglected...
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Julia Issing (University of Geneva)05/09/2023, 15:00New prospects in ARPES for quantum materialsTalk
Bulk orthorhombic T$_d$-MoTe$_2$ is a type-II Weyl semimetal with topological Fermi arc surface states and becomes superconducting at a critical temperature of $T_c = 0.1\,\text{K}$. Remarkably, superconductivity becomes far more robust in the 2D limit, contrary to generic models and the established trend in ultrathin metal films. Recent transport measurements reported an increase in $T_c$ for...
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Dr Chun Lin (University of Zurich)05/09/2023, 15:15New prospects in ARPES for quantum materialsTalk
Kagome-lattice investigations are growing vigorously owing to the simultaneous realisation of topologically non-trivial electronic structure including Dirac fermions, flat bands, and Van Hove singularities (VHS). As an effective external stimulus, uniaxial strain manifested in a form of physical pressure, is playing an increasingly important role in engineering the band structure and hence...
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Christian S. Kern05/09/2023, 15:30New prospects in ARPES for quantum materialsTalk
In order to interpret and simulate recent time- and angular-resolved photoemission spectroscopy (tr-ARPES), we extend the successful method of photoemission orbital tomography (POT) to excited states. Our theory retains the intuitive orbital picture of POT, while respecting both the entangled character of the electron-hole exciton wave function and the energy conservation in the photoemission...
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Yun Yen (Paul Scherrer Institute / EPFL)05/09/2023, 15:45New prospects in ARPES for quantum materialsTalk
In this work, we show that circular dichroism angle resolved photoemission spectroscopy (CD-ARPES) can map topology in chiral Weyl semimetals PdGa/PtGa, where multifold nodes host large Chern number[1,2]. We successfully simulate the CD intensity using our in-house code dynamics-w90[3]. The correspondence between local OAM and dipole matrix elements depends on orbital characters and...
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Victor Rosendal (Department of Energy Conversion and Storage, Technical University of Denmark)05/09/2023, 16:00New prospects in ARPES for quantum materialsTalk
Transition metal oxides could also be a platform for conceiving novel quantum properties, such as nontrivial topology induced by crystal structure modification. In this study, we investigate the effect of strain on the electronic structure and band topology of ultra-thin SrNbO3 films. By employing angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT)...
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Tom van Waas (Université catholique de Louvain)05/09/2023, 16:15New prospects in ARPES for quantum materialsTalk
In ARPES, access to the electronic spectral function $A(E,\mathbf{k})$ is obscured by the photoemission matrix elements $M_{\mathbf{k}_f,\mathbf{k}}$ [1]. We provide a heuristic approach based on the sum rule [2] to obtain the momentum dependence of these elements. We show how matrix element correction (MEC) enables extraction of the Eliashberg spectral function from both light band branches...
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Gunther Springholz (Institut für Halbleiter-und Festkörperphysik, Johannes Kepler Universität, Linz, Austria)05/09/2023, 17:00New prospects in ARPES for quantum materialsTalk
Angle resolved photoemission spectroscopy (APRES) has emerged as a powerful tool to assess the electronic band structure of quantum materials. Here, it is applied to study quantum confined states in IV-VI semiconductor and topological insulator heterostructures produced by molecular beam epitaxy. This allows to study a large variety of low dimensional structures revealing the electronic...
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Mr Frédéric Chassot (Department of Physics and Fribourg Center for Nanomaterials, Université de Fribourg, Fribourg, Switzerland)05/09/2023, 17:30New prospects in ARPES for quantum materialsTalk
SnTe is a ferroelectric semiconductor with similar properties as GeTe, which has already been extensively studied, notably for applications in spintronics. However, the lower critical temperature of SnTe (around 100K) makes it an ideal candidate to investigate the ferroelectric transition. Here we present a study of its bandstructure with photoemission spectroscopy. We follow the evolution of...
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Vladimir N. Strocov (Swiss Light Source, Paul Scherrer Institute)05/09/2023, 17:45New prospects in ARPES for quantum materialsTalk
Three-dimensional (3D) electronic bandstructure is fundamental for a vast diversity of physical phenomena in solid-state materials, including topological phases, interlayer interactions in van-der-Waals materials, etc. Interpretation of ARPES data in terms of 3D bandstructure is commonly based on the free-electron approximation for the photoemission final states. Our soft-X-ray ARPES data on...
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Michael Schüler (Paul Scherrer Institute / University of Fribourg)05/09/2023, 18:00New prospects in ARPES for quantum materialsTalk
Angle-resolved photoemission spectroscopy (ARPES) provides an unprecedented “zoom” into the electronic degrees of freedom. Besides mapping the band structure, fingerprints of wave-function aspects such as the orbital texture, associated orbital angular momentum (OAM) and Berry curvature are contained in ARPES. Extracting such wave-function information is a challenge due to the complexity of...
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Dominik Brandstetter (University of Graz)05/09/2023, 18:30New prospects in ARPES for quantum materialsTalk
Real-time time-dependent density functional theory provides an ab-initio framework to directly simulate (sub-)femtosecond pump-probe ARPES experiments. Incident light field(s) of any shape and magnitude can be incorporated, electron correlations are considered at a mean-field level and no assumptions regarding the final state of the escaping electron are required. In this contribution, we...
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Anna Hartl (Paul Scherrer Institut)05/09/2023, 18:45New prospects in ARPES for quantum materialsTalk
In ARPES, coupling of polarized light to the valence-band states contains valuable information about their orbital and spin texture. This information, however, is distorted by non-trivial behavior of the photoemission matrix elements. We explored the circular dichroism in InAs(110) over a broad photon-energy range from VUV to soft X-rays, focusing on the Fermi-surface maps. Supported by ARPES...
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