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1. Optical signatures of interlayer electron coherence in a bilayer semiconductor

Author

Liu, Xiaoling, Leisgang, Nadine, Dolgirev, Pavel E., Zibrov, Alexander A., Sung, Jiho, Wang, Jue, Taniguchi, Takashi, Watanabe, Kenji, Walther, Valentin, Park, Hongkun, Demler, Eugene, Kim, Philip, and Lukin, Mikhail D.

Subjects
Condensed Matter - Strongly Correlated Electrons
Abstract

Emergent strongly-correlated electronic phenomena in atomically-thin transition metal dichalcogenides are an exciting frontier in condensed matter physics, with examples ranging from bilayer superconductivity~\cite{zhao2023evidence} and electronic Wigner crystals~\cite{smolenski2021signatures,zhou2021bilayer} to the ongoing quest for exciton condensation~\cite{wang2019evidence,ma2021strongly,shi2022bilayer}. Here, we experimentally investigate the properties of indirect excitons in naturally-grown MoS$_2$-homobilayer, integrated in a dual-gate device structure allowing independent control of the electron density and out-of-plane electric field. Under conditions when electron tunneling between the layers is negligible~\cite{pisoni2019absence}, upon electron doping the sample, we observe that the two excitons with opposing dipoles hybridize, displaying unusual behavior distinct from both conventional level crossing and anti-crossing. We show that these observations can be explained by static random coupling between the excitons, which increases with electron density and decreases with temperature. We argue that this phenomenon is indicative of a spatially fluctuating order parameter in the form of interlayer electron coherence, a theoretically predicted many-body state~\cite{zheng1997exchange} that has yet to be unambiguously established experimentally outside of the quantum Hall regime~\cite{sarma2008perspectives,spielman2000resonantly,kellogg2004vanishing,kellogg2002observation,spielman2001observation,fertig1989energy,shi2022bilayer}. Implications of our findings for future experiments and quantum optics applications are discussed.

Published
2024

3. Exchange energy of the ferromagnetic electronic ground-state in a monolayer semiconductor

Author

Leisgang, Nadine, Miserev, Dmitry, Mattiat, Hinrich, Schneider, Lukas, Sponfeldner, Lukas, Watanabe, Kenji, Taniguchi, Takashi, Poggio, Martino, and Warburton, Richard J.

Subjects
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Mobile electrons in the semiconductor monolayer-MoS$_2$ form a ferromagnetic state at low temperature. The Fermi sea consists of two circles, one at the $K$-point, the other at the $\tilde{K}$-point, both with the same spin. Here, we present an optical experiment on gated MoS$_2$ at low electron-density in which excitons are injected with known spin and valley quantum numbers. The resulting trions are identified using a model which accounts for the injection process, the formation of antisymmetrized trion states, electron-hole scattering from one valley to the other, and recombination. The results are consistent with a complete spin polarization. From the splittings between different trion states, we measure the exchange energy, $\Sigma$, the energy required to flip a single spin within the ferromagnetic state, as well as the intervalley Coulomb exchange energy, $J$. We determine $\Sigma=11.2\,$meV and $J=5\,$meV at $n=1.5 \times 10^{12}\,$cm$^{-2}$, and find that $J$ depends strongly on the electron density, $n$., Comment: 13 pages, 11 figures

Published
2023

4. Adult-onset Still’s disease masquerading as acute coronary syndrome: a case report and review of the literature

Author

Indigo Milne, Rhea Kanwar, Whitney Martin, Daniel Egert, Allison Leisgang, Shirley A. Albano-Aluquin, Maria P. Henao, Christine Kreider, and Paddy Ssentongo

Subjects
Adult-onset Still’s disease, Fever of unknown origin, Hemophagocytic lymphohistiocytosis, Bone marrow biopsy, Medicine
Abstract

Abstract Introduction Adult-onset Still’s disease is a rare systemic autoinflammatory disease. We present a case of a young man with a constellation of symptoms and myopericarditis as a complication of this disease. Case A 36-year-old Hispanic man with no significant past medical history developed a quotidian fever pattern following an upper respiratory tract infection. He initially presented with chest pain concerning for myocardial infarction and underwent cardiac catheterization, which revealed non-obstructive coronary artery disease. He was found to have myopericarditis, significant neutrophilic leukocytosis, and hyperferritinemia. He improved on high-dose corticosteroids but developed steroid-induced psychosis, and 4 months from symptom onset, he finally received tocilizumab, which eventually induced remission without adverse reactions. Discussion Adult-onset Still’s disease should be considered in a patient with fevers of undetermined origin. Due to its multisystemic involvement, adult-onset Still’s disease is often a diagnosis arrived at after an extensive cardiac, hematologic, malignant, and infectious workup. Imaging, laboratory testing, and bone marrow biopsy were necessary to rule out alternative etiologies of this patient’s presentation. Steroids are the mainstay of treatment because they are easily affordable, although the high risk of adverse effects makes them less desirable. Interleukin-1 inhibitors (anakinra or canakinumab) and interleukin-6 inhibitor tocilizumab are the steroid-sparing biologic agents of choice but are cost-prohibitive. Conclusion Adult-onset Still’s disease should be considered in the differential diagnoses of fever of undetermined origin. Early identification and initiation of treatment are critical to faster recovery and prevention of progression to severe complications. Steroids remain the standard first-line therapy and should be followed by disease-modifying steroid sparing drugs. The social determinants of health may preclude their timely initiation and should alert providers of proactive ways to avoid further delays.

Published
2024
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10. Capacitively-coupled and inductively-coupled excitons in bilayer MoS$_2$

Author

Sponfeldner, Lukas, Leisgang, Nadine, Shree, Shivangi, Paradisanos, Ioannis, Watanabe, Kenji, Taniguchi, Takashi, Robert, Cedric, Lagarde, Delphine, Balocchi, Andrea, Marie, Xavier, Gerber, Iann C., Urbaszek, Bernhard, and Warburton, Richard J.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The interaction of intralayer and interlayer excitons is studied in a two-dimensional semiconductor, homobilayer MoS$_2$. It is shown that the measured optical susceptibility reveals both the magnitude and the sign of the coupling constants. The interlayer exciton interacts capacitively with the intralayer B-exciton (positive coupling constant) consistent with hole tunnelling from one monolayer to the other. Conversely, the interlayer exciton interacts inductively with the intralayer A-exciton (negative coupling constant). First-principles many-body calculations show that this coupling arises via an intravalley exchange-interaction of A- and B-excitons., Comment: Main text: 6 pages, 4 figures; Supplementary Information: 17 pages, 15 figures

Published
2021
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11. Clinical and biological relevance of glial fibrillary acidic protein in Alzheimer’s disease

Author

Zhengshi Yang, Karthik Sreenivasan, Erin N. Toledano Strom, Amanda M. Leisgang Osse, Lorenzo Gabriel Pasia, Celica Glenn Cosme, Maya Rae N. Mugosa, Emma Léa Chevalier, Aaron Ritter, Justin B. Miller, Dietmar Cordes, Jeffrey L. Cummings, and Jefferson W. Kinney

Subjects
Glial fibrillary acidic protein, Alzheimer’s disease, Ptau-181, ATN framework, 18F-AV45, Neurosciences. Biological psychiatry. Neuropsychiatry, RC321-571, Neurology. Diseases of the nervous system, RC346-429
Abstract

Abstract Introduction There is a tremendous need for identifying reliable blood-based biomarkers for Alzheimer’s disease (AD) that are tied to the biological ATN (amyloid, tau and neurodegeneration) framework as well as clinical assessment and progression. Methods One hundred forty-four elderly participants underwent 18F-AV45 positron emission tomography (PET) scan, structural magnetic resonance imaging (MRI) scan, and blood sample collection. The composite standardized uptake value ratio (SUVR) was derived from 18F-AV45 PET to assess brain amyloid burden, and the hippocampal volume was determined from structural MRI scans. Plasma glial fibrillary acidic protein (GFAP), phosphorylated tau-181 (ptau-181), and neurofilament light (NfL) measured by single molecular array (SIMOA) technology were assessed with respect to ATN framework, genetic risk factor, age, clinical assessment, and future functional decline among the participants. Results Among the three plasma markers, GFAP best discriminated participants stratified by clinical diagnosis and brain amyloid status. Age was strongly associated with NfL, followed by GFAP and ptau-181 at much weaker extent. Brain amyloid was strongly associated with plasma GFAP and ptau-181 and to a lesser extent with plasma NfL. Moderate association was observed between plasma markers. Hippocampal volume was weakly associated with all three markers. Elevated GFAP and ptau-181 were associated with worse cognition, and plasma GFAP was the most predictive of future functional decline. Combining GFAP and ptau-181 together was the best model to predict brain amyloid status across all participants (AUC = 0.86) or within cognitively impaired participants (AUC = 0.93); adding NfL as an additional predictor only had a marginal improvement. Conclusion Our findings indicate that GFAP is of potential clinical utility in screening amyloid pathology and predicting future cognitive decline. GFAP, NfL, and ptau-181 were moderately associated with each other, with discrepant relevance to age, sex, and AD genetic risk, suggesting their relevant but differential roles for AD assessment. The combination of GFAP with ptau-181 provides an accurate model to predict brain amyloid status, with the superior performance of GFAP over ptau-181 when the prediction is limited to cognitively impaired participants.

Published
2023
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14. Giant Stark splitting of an exciton in bilayer MoS$_2$

Author

Leisgang, Nadine, Shree, Shivangi, Paradisanos, Ioannis, Sponfeldner, Lukas, Robert, Cedric, Lagarde, Delphine, Balocchi, Andrea, Watanabe, Kenji, Taniguchi, Takashi, Marie, Xavier, Warburton, Richard J., Gerber, Iann C., and Urbaszek, Bernhard

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

Transition metal dichalcogenides (TMDs) constitute a versatile platform for atomically thin optoelectronics devices and spin-valley memory applications. In monolayers optical absorption is strong, but the transition energy is not tunable as the neutral exciton has essentially no out-of-plane electric dipole. In contrast, interlayer exciton transitions in heterobilayers are widely tunable in applied electric fields, but their coupling to light is considerably reduced. Here, we show tuning over 120 meV of interlayer excitons with high oscillator strength in bilayer MoS2. These shifts are due to the quantum confined Stark effect, here the electron is localised to one of the layers yet the hole is delocalised across the bilayer. We optically probe the interaction between intra- and interlayer excitons as they are energetically tuned into resonance. This allows studying their mixing supported by beyond standard density functional theory calculations including excitonic effects. In MoS2 trilayers our experiments uncover two types of interlayer excitons with and without in-built electric dipoles, respectively. Highly tunable excitonic transitions with large oscillator strength and in-built dipoles, that lead to considerable exciton-exciton interactions, hold great promise for non-linear optics with polaritons., Comment: final author version

Published
2020
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15. Controlling interlayer excitons in MoS2 layers grown by chemical vapor deposition

Author

Paradisanos, Ioannis, Shree, Shivangi, George, Antony, Leisgang, Nadine, Robert, Cedric, Watanabe, Kenji, Taniguchi, Takashi, Warburton, Richard J., Turchanin, Andrey, Marie, Xavier, Gerber, Iann C., and Urbaszek, Bernhard

Subjects
Condensed Matter - Materials Science
Abstract

Combining MoS$_2$ monolayers to form multilayers allows to access new functionalities. In this work, we examine the correlation between the stacking order and the interlayer coupling of valence states in MoS$_2$ homobilayer samples grown by chemical vapor deposition (CVD) and artificially stacked bilayers from CVD monolayers. We show that hole delocalization over the bilayer is allowed in 2H stacking and results in strong interlayer exciton absorption and also in a larger A-B exciton separation as compared to 3R bilayers, where both holes and electrons are confined to the individual layers. Comparing 2H and 3R reflectivity spectra allows to extract an interlayer coupling energy of about $t_\perp=49$ meV. Obtaining very similar results for as-grown and artificially stacked bilayers is promising for assembling large area van der Waals structures with CVD material, using interlayer exciton absorption and A-B exciton separation as indicators for interlayer coupling. Beyond DFT calculations including excitonic effects confirm signatures of efficient interlayer coupling for 2H stacking in agreement with our experiments., Comment: 10 pages including supplement, 3 + 4 figures

Published
2020
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16. First-order magnetic phase-transition of mobile electrons in monolayer MoS$_2$

Author

Roch, Jonas Gaël, Miserev, Dmitry, Froehlicher, Guillaume, Leisgang, Nadine, Sponfeldner, Lukas, Watanabe, Kenji, Taniguchi, Takashi, Klinovaja, Jelena, Loss, Daniel, and Warburton, Richard John

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Evidence is presented for a first-order magnetic phase transition in a gated two-dimensional semiconductor, monolayer-MoS$_2$. The phase boundary separates a spin-polarised (ferromagnetic) phase at low electron density and a paramagnetic phase at high electron density. Abrupt changes in the optical response signal an abrupt change in the magnetism. The magnetic order is thereby controlled via the voltage applied to the gate electrode of the device. Accompanying the change in magnetism is a large change in the electron effective mass.

Published
2019
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18. Optical second harmonic generation in encapsulated single-layer InSe

Author

Leisgang, Nadine, Roch, Jonas G., Froehlicher, Guillaume, Hamer, Matthew, Terry, Daniel, Gorbachev, Roman, and Warburton, Richard J.

Subjects
Physics - Optics, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We report the observation of optical second harmonic generation (SHG) in single-layer indium selenide (InSe). We measure a second harmonic signal of $>10^3$ $\textrm{cts/s}$ under nonresonant excitation using a home-built confocal microscope and a standard pulsed pico-second laser. We demonstrate that polarization-resolved SHG serves as a fast, non-invasive tool to determine the crystal axes in single-layer InSe and to relate the sharp edges of the flake to the armchair and zigzag edges of the crystal structure. Our experiment determines these angles to an accuracy better than $\pm$ $0.2^{\circ}$. Treating the two-dimensional material as a nonlinear polarizable sheet, we determine a second-order nonlinear sheet polarizability $| \chi_{\textrm{sheet}}^{(2)}|=(17.9 \pm 11.0)\times 10^{-20}$ $\textrm{m}^2 \textrm{V}^{-1}$ for single-layer InSe, corresponding to an effective nonlinear susceptibility value of $| \chi_\textrm{eff}^{(2)}| \approx (223 \pm 138) \times 10^{-12}$ $\textrm{m} \textrm{V}^{-1}$ accounting for the sheet thickness ($\textrm{d} \approx 0.8$ $\textrm{nm}$). We demonstrate that the SHG technique can also be applied to encapsulated samples to probe their crystal orientations. The method is therefore suitable for creating high quality van der Waals heterostructures with control over the crystal directions.

Published
2018

19. Spin-Polarized Electrons in Monolayer MoS$_2$

Author

Roch, Jonas G., Froehlicher, Guillaume, Leisgang, Nadine, Makk, Peter, Watanabe, Kenji, Taniguchi, Takashi, and Warburton, Richard J.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Physics - Optics
Abstract

The optical susceptibility is a local, minimally-invasive and spin-selective probe of the ground state of a two-dimensional electron gas. We apply this probe to a gated monolayer of MoS$_2$. We demonstrate that the electrons are spin polarized. Of the four available bands, only two are occupied. These two bands have the same spin but different valley quantum numbers. We argue that strong Coulomb interactions are a key aspect of this spontaneous symmetry breaking. The Bohr radius is so small that even electrons located far apart in phase space interact, facilitating exchange couplings to align the spins.

Published
2018
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20. Quantum confined Stark effect in a MoS$_2$ monolayer van der Waals heterostructure

Author

Roch, Jonas G., Leisgang, Nadine, Froehlicher, Guillaume, Makk, Peter, Watanabe, Kenji, Taniguchi, Takashi, Schönenberger, Christian, and Warburton, Richard J.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Optics
Abstract

The optics of dangling-bond-free van der Waals heterostructures containing transition metal dichalcogenides are dominated by excitons. A crucial property of a confined exciton is the quantum confined Stark effect (QCSE). Here, such a heterostructure is used to probe the QCSE by applying a uniform vertical electric field across a molybdenum disulfide (MoS$_2$) monolayer. The photoluminescence emission energies of the neutral and charged excitons shift quadratically with the applied electric field provided the electron density remains constant, demonstrating that the exciton can be polarized. Stark shifts corresponding to about half the homogeneous linewidth were achieved. Neutral and charged exciton polarizabilities of $(7.8~\pm~1.0)\times 10^{-10}~\tr{D~m~V}^{-1}$ and $(6.4~\pm~0.9)\times 10^{-10}~\tr{D~m~V}^{-1}$ at relatively low electron density ($8 \times 10^{11}~\tr{cm}^{-2}$) have been extracted, respectively. These values are one order of magnitude lower than the previously reported values, but in line with theoretical calculations. The methodology presented here is versatile and can be applied to other semiconducting layered materials as well.

Published
2017
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25. Controlling interlayer excitons in MoS2 layers grown by chemical vapor deposition

Author

Ioannis Paradisanos, Shivangi Shree, Antony George, Nadine Leisgang, Cedric Robert, Kenji Watanabe, Takashi Taniguchi, Richard J. Warburton, Andrey Turchanin, Xavier Marie, Iann C. Gerber, and Bernhard Urbaszek

Subjects
Science
Abstract

The authors investigate the interplay between the stacking order and the interlayer coupling in MoS2 homobilayers as well as artificially stacked bilayers grown by chemical vapour deposition, and identify the interlayer exciton absorption and A-B exciton separation as indicators for interlayer coupling.

Published
2020
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26. Visual analytics of soccer player performance using objective ratings.

Author

Evers, Marina, Derstroff, Adrian, Leistikow, Simon, Schneider, Tom, Mallepree, Larissa, Stampke, Jan, Leisgang, Moritz, Sprafke, Sebastian, Schuhl, Melina, Krefft, Niklas, Droese, Felix, and Linsen, Lars

Subjects
SOCCER players, VISUAL analytics, SOCCER, TASK analysis, DATA visualization
Abstract

The performance of soccer players is commonly rated by soccer experts for each match as well as over a tournament or during a season/year. However, these ratings are mostly subjective. We instead propose a visual analytics approach for a more objective, data-driven analysis of soccer players' performances. We introduce data-driven ratings for various aspects, which can be combined by interactively assigning weights to compute an overall score as well as individual scores for passes, duels, and shots. Our tool supports comparative visualizations at a global level that can be adapted to different analysis tasks as well as in-detail analyses of individual events of the game. We apply our approach to data gathered during the 2020 UEFA European Football Championship and perform in-detail analyses of individual players in selected matches. [ABSTRACT FROM AUTHOR]

Published
2024
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32. Reduction in GABAB on glia induce Alzheimer’s disease related changes

Author

Leisgang Osse, Amanda M., primary, Pandey, Ravi S., additional, Wirt, Ryan A., additional, Ortiz, Andrew A., additional, Salazar, Arnold, additional, Kimmich, Michael, additional, Strom, Erin N., additional, Oblak, Adrian, additional, Lamb, Bruce, additional, Hyman, James M., additional, Carter, Gregory W., additional, and Kinney, Jefferson, additional

Published
2023
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35. Optical second harmonic generation in encapsulated single-layer InSe

Author

Nadine Leisgang, Jonas G. Roch, Guillaume Froehlicher, Matthew Hamer, Daniel Terry, Roman Gorbachev, and Richard J. Warburton

Subjects
Physics, QC1-999
Abstract

We report the observation of optical second harmonic generation (SHG) in single-layer indium selenide (InSe). We measure a second harmonic signal of > 103 cts/s under nonresonant excitation using a home-built confocal microscope and a standard pulsed pico-second laser. We demonstrate that polarization-resolved SHG serves as a fast, non-invasive tool to determine the crystal axes in single-layer InSe and to relate the sharp edges of the flake to the armchair and zigzag edges of the crystal structure. Our experiment determines these angles to an accuracy better than ± 0.2°. Treating the two-dimensional material as a nonlinear polarizable sheet, we determine a second-order sheet polarizability |χsheet(2)|=(17.9 ± 11.0)×10−20 m2 V−1 for single-layer InSe, corresponding to an effective nonlinear susceptibility value of |χeff(2)|≈(223 ± 138)×10−12 m V−1 accounting for the sheet thickness (d ≈ 0.8 nm). We demonstrate that the SHG technique can also be applied to encapsulated samples to probe their crystal orientations. The method is therefore suitable for creating high quality van der Waals heterostructures with control over the crystal directions.

Published
2018
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36. Capacitively and Inductively Coupled Excitons in Bilayer MoS 2

Author

Lukas Sponfeldner, Nadine Leisgang, Shivangi Shree, Ioannis Paradisanos, Kenji Watanabe, Takashi Taniguchi, Cedric Robert, Delphine Lagarde, Andrea Balocchi, Xavier Marie, Iann C. Gerber, Bernhard Urbaszek, Richard J. Warburton, Department of Physics and Astronomy [Basel], University of Basel (Unibas), Laboratoire de physique et chimie des nano-objets (LPCNO), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Fédération de recherche « Matière et interactions » (FeRMI), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and National Institute for Materials Science (NIMS)

Subjects
General Physics and Astronomy, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat]
Abstract

The coupling of intralayer A and B excitons and interlayer excitons (IE) is studied in a two-dimensional semiconductor, homobilayer MoS_{2}. It is shown that the measured optical susceptibility reveals both the magnitude and the phase of the coupling constants. The IE and B excitons couple via a 0-phase (capacitive) coupling; the IE and A excitons couple via a π-phase (inductive) coupling. The IE-B and IE-A coupling mechanisms are interpreted as hole tunneling and electron-hole exchange, respectively. The couplings imply that even in a monolayer, the A and B excitons have mixed spin states. Using the IE as a sensor, the A-B intravalley exchange coupling is determined. Finally, we realize a bright and highly tunable lowest-energy momentum-direct exciton at high electric fields.

Published
2022
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37. Capacitively and Inductively Coupled Excitons in Bilayer MoS2

Author

Sponfeldner, Lukas, primary, Leisgang, Nadine, additional, Shree, Shivangi, additional, Paradisanos, Ioannis, additional, Watanabe, Kenji, additional, Taniguchi, Takashi, additional, Robert, Cedric, additional, Lagarde, Delphine, additional, Balocchi, Andrea, additional, Marie, Xavier, additional, Gerber, Iann C., additional, Urbaszek, Bernhard, additional, and Warburton, Richard J., additional

Published
2022
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38. Denileukin diftitox (ONTAK) induces a tolerogenic phenotype in dendritic cells and stimulates survival of resting Treg

Author

Baur, Andreas S., Lutz, Manfred B., Schierer, Stephan, Beltrame, Luca, Theiner, Gabi, Zinser, Elisabeth, Ostalecki, Christian, Heidkamp, Gordon, Haendle, Ina, Erdmann, Michael, Wiesinger, Manuel, Leisgang, Waltraud, Gross, Stefanie, Pommer, Ansgar J., Kämpgen, Eckhart, Dudziak, Diana, Steinkasserer, Alexander, Cavalieri, Duccio, Schuler-Thurner, Beatrice, and Schuler, Gerold

Published
2013
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40. Detrital zircon provenance of the Archean Moodies Group, Barberton Greenstone Belt, South Africa and Eswatini

Author

Heubeck, Christoph, primary, Drabon, Nadja, additional, Byerly, Gary, additional, Leisgang, Isabelle, additional, Linnemann, Ulf, additional, Lowe, Don, additional, Mertz-Kraus, Regina, additional, Gonzalez-Pinzon, Alejandra, additional, Thomsen, Tonny B., additional, Zeh, Armin, additional, Rojas-Agramonte, Yamirka, additional, and Kröner, Alfred, additional

Published
2022
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41. Electrical control of excitons in a gated two-dimensional semiconductor

Author

Leisgang, Nadine Martine, Warburton, Richard J., Zardo, Ilaria, and Wurstbauer, Ursula

Subjects
Condensed Matter::Mesoscopic Systems and Quantum Hall Effect
Abstract

The emergence of two-dimensional (2D) materials, such as graphene and transition metal dichalcogenides (TMDs), and the ability to build artificial van der Waals heterostructures (vdWHs) by stacking different combinations of materials, has opened a new route for engineering quantum systems. 2D TMDs support bound electron-hole pairs, or excitons, that have particularly large binding energies, such that excitons dominate their optical properties, even at room temperature. The ability to electrically tune their properties via external electric gates is essential for various interesting opto-electronic applications. A crucial feature of semiconductor nanostructures is the quantum confined Stark effect (QCSE), the change in optical energy on applying an electric field perpendicular to the layers. Using a gated vdWH, we demonstrated that in monolayer MoS$_2$ optical absorption is strong, but the transition energy is not tunable as the neutral exciton has essentially no permanent out-of-plane electric dipole and is only slightly polarizable. The electrical control of excitons via the QCSE requires larger polarizabilities or a non-zero dipole moment as observed in heterobilayers where the bound electrons and holes reside in different layers. However, the coupling to light in these systems is considerably reduced. To combine best of both worlds, a polarizable yet strong optical dipole, we integrated homobilayer MoS$_2$ in a dual-gate device structure. In its natural bilayer form, we discovered interlayer excitons which exhibit both a high oscillator strength and highly tunable energies in an applied electric field. Owing to their very large dipole moments, we were able to bring these interlayer excitons energetically close to resonance with the excitons confined to the single layers, and study exciton-exciton interactions in these systems. Equipping MoS$_2$ with gates allows electrons to be injected, creating a 2D electron gas. By probing the electronic ground state at various electron densities, we presented experimental evidence for a spontaneous spin-polarization in monolayer MoS$_2$. Significantly, the extremely small Bohr radius of an electron in this material suggests that Coulomb effects play an important role at experimental relevant electron densities. The ability to control the properties of thin semiconductors by electrical means makes these systems a versatile platform for rich exciton physics and unique opto-electronic applications.

Published
2021
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42. Controlling interlayer excitons in MoS2 layers grown by chemical vapor deposition

Author

Takashi Taniguchi, Xavier Marie, Andrey Turchanin, Ioannis Paradisanos, Antony George, Richard J. Warburton, Bernhard Urbaszek, Nadine Leisgang, Kenji Watanabe, Iann C. Gerber, Shivangi Shree, Cedric Robert, Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), Optoélectronique Quantique (LPCNO), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), and ANR-17-CE30-0028,2D-vdW-Spin,Dynamique de Spin et de Valle´e dans les Mate´riaux bidimensionnels de van der Waals(2017)

Subjects
Materials science, Science, Exciton, Stacking, FOS: Physical sciences, General Physics and Astronomy, 02 engineering and technology, Chemical vapor deposition, 01 natural sciences, General Biochemistry, Genetics and Molecular Biology, Condensed Matter::Materials Science, Delocalized electron, symbols.namesake, Condensed Matter::Superconductivity, 0103 physical sciences, Monolayer, 010306 general physics, lcsh:Science, ComputingMilieux_MISCELLANEOUS, [PHYS.COND.CM-MSQHE]Physics [physics]/Condensed Matter [cond-mat]/Mesoscopic Systems and Quantum Hall Effect [cond-mat.mes-hall], Condensed Matter - Materials Science, Multidisciplinary, Valence (chemistry), Bilayer, Materials Science (cond-mat.mtrl-sci), General Chemistry, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, 021001 nanoscience & nanotechnology, Chemical physics, symbols, lcsh:Q, van der Waals force, 0210 nano-technology
Abstract

Combining MoS$_2$ monolayers to form multilayers allows to access new functionalities. In this work, we examine the correlation between the stacking order and the interlayer coupling of valence states in MoS$_2$ homobilayer samples grown by chemical vapor deposition (CVD) and artificially stacked bilayers from CVD monolayers. We show that hole delocalization over the bilayer is allowed in 2H stacking and results in strong interlayer exciton absorption and also in a larger A-B exciton separation as compared to 3R bilayers, where both holes and electrons are confined to the individual layers. Comparing 2H and 3R reflectivity spectra allows to extract an interlayer coupling energy of about $t_\perp=49$ meV. Obtaining very similar results for as-grown and artificially stacked bilayers is promising for assembling large area van der Waals structures with CVD material, using interlayer exciton absorption and A-B exciton separation as indicators for interlayer coupling. Beyond DFT calculations including excitonic effects confirm signatures of efficient interlayer coupling for 2H stacking in agreement with our experiments., Comment: 10 pages including supplement, 3 + 4 figures

Published
2020
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43. Giant Stark splitting of an exciton in bilayer MoS

Author

Nadine, Leisgang, Shivangi, Shree, Ioannis, Paradisanos, Lukas, Sponfeldner, Cedric, Robert, Delphine, Lagarde, Andrea, Balocchi, Kenji, Watanabe, Takashi, Taniguchi, Xavier, Marie, Richard J, Warburton, Iann C, Gerber, and Bernhard, Urbaszek

Abstract

Transition metal dichalcogenides (TMDs) constitute a versatile platform for atomically thin optoelectronics devices and spin-valley memory applications. In monolayer TMDs the optical absorption is strong, but the transition energy cannot be tuned as the neutral exciton has essentially no out-of-plane static electric dipole

Published
2020

44. Alterations of GABA B receptors in the APP/PS1 mouse model of Alzheimer's disease

Author

Amanda M. Leisgang, Arnold Salazar, Andrew A. Ortiz, Andrew S. Murtishaw, and Jefferson W. Kinney

Subjects
0301 basic medicine, Aging, Amyloid, Amyloid beta, Glutamate decarboxylase, Spatial Learning, Glutamic Acid, Mice, Transgenic, GABAB receptor, 03 medical and health sciences, 0302 clinical medicine, Alzheimer Disease, Memory, medicine, GABA transporter, Animals, Receptor, gamma-Aminobutyric Acid, Microglia, biology, General Neuroscience, Disease Models, Animal, 030104 developmental biology, medicine.anatomical_structure, nervous system, Receptors, GABA-B, biology.protein, GABAergic, Neurology (clinical), Geriatrics and Gerontology, Neuroscience, Neuroglia, 030217 neurology & neurosurgery, Developmental Biology, Signal Transduction
Abstract

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by the progressive decline of memory and cognitive function. The disease is characterized by the presence of amyloid plaques, tau tangles, altered inflammatory signaling, and alterations in numerous neurotransmitter signaling systems, including γ-aminobutyric acid (GABA). Given the extensive role of GABA in regulating neuronal activity, a careful investigation of GABA-related changes is needed. Further, given persistent inflammation has been demonstrated to drive AD pathology, the presence of GABA B receptor expressed on glia that serve a role regulation of the immune response adds to potential implications of altered GABA in AD. There has not previously been a systematic evaluation of GABA-related changes in an amyloid model of AD that specifically focuses on examining changes in GABA B receptors. In the present study, we examined alterations in several GABA-specific targets in the APP/PS1 mouse model at different ages. In the 4-month-old cohort, no significant deficits in spatial learning and memory or alterations in any of the GABAergic targets were observed compared with wild-type controls. However, we identified significant alterations in several GABA-related targets in the 6-month-old cohort that exhibited spatial learning deficits that include changes in glutamic acid decarboxylase 65, GABA transporter type 3, and GABA B receptors protein and mRNA levels. This was the same cohort at which learning and memory deficits and significant amyloid pathology was observed. Overall, our study provides evidence of altered GABAergic signaling in an amyloid model of AD at a time point consistent with AD-related deficits.

Published
2020

45. Giant Stark splitting of an exciton in bilayer MoS$_2$

Author

Takashi Taniguchi, Andrea Balocchi, Delphine Lagarde, Kenji Watanabe, Shivangi Shree, Nadine Leisgang, Cedric Robert, Xavier Marie, Ioannis Paradisanos, Bernhard Urbaszek, Richard J. Warburton, Iann C. Gerber, Lukas Sponfeldner, Optoélectronique Quantique (LPCNO), Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and ANR-17-CE30-0028,2D-vdW-Spin,Dynamique de Spin et de Valle´e dans les Mate´riaux bidimensionnels de van der Waals(2017)

Subjects
Materials science, Oscillator strength, Exciton, Biomedical Engineering, FOS: Physical sciences, Bioengineering, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Condensed Matter::Materials Science, Electric field, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Polariton, General Materials Science, Electrical and Electronic Engineering, [PHYS.COND.CM-MSQHE]Physics [physics]/Condensed Matter [cond-mat]/Mesoscopic Systems and Quantum Hall Effect [cond-mat.mes-hall], Condensed Matter::Quantum Gases, Condensed Matter - Materials Science, Condensed matter physics, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter::Other, Bilayer, Resonance, Materials Science (cond-mat.mtrl-sci), 021001 nanoscience & nanotechnology, Condensed Matter Physics, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Atomic and Molecular Physics, and Optics, 0104 chemical sciences, Dipole, Electric dipole moment, 0210 nano-technology
Abstract

Transition metal dichalcogenides (TMDs) constitute a versatile platform for atomically thin optoelectronics devices and spin-valley memory applications. In monolayers optical absorption is strong, but the transition energy is not tunable as the neutral exciton has essentially no out-of-plane electric dipole. In contrast, interlayer exciton transitions in heterobilayers are widely tunable in applied electric fields, but their coupling to light is considerably reduced. Here, we show tuning over 120 meV of interlayer excitons with high oscillator strength in bilayer MoS2. These shifts are due to the quantum confined Stark effect, here the electron is localised to one of the layers yet the hole is delocalised across the bilayer. We optically probe the interaction between intra- and interlayer excitons as they are energetically tuned into resonance. This allows studying their mixing supported by beyond standard density functional theory calculations including excitonic effects. In MoS2 trilayers our experiments uncover two types of interlayer excitons with and without in-built electric dipoles, respectively. Highly tunable excitonic transitions with large oscillator strength and in-built dipoles, that lead to considerable exciton-exciton interactions, hold great promise for non-linear optics with polaritons., Comment: final author version

Published
2020
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46. Ergonomie in der Klein- und Serienfertigung

Author

Johannes Brombach and Michael Leisgang

Abstract

Die angesprochenen Fertigungsbereiche sind das Leitwerk fur Stahlfertigung fur Grosfahrzeuge. Unter Nutzung modernster Produktionstechnologien sowie einer hochflexiblen Montage auf Basis des unternehmensspezifischen Produktionssystems entstehen Fahrzeuge mit hochstem Nutzen fur die Kunden und die Umwelt. Die Fertigung zeichnet sich durch eine grose Vielfalt an unterschiedlichen Varianten aus, die in kleinen Serien gefertigt werden. Das Produkt ist hoch komplex und durch seine raumliche Ausdehnung stellt es hohe Anforderung an die Logistik im Werk.

Published
2020
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47. Geostandards and Geoanalytical Research Bibliographic Review 2017

Author

Anna Reichstein, Viktoria Kaiser, Klaus Peter Jochum, Uwe Nohl, Florentine Zwillich, Ulrike Weis, Beate Schwager, Isabelle Leisgang, and Brigitte Stoll

Subjects
Certified reference materials, Materials science, Geochemistry and Petrology, 010401 analytical chemistry, Library science, Geology, 010502 geochemistry & geophysics, 01 natural sciences, 0104 chemical sciences, 0105 earth and related environmental sciences
Published
2018
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48. Inflammation as a central mechanism in Alzheimer's disease

Author

Bruce T. Lamb, Arnold Salazar, Amanda M. Leisgang, Jefferson W. Kinney, Andrew S. Murtishaw, and Shane M. Bemiller

Subjects
0301 basic medicine, Amyloid, Special Issue from the Centers of Biomedical Research Excellence (COBRE) and Center for Neurodegeneration and Translational Neuroscience (CNTN), Microglia receptors, Inflammation, Disease, Pathogenesis, 03 medical and health sciences, 0302 clinical medicine, Immune system, medicine, Cognitive decline, Microglia, business.industry, Mechanism (biology), Alzheimer's disease, 3. Good health, Psychiatry and Mental health, 030104 developmental biology, medicine.anatomical_structure, Cytokines, Neurology (clinical), medicine.symptom, business, Neuroscience, 030217 neurology & neurosurgery
Abstract

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is characterized by cognitive decline and the presence of two core pathologies, amyloid β plaques and neurofibrillary tangles. Over the last decade, the presence of a sustained immune response in the brain has emerged as a third core pathology in AD. The sustained activation of the brain's resident macrophages (microglia) and other immune cells has been demonstrated to exacerbate both amyloid and tau pathology and may serve as a link in the pathogenesis of the disorder. In the following review, we provide an overview of inflammation in AD and a detailed coverage of a number of microglia-related signaling mechanisms that have been implicated in AD. Additional information on microglia signaling and a number of cytokines in AD are also reviewed. We also review the potential connection of risk factors for AD and how they may be related to inflammatory mechanisms.

Published
2018
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49. Geostandards and Geoanalytical Research Bibliographic Review 2016

Author

Florentine Zwillich, Isabelle Leisgang, Brigitte Stoll, Uwe Nohl, Klaus Peter Jochum, Ulrike Weis, Patricia Karlowski, and Beate Schwager

Subjects
Geochemistry and Petrology, 010401 analytical chemistry, Environmental science, Geology, 010502 geochemistry & geophysics, 01 natural sciences, 0104 chemical sciences, 0105 earth and related environmental sciences
Published
2017
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