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Author: Richter, M. × DDC: 530 ×

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Now showing 1 - 4 of 4
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    The role of the Kramers-Henneberger atom in the higher-order Kerr effect
    (Bristol : IOP, 2013) Richter, M.; Patchkovskii, S.; Morales, F.; Smirnova, O.; Ivanov, M.
    We discuss the connection between strong-field ionization, saturation of the Kerr response and the formation of the Kramers-Henneberger (KH) atom and long-living excitations in intense infrared (IR) external fields. We present a generalized model for the intensity-dependent response of atoms in strong IR laser fields, describing deviations in the nonlinear response at the frequency of the driving field from the standard model. We show that shaping the driving laser pulse allows one to reveal signatures of the excited KH states in the Kerr response of an individual atom.
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    Prediction of first-order martensitic transitions in strained epitaxial films
    (Milton Park : Taylor & Francis, 2015) Schönecke, S.; Richter, M.; Koepernik, K.; Eschrig, H.
    Coherent epitaxial growth allows us to produce strained crystalline films with structures that are unstable in the bulk. Thereby, the overlayer lattice parameters in the interface plane, (a, b), determine theminimum-energy out-of-plane lattice parameter, cmin (a, b).We showbymeans of density-functional total energy calculations that this dependence can be discontinuous and predict related firstorder phase transitions in strained tetragonal films of the elements V, Nb, Ru, La, Os, and Ir. The abrupt change of cmin can be exploited to switch properties specific to the overlayer material. This is demonstrated for the example of the superconducting critical temperature of a vanadium film which we predict to jump by 20% at a discontinuity of cmin.
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    Preparation and photoemission investigation of bulklike α-Mn films on W(110)
    (College Park : American Physical Society, 2010) Dedkov, Yu.S.; Voloshina, E.N.; Richter, M.
    We report the successful stabilization of a thick bulklike distorted α-Mn film with (110) orientation on a W(110) substrate. The observed (3×3) overstructure for the Mn film with respect to the original W(110) low-energy electron-diffraction pattern is consistent with the presented structure model. The possibility to stabilize such a pseudomorphic Mn film is supported by density-functional total-energy calculations. Angle-resolved photoemission spectra of the stabilized α-Mn(110) film show weak dispersions of the valence-band electronic states in accordance with the large unit cell.
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    Topological Electronic Structure and Intrinsic Magnetization in MnBi4Te7: A Bi2Te3 Derivative with a Periodic Mn Sublattice
    (College Park, MD : American Physical Society, 2019) Vidal, R.C.; Zeugner, A.; Facio, J.I.; Ray, R.; Haghighi, M.H.; Wolter, A.U.B.; Corredor, Bohorquez, L.T.; Caglieris, F.; Moser, S.; Figgemeier, T.; Peixoto, T.R.F.; Vasili, H.B.; Valvidares, M.; Jung, S.; Cacho, C.; Alfonsov, A.; Mehlawat, K.; Kataev, V.; Hess, C.; Richter, M.; Büchner, B.; Van Den Brink, J.; Ruck, M.; Reinert, F.; Bentmann, H.; Isaeva, A.
    Combinations of nontrivial band topology and long-range magnetic order hold promise for realizations of novel spintronic phenomena, such as the quantum anomalous Hall effect and the topological magnetoelectric effect. Following theoretical advances, material candidates are emerging. Yet, so far a compound that combines a band-inverted electronic structure with an intrinsic net magnetization remains unrealized. MnBi2Te4 has been established as the first antiferromagnetic topological insulator and constitutes the progenitor of a modular (Bi2Te3)n(MnBi2Te4) series. Here, for n=1, we confirm a nonstoichiometric composition proximate to MnBi4Te7. We establish an antiferromagnetic state below 13 K followed by a state with a net magnetization and ferromagnetic-like hysteresis below 5 K. Angle-resolved photoemission experiments and density-functional calculations reveal a topologically nontrivial surface state on the MnBi4Te7(0001) surface, analogous to the nonmagnetic parent compound Bi2Te3. Our results establish MnBi4Te7 as the first band-inverted compound with intrinsic net magnetization providing a versatile platform for the realization of magnetic topological states of matter.