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42 results on '"Kummer, K."'

1. Detection of a two-phonon mode in a cuprate superconductor via polarimetric resonant inelastic x-ray scattering

Author

Scott, K., primary, Kisiel, E., additional, Yakhou, F., additional, Agrestini, S., additional, Garcia-Fernandez, M., additional, Kummer, K., additional, Choi, J., additional, Zhong, R. D., additional, Schneeloch, J. A., additional, Gu, G. D., additional, Zhou, Ke-Jin, additional, Brookes, N. B., additional, Kemper, A. F., additional, Minola, M., additional, Boschini, F., additional, Frano, A., additional, Gozar, A., additional, and da Silva Neto, E. H., additional

Published
2024
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2. Metamagnetism and crystal-field splitting in pseudohexagonal CeRh3Si2

Author

Amorese, A, Khalyavin, D, Kummer, K, Brookes, NB, Ritter, C, Zaharko, O, Larsen, CB, Pavlosiuk, O, Pikul, AP, Kaczorowski, D, Gutmann, M, Boothroyd, AT, Severing, A, and Adroja, DT

Abstract

CeRh 3 Si 2 has been reported to exhibit metamagnetic transitions below 5 K, a giant crystal field splitting, and anisotropic magnetic properties from single crystal magnetization and heat capacity measurements. Here we report results of neutron and x-ray scattering studies of the magnetic structure and crystal-field excitations to further understand the magnetism of this compound. Inelastic neutron scattering and resonant inelastic x-ray scattering reveal a J z = 1 / 2 ground state for Ce when considering the crystallographic a direction as quantization axis, thus explaining the anisotropy of the static susceptibility. Furthermore, we find a total splitting of 78 meV for the J = 5 / 2 multiplet. The neutron diffraction study in zero field reveals that, on cooling from the paramagnetic state, the system first orders at T N 1 = 4.7 K in a longitudinal spin density wave with ordered Ce moments along the b axis (i.e., the [0 1 0] crystal direction) and an incommensurate propagation vector k = ( 0 , 0.43 , 0 ). Below the lower-temperature transition T N 2 = 4.48 K , the propagation vector locks to the commensurate value k = ( 0 , 0.5 , 0 ) , with a so-called lock-in transition. Our neutron diffraction study in applied magnetic field H ∥ b axis shows a change in the commensurate propagation vector and development of a ferromagnetic component at H = 3 kOe , followed by a series of transitions before the fully field-induced ferromagnetic phase is reached at H = 7 kOe . This explains the nature of the steps previously reported in field-dependent magnetization measurements. A very similar behavior is also observed for the H ∥ [0 1 1] crystal direction.

Published
2022
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3. Electronic structure and coexistence of superconductivity with magnetism in RbEuFe4As4

Author

Kim, T. K., primary, Pervakov, K. S., additional, Evtushinsky, D. V., additional, Jung, S. W., additional, Poelchen, G., additional, Kummer, K., additional, Vlasenko, V. A., additional, Sadakov, A. V., additional, Usoltsev, A. S., additional, Pudalov, V. M., additional, Roditchev, D., additional, Stolyarov, V. S., additional, Vyalikh, D. V., additional, Borisov, V., additional, Valentí, R., additional, Ernst, A., additional, Eremeev, S. V., additional, and Chulkov, E. V., additional

Published
2021
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5. Photoelectron diffraction for probing valency and magnetism of 4f -based materials: A view on valence-fluctuating EuIr2Si2

Author

Usachov, D. Yu., primary, Tarasov, A. V., additional, Schulz, S., additional, Bokai, K. A., additional, Tupitsyn, I. I., additional, Poelchen, G., additional, Seiro, S., additional, Caroca-Canales, N., additional, Kliemt, K., additional, Mende, M., additional, Kummer, K., additional, Krellner, C., additional, Muntwiler, M., additional, Li, Hang, additional, Laubschat, C., additional, Geibel, C., additional, Chulkov, E. V., additional, Fujimori, S. I., additional, and Vyalikh, D. V., additional

Published
2020
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10. Polarization-resolved Cu L3 -edge resonant inelastic x-ray scattering of orbital and spin excitations in NdBa2Cu3O7−δ

Author

Fumagalli, R., primary, Braicovich, L., additional, Minola, M., additional, Peng, Y. Y., additional, Kummer, K., additional, Betto, D., additional, Rossi, M., additional, Lefrançois, E., additional, Morawe, C., additional, Salluzzo, M., additional, Suzuki, H., additional, Yakhou, F., additional, Le Tacon, M., additional, Keimer, B., additional, Brookes, N. B., additional, Sala, M. Moretti, additional, and Ghiringhelli, G., additional

Published
2019
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12. Coupling between dynamic magnetic and charge-order correlations in the cuprate superconductor Nd2−xCexCuO4

Author

da Silva Neto, E. H., primary, Minola, M., additional, Yu, B., additional, Tabis, W., additional, Bluschke, M., additional, Unruh, D., additional, Suzuki, H., additional, Li, Y., additional, Yu, G., additional, Betto, D., additional, Kummer, K., additional, Yakhou, F., additional, Brookes, N. B., additional, Le Tacon, M., additional, Greven, M., additional, Keimer, B., additional, and Damascelli, A., additional

Published
2018
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13. Dispersion, damping, and intensity of spin excitations in the monolayer (Bi,Pb)2(Sr,La)2CuO6+δ cuprate superconductor family

Author

Peng, Y. Y., primary, Huang, E. W., additional, Fumagalli, R., additional, Minola, M., additional, Wang, Y., additional, Sun, X., additional, Ding, Y., additional, Kummer, K., additional, Zhou, X. J., additional, Brookes, N. B., additional, Moritz, B., additional, Braicovich, L., additional, Devereaux, T. P., additional, and Ghiringhelli, G., additional

Published
2018
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14. Strong spin-orbit coupling in the noncentrosymmetric Kondo lattice

Author

Generalov, A., primary, Falke, J., additional, Nechaev, I. A., additional, Otrokov, M. M., additional, Güttler, M., additional, Chikina, A., additional, Kliemt, K., additional, Seiro, S., additional, Kummer, K., additional, Danzenbächer, S., additional, Usachov, D., additional, Kim, T. K., additional, Dudin, P., additional, Chulkov, E. V., additional, Laubschat, C., additional, Geibel, C., additional, Krellner, C., additional, and Vyalikh, D. V., additional

Published
2018
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16. Microscopic effects of Dy doping in the topological insulator Bi2Te3

Author

Duffy, L. B., primary, Steinke, N.-J., additional, Krieger, J. A., additional, Figueroa, A. I., additional, Kummer, K., additional, Lancaster, T., additional, Giblin, S. R., additional, Pratt, F. L., additional, Blundell, S. J., additional, Prokscha, T., additional, Suter, A., additional, Langridge, S., additional, Strocov, V. N., additional, Salman, Z., additional, van der Laan, G., additional, and Hesjedal, T., additional

Published
2018
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17. Evolution of ground-state wave function in CeCoIn5 upon Cd or Sn doping

Author

Chen, K., primary, Strigari, F., additional, Sundermann, M., additional, Hu, Z., additional, Fisk, Z., additional, Bauer, E. D., additional, Rosa, P. F. S., additional, Sarrao, J. L., additional, Thompson, J. D., additional, Herrero-Martin, J., additional, Pellegrin, E., additional, Betto, D., additional, Kummer, K., additional, Tanaka, A., additional, Wirth, S., additional, and Severing, A., additional

Published
2018
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21. Valence instability in the bulk and at the surface of the antiferromagnet SmRh2Si2

Author

Chikina, A., primary, Generalov, A., additional, Kummer, K., additional, Güttler, M., additional, Antonov, V. N., additional, Kucherenko, Yu., additional, Kliemt, K., additional, Krellner, C., additional, Danzenbächer, S., additional, Kim, T., additional, Dudin, P., additional, Geibel, C., additional, Laubschat, C., additional, and Vyalikh, D. V., additional

Published
2017
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23. Direct observation of charge order in underdoped and optimally doped Bi2(Sr,La)2CuO6+δ by resonant inelastic x-ray scattering

Author

Peng, Y. Y., primary, Salluzzo, M., additional, Sun, X., additional, Ponti, A., additional, Betto, D., additional, Ferretti, A. M., additional, Fumagalli, F., additional, Kummer, K., additional, Le Tacon, M., additional, Zhou, X. J., additional, Brookes, N. B., additional, Braicovich, L., additional, and Ghiringhelli, G., additional

Published
2016
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27. Laser-induced charge-disproportionated metallic state inLaCoO3

Author

Izquierdo, M., primary, Karolak, M., additional, Trabant, C., additional, Holldack, K., additional, Föhlisch, A., additional, Kummer, K., additional, Prabhakaran, D., additional, Boothroyd, A. T., additional, Spiwek, M., additional, Belozerov, A., additional, Poteryaev, A., additional, Lichtenstein, A., additional, and Molodtsov, S. L., additional

Published
2014
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28. Tracing the localization of4felectrons: Angle-resolved photoemission onYbCo2Si2, the stable trivalent counterpart of the heavy-fermionYbRh2Si2

Author

Güttler, M., primary, Kummer, K., additional, Patil, S., additional, Höppner, M., additional, Hannaske, A., additional, Danzenbächer, S., additional, Shi, M., additional, Radovic, M., additional, Rienks, E., additional, Laubschat, C., additional, Geibel, C., additional, and Vyalikh, D. V., additional

Published
2014
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29. Direct observation of bulk charge modulations in optimally dopedBi1.5Pb0.6Sr1.54CaCu2O8+δ

Author

Hashimoto, M., primary, Ghiringhelli, G., additional, Lee, W.-S., additional, Dellea, G., additional, Amorese, A., additional, Mazzoli, C., additional, Kummer, K., additional, Brookes, N. B., additional, Moritz, B., additional, Yoshida, Y., additional, Eisaki, H., additional, Hussain, Z., additional, Devereaux, T. P., additional, Shen, Z.-X., additional, and Braicovich, L., additional

Published
2014
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30. Magnetic excitations in stripe-ordered La1.875Ba0.125CuO4studied using resonant inelastic x-ray scattering

Author

Dean, M. P. M., primary, Dellea, G., additional, Minola, M., additional, Wilkins, S. B., additional, Konik, R. M., additional, Gu, G. D., additional, Le Tacon, M., additional, Brookes, N. B., additional, Yakhou-Harris, F., additional, Kummer, K., additional, Hill, J. P., additional, Braicovich, L., additional, and Ghiringhelli, G., additional

Published
2013
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34. Intermediate valence in Yb compounds probed by 4fphotoemission and resonant inelastic x-ray scattering

Author

Kummer, K., primary, Kucherenko, Yu., additional, Danzenbächer, S., additional, Krellner, C., additional, Geibel, C., additional, Holder, M. G., additional, Bekenov, L. V., additional, Muro, T., additional, Kato, Y., additional, Kinoshita, T., additional, Huotari, S., additional, Simonelli, L., additional, Molodtsov, S. L., additional, Laubschat, C., additional, and Vyalikh, D. V., additional

Published
2011
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35. Evolution of magnetism in Yb(Rh1−xCox)2Si2

Author

Klingner, C., primary, Krellner, C., additional, Brando, M., additional, Geibel, C., additional, Steglich, F., additional, Vyalikh, D. V., additional, Kummer, K., additional, Danzenbächer, S., additional, Molodtsov, S. L., additional, Laubschat, C., additional, Kinoshita, T., additional, Kato, Y., additional, and Muro, T., additional

Published
2011
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37. Valence instability in the bulk and at the surface of the antiferromagnet SmRh2Si2.

Author

Chikina, A., Generalov, A., Kummer, K., Güttler, M., Antonov, V. N., Kucherenko, Yu., Kliemt, K., Krellner, C., Danzenbächer, S., Kim, T., Dudin, P., Geibel, C., Laubschat, C., and Vyalikh, D. V.

Subjects
*ANTIFERROMAGNETIC materials, *ELECTRONIC structure, *PHOTOELECTRON spectroscopy
Abstract

Using resonant angle-resolved photoemission spectroscopy and electron band-structure calculations, we explore the electronic structure and properties of Sm atoms at the surface and in the bulk of the antiferromagnet SmRh2Si2. We show that the Sm atoms reveal weak mixed-valent behavior both in the bulk and at the surface. Although trivalent 4f emission strongly dominates, a small divalent 4f signal near the Fermi energy can be clearly resolved for surface and bulk Sm atoms. This behavior is quite different to most other Sm-based materials which typically experience a surface valence transition to a divalent state of Sm atoms at the surface. This phenomenon is explained in analogy to the isostructural Ce compound, where strong 4f hybridization stabilizes mixed-valent ground state both in the bulk and at the surface, and which were described in the light of the single-impurity Anderson model. Implications for other RERh2Si2 (RE = rare-earth elements) compounds are discussed. [ABSTRACT FROM AUTHOR]

Published
2017
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38. GdRh2Si2: An exemplary tetragonal system for antiferromagnetic order with weak in-plane anisotropy.

Author

Kliemt, K., Hofmann-Kliemt, M., Kummer, K., Yakhou-Harris, F., Krellner, C., and Geibel, C.

Subjects
*ANISOTROPY, *ANTIFERROMAGNETIC materials, *TETRAGONAL crystal system
Abstract

The anisotropy of magnetic properties commonly is introduced in textbooks using the case of an antiferromagnetic system with Ising type anisotropy. This model presents huge anisotropic magnetization and a pronounced metamagnetic transition and is well-known and well-documented both in experiments and theory. In contrast, the case of an antiferromagnetic X-Y system with weak in-plane anisotropy is only poorly documented. We studied the anisotropic magnetization of the compound GdRh2Si2 and found that it is a perfect model system for such a weak-anisotropy setting because the Gd3+ ions in GdRh2Si2 have a pure spin moment of S=7/2, which orders in a simple AFM structure with Q=(001). We observed experimentally in M(B) a continuous spin-flop transition and domain effects for a field applied along the [100] and the [110] direction, respectively. We applied a mean-field model for the free energy to describe our data and combine it with an Ising chain model to account for domain effects. Our calculations reproduce the experimental data very well. In addition, we performed magnetic x-ray scattering and x-ray magnetic circular dichroism measurements, which confirm the AFM propagation vector to be Q=(001) and indicate the absence of polarization on the rhodium atoms. [ABSTRACT FROM AUTHOR]

Published
2017
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39. Evolution of ground-state wave function in CeCoIn5 upon Cd or Sn doping.

Author

Chen, K., Strigari, F., Sundermann, M., Hu, Z., Fisk, Z., Bauer, E. D., Rosa, P. F. S., Sarrao, J. L., Thompson, J. D., Herrero-Martin, J., Pellegrin, E., Betto, D., Kummer, K., Tanaka, A., Wirth, S., and Severing, A.

Subjects
*SEMICONDUCTOR doping, *X-ray absorption spectra, *X-ray spectroscopy, *LINEAR polarization, *GROUND state (Quantum mechanics), *ANTIFERROMAGNETISM, *CONDUCTION electrons
Abstract

We present linear polarization-dependent soft-x-ray absorption spectroscopy data at the Ce M4, 5 edges of Cd- and Sn-doped CeCoIn5. The 4f ground-state wave functions have been determined for their superconducting, antiferromagnetic, and paramagnetic ground states. The absence of changes in the wave functions in CeCo In1-x Cdx) 5 suggests that the 4f-conduction-electron (cf) hybridization is not affected by global Cd doping, thus supporting the interpretation of magnetic droplets nucleating long-range magnetic order. This is contrasted by changes in the wave function due to Sn substitution. Increasing Sn in CeCo ( In1-y Sny)5 compresses the 4f orbitals into the tetragonal plane of these materials, suggesting enhanced cf hybridization with the in-plane In(1) atoms and a homogeneous altering of the electronic structure. As these experiments show, the 4f wave functions are a very sensitive probe of small changes in the hybridization of 4f and conduction electrons, even conveying information about direction dependencies. [ABSTRACT FROM AUTHOR]

Published
2018
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40. Magnetic proximity coupling to Cr-doped Sb2Te3 thin films.

Author

Duffy, L. B., Figueroa, A. I., Gładczuk, Ł., Steinke, N.-J., Kummer, K., van der Laan, G., and Hesjedal, T.

Subjects
*THIN films, *ANTIMONY compounds, *TELLURIUM compounds
Abstract

Using soft x-ray absorption spectroscopy we determined the chemical and magnetic properties of the magnetic topological insulator (MTI) Cr:Sb2Te3. X-ray magnetic circular dichroism (XMCD) at the Cr L2,3, Te M4,5, and Sb M4,5 edges shows that the Te 5p moment is aligned antiparallel to both the Cr 3d and Sb 5p moments, which is characteristic for carrier-mediated ferromagnetic coupling. Comparison of the Cr L2,3 spectra with multiplet calculations indicates a hybridized Cr state, consistent with the carrier-mediated coupling scenario. We studied the enhancement of the Curie temperature, TC, of the MTI thin film through the magnetic proximity effect. Arrott plots, measured using the Cr L3 XMCD, show a TC ≈ 87 K for the as-cleaved film. After deposition of a thin layer of ferromagnetic Co onto the surface, the TC increases to ∼93 K, while the Co and Cr moments are parallel. This increase in TC is unexpectedly small compared to similar systems reported earlier. The XMCD spectra demonstrate that the Co/MTI interface remains intact, i.e., no reaction between Co and the MTI takes place. Our results are a useful starting point for refining the physical models of Cr-doped Sb2Te3, which is required for making use of them in device applications. [ABSTRACT FROM AUTHOR]

Published
2017
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41. Direct observation of charge order in underdoped and optimally doped Bi2(Sr,La)2CuO6+δ by resonant inelastic x-ray scattering.

Author

Peng, Y. Y., Salluzzo, M., Sun, X., Ponti, A., Betto, D., Ferretti, A. M., Fumagalli, F., Kummer, K., Le Tacon, M., Zhou, X. J., Brookes, N. B., Braicovich, L., and Ghiringhelli, G.

Subjects
*COPPER oxide, *INELASTIC scattering, *SUPERCONDUCTORS
Abstract

Charge order in underdoped and optimally doped high-Tc superconductors Bi2-x(Sr,La)2CuO6+δ (Bi2201) is investigated by Cu L3 edge resonant inelastic x-ray scattering. We have directly observed charge density modulation in the optimally doped Bi2201 at momentum transfer Q||≃0.23 reciprocal lattice units, with smaller intensity and correlation length with respect to the underdoped sample. This demonstrates the short-range charge order in Bi2201 persists up to optimal doping, as in other hole-doped cuprates. We explored the nodal (diagonal) direction and found no charge order peak, confirming that charge density modulates only along the Cu-O bond directions. We measured the out-of-plane dependence of charge order, finding a flat response and no maxima at half integer L values. This suggests there is no out-of-plane phase correlation in single layer Bi2201, at variance from YBa2Cu3O6+x and La2-x(Ba,Sr)xCuO4. Combining our results with data from the literature we assess that charge order in Bi2201 exists in a large doping range across the phase diagram, i.e., 0.07≲p≲0.16, demonstrating thereby that it is intimately entangled with the antiferromagnetic background, the pseudogap, and superconductivity. [ABSTRACT FROM AUTHOR]

Published
2016
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42. 4f excitations in Ce Kondo lattices studied by resonant inelastic x-ray scattering.

Author

Amorese, A., Dellea, G., Fanciulli, M., Seiro, S., Geibel, C., Krellner, C., Makarova, I. P., Braicovich, L., Ghiringhelli, G., Vyalikh, D. V., Brookes, N. B., and Kummer, K.

Subjects
*CERIUM, *INELASTIC scattering, *KONDO effect
Abstract

The potential of resonant inelastic soft x-ray scattering to measure 4f crystal electric-field excitation spectra in Ce Kondo lattices has been examined. Spectra have been obtained for several Ce systems and show a well-defined structure determined by crystal-field, spin-orbit, and charge-transfer excitations only. The spectral shapes of the excitation spectra can be well understood in the framework of atomic multiplet calculations. For CeCu2Si2 we found notable disagreement between the inelastic x-ray-scattering spectra and theoretical calculations when using the crystal-field scheme proposed from inelastic neutron scattering. Modified sets of crystal-field parameters yield better agreement. Our results also show that, with the very recent improvements of soft x-ray spectrometers in resolution to below 30 meV at the Ce M4,5 edges, resonant inelastic x-ray scattering could be an ideal tool to determine the crystal-field scheme in Ce Kondo lattices and other rare-earth compounds. [ABSTRACT FROM AUTHOR]

Published
2016
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