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Langmann J, Eickerling G, Scherer W. X-ray diffraction – a suitable probe for superconductivity? Acta Cryst Sect A 2022. [DOI: 10.1107/s2053273322095602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2023]
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Ebad-Allah J, Rojewski S, Vöst M, Eickerling G, Scherer W, Uykur E, Sankar R, Varrassi L, Franchini C, Ahn KH, Kuneš J, Kuntscher CA. Pressure-Induced Excitations in the Out-of-Plane Optical Response of the Nodal-Line Semimetal ZrSiS. Phys Rev Lett 2021; 127:076402. [PMID: 34459638 DOI: 10.1103/physrevlett.127.076402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 06/17/2021] [Indexed: 06/13/2023]
Abstract
The anisotropic optical response of the layered, nodal-line semimetal ZrSiS at ambient and high pressure is investigated by frequency-dependent reflectivity measurements for the polarization along and perpendicular to the layers. The highly anisotropic optical conductivity is in very good agreement with results from density-functional theory calculations and confirms the anisotropic character of ZrSiS. Whereas the in-plane optical conductivity shows only modest pressure-induced changes, we found strong effects on the out-of-plane optical conductivity spectrum of ZrSiS, with the appearance of two prominent excitations. These pronounced pressure-induced effects can neither be attributed to a structural phase transition according to our single-crystal x-ray diffraction measurements, nor can they be explained by electronic correlation and electron-hole pairing effects, as revealed by theoretical calculations. Our findings are discussed in the context of the recently proposed excitonic insulator phase in ZrSiS.
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Affiliation(s)
- J Ebad-Allah
- Experimentalphysik II, University of Augsburg, 86159 Augsburg, Germany
- Department of Physics, Tanta University, 31527 Tanta, Egypt
| | - S Rojewski
- Experimentalphysik II, University of Augsburg, 86159 Augsburg, Germany
| | - M Vöst
- Chair of Chemical Physics and Materials Science, Institute of Physics, University of Augsburg, 86159 Augsburg, Germany
| | - G Eickerling
- Chair of Chemical Physics and Materials Science, Institute of Physics, University of Augsburg, 86159 Augsburg, Germany
| | - W Scherer
- Chair of Chemical Physics and Materials Science, Institute of Physics, University of Augsburg, 86159 Augsburg, Germany
| | - E Uykur
- 1. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
| | - Raman Sankar
- Institute of Physics, Academia Sinica, Taipei 11529, Taiwan
| | - L Varrassi
- Department of Physics and Astronomy, Alma Mater Studiorum-Università di Bologna, Bologna 40127, Italy
| | - C Franchini
- Department of Physics and Astronomy, Alma Mater Studiorum-Università di Bologna, Bologna 40127, Italy
- University of Vienna, Faculty of Physics and Center for Computational Materials Science, 1090 Vienna, Austria
| | - K-H Ahn
- Institute of Solid State Physics, TU Wien, 1020 Vienna, Austria
- Institute of Physics, The Czech Academy of Sciences, 16200 Praha, Czechia
| | - J Kuneš
- Institute of Solid State Physics, TU Wien, 1020 Vienna, Austria
- Institute of Physics, The Czech Academy of Sciences, 18221 Praha, Czechia
| | - C A Kuntscher
- Experimentalphysik II, University of Augsburg, 86159 Augsburg, Germany
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Geirhos K, Langmann J, Prodan L, Tsirlin AA, Missiul A, Eickerling G, Jesche A, Tsurkan V, Lunkenheimer P, Scherer W, Kézsmárki I. Cooperative Cluster Jahn-Teller Effect as a Possible Route to Antiferroelectricity. Phys Rev Lett 2021; 126:187601. [PMID: 34018769 DOI: 10.1103/physrevlett.126.187601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 03/02/2021] [Accepted: 04/08/2021] [Indexed: 06/12/2023]
Abstract
We report the observation of an antipolar phase in cubic GaNb_{4}S_{8} driven by an unconventional microscopic mechanism, the cooperative Jahn-Teller effect of Nb_{4}S_{4} molecular clusters. The assignment of the antipolar nature is based on sudden changes in the crystal structure and a strong drop of the dielectric constant at T_{JT}=31 K, also indicating the first-order nature of the transition. In addition, we found that local symmetry lowering precedes long-range orbital ordering, implying the presence of a dynamic Jahn-Teller effect in the cubic phase above T_{JT}. Based on the variety of structural polymorphs reported in lacunar spinels, also including ferroelectric phases, we argue that GaNb_{4}S_{8} may be transformable to a ferroelectric state, which would further classify the observed antipolar phase as antiferroelectric.
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Affiliation(s)
- K Geirhos
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
| | - J Langmann
- CPM, Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - L Prodan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
- Institute of Applied Physics, MD 2028, Chisinau, Republic of Moldova
| | - A A Tsirlin
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
| | - A Missiul
- CELLS-ALBA Synchrotron, Cerdanyola del Valles, E-08290 Barcelona, Spain
| | - G Eickerling
- CPM, Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - A Jesche
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
| | - V Tsurkan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
- Institute of Applied Physics, MD 2028, Chisinau, Republic of Moldova
| | - P Lunkenheimer
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
| | - W Scherer
- CPM, Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - I Kézsmárki
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
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Scheidt EW, Fischer A, Wybranski O, Eickerling G, Scherer W, Baenitz M, Mayr F, Heying B, Pöttgen R. Complex magnetic order from multiple Ce-sites in Ce 3Pd 4Sn 6. J Phys Condens Matter 2017; 29:315801. [PMID: 28598335 DOI: 10.1088/1361-648x/aa787a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Polycrystalline [Formula: see text] [Formula: see text] [Formula: see text] samples were synthesized by arc-melting and subsequent annealing at 970 K. Specific heat, electrical resistivity and magnetic susceptibility measurements are performed over a wide range in temperature and provide hints for the presence of a complex magnetic ordering below 3 K arising from three crystallographically independent Ce sites. This behaviour is driven by a complex interplay between ferro-, ferri-, and antiferromagnetic correlations among the Ce atoms.
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Affiliation(s)
- E-W Scheidt
- CPM, Institut für Physik, Universität Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany
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Gold C, Gross P, Peyker L, Eickerling G, Simeoni GG, Stockert O, Kampert E, Wolff-Fabris F, Michor H, Scheidt EW. Interplay between crystal field splitting and Kondo effect in CeNi9Ge(4-x)Si(x). J Phys Condens Matter 2012; 24:355601. [PMID: 22885655 DOI: 10.1088/0953-8984/24/35/355601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The pseudo-ternary solid solution CeNi(9)Ge(4-x)Si(x) (0 ≤ x ≤ 4) has been investigated by means of x-ray diffraction, magnetic susceptibility, specific heat, electrical resistivity, thermopower and inelastic neutron scattering studies. The isoelectronic substitution of germanium by silicon atoms causes a dramatic change of the relative strength of competing Kondo, RKKY and crystal field (CF) energy scales. The strongest effect is the continuous elevation of the Kondo temperature T(K) from approximately 3.5 K for CeNi(9)Ge(4) to about 70 K for CeNi(9)Si(4). This increase of the Kondo temperature is attended by a change of the CF level scheme of the Ce ions. The interplay of the different energy scales results in an incipient reduction of the ground state degeneracy from an effectively fourfold degenerate non-magnetic Kondo ground state with unusual non-Fermi-liquid features of CeNi(9)Ge(4) to a lower one, followed by an increase towards a sixfold, fully degenerate ground state multiplet in CeNi(9)Si(4) (T(K) ∼ Δ(CF)).
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Affiliation(s)
- C Gold
- CPM, Institut für Physik, Universität Augsburg, Augsburg, Germany
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Fischer A, Tiana D, Scherer W, Batke K, Eickerling G, Svendsen H, Bindzus N, Iversen BB. Experimental and theoretical charge density studies at subatomic resolution. J Phys Chem A 2011; 115:13061-71. [PMID: 21863852 DOI: 10.1021/jp2050405] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Analysis of accurate experimental and theoretical structure factors of diamond and silicon reveals that the contraction of the core shell due to covalent bond formation causes significant perturbations of the total charge density that cannot be ignored in precise charge density studies. We outline that the nature and origin of core contraction/expansion and core polarization phenomena can be analyzed by experimental studies employing an extended Hansen-Coppens multipolar model. Omission or insufficient treatment of these subatomic charge density phenomena might yield erroneous thermal displacement parameters and high residual densities in multipolar refinements. Our detailed studies therefore suggest that the refinement of contraction/expansion and population parameters of all atomic shells is essential to the precise reconstruction of electron density distributions by a multipolar model. Furthermore, our results imply that also the polarization of the inner shells needs to be adopted, especially in cases where second row or even heavier elements are involved in covalent bonding. These theoretical studies are supported by direct multipolar refinements of X-ray powder diffraction data of diamond obtained from a third-generation synchrotron-radiation source (SPring-8, BL02B2).
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Affiliation(s)
- A Fischer
- Institute of Physics, University of Augsburg, Augsburg, Germany
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Eickerling G, Batke K, Scherer W. Relativistic effects on the topology of the electron density. Acta Crystallogr A 2011. [DOI: 10.1107/s010876731109790x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Scherer W, Eyert V, Eickerling G, Rohrmoser B, Kaecke R, Hauf C, Poettgen R, Vogt C, Hoffmann RD, Rodewald U. Electron localization phenomena in complex carbides of rare earth and transition metals. Acta Crystallogr A 2008. [DOI: 10.1107/s0108767308095895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Killer U, Scheidt EW, Eickerling G, Michor H, Sereni J, Pruschke T, Kehrein S. Unusual single-ion non-fermi-liquid behavior in Ce(1-x)LaxNi9Ge4. Phys Rev Lett 2004; 93:216404. [PMID: 15601039 DOI: 10.1103/physrevlett.93.216404] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2004] [Indexed: 05/24/2023]
Abstract
We report on specific heat, magnetic susceptibility, and resistivity measurements on the compound Ce(1-x)LaxNi9Ge4 for various concentrations ranging from the stoichiometric system with x = 0 to the dilute limit x = 0.95. Our data reveal single-ion scaling with the Ce concentration and the largest ever recorded value of the electronic specific heat Deltac/T approximately 5.5 J K-2 mol(-1) at T = 0.08 K for the stoichiometric compound x = 0 without any trace of magnetic order. While in the doped samples Deltac/T increases logarithmically below 3 K down to 50 mK, their magnetic susceptibility behaves Fermi-liquid-like below 1 K. These properties make the compound Ce(1-x)LaxNi9Ge4 a unique system on the borderline between Fermi-liquid and non-Fermi-liquid physics.
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Affiliation(s)
- U Killer
- CPM, Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany
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Eickerling G, Tafipolsky M, Scherer W, McGrady GS, Chatterton NP. Characterisation of the Mn(hapto(2)-SiH) interaction by analysis of experimental and theoretical charge densities. Acta Crystallogr A 2002. [DOI: 10.1107/s0108767302097696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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