P. Schlottmann

Florida State University, Tallahassee, Florida, United States

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Publications (204)482.39 Total impact

  • S. J. Yuan · S. Aswartham · J. Terzic · H. Zheng · H. D. Zhao · P. Schlottmann · G. Cao
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    ABSTRACT: Sr2IrO4 is a magnetic insulator assisted by strong spin-orbit coupling (SOC) whereas Sr2RuO4 is a p-wave superconductor. The contrasting ground states have been shown to result from the critical role of the strong SOC in the iridate. Our investigation of structural, transport, and magnetic properties reveals that substituting 4dRu4+(4d4) ions for 5dIr4+(5d5) ions in Sr2IrO4 directly adds holes to the t2g bands, reduces the SOC, and thus rebalances the competing energies in single-crystal Sr2Ir1−xRuxO4. A profound effect of Ru doping driving a rich phase diagram is a structural phase transition from a distorted I41/acd to a more ideal I4/mmm tetragonal structure near x=0.50 that accompanies a phase transition from an antiferromagnetic-insulating state to a paramagnetic-metal state. We also make a comparison with Rh-doped Sr2IrO4, highlighting important similarities and differences.
    No preview · Article · Dec 2015 · Physical Review B
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    ABSTRACT: Sr2IrO4 is a spin-orbit coupled insulator with an antiferromagnetic (AFM) transition at TN=240 K. We report results of a comprehensive study of single-crystal Sr2Ir1-xTbxO4. This study found that mere 3% (x=0.03) tetravalent Tb4+(4f7) substituting for Ir4+ (rather than Sr2+) completely suppresses the long-range collinear AFM transition but retains the insulating state, leading to a phase diagram featuring a decoupling of magnetic interactions and charge gap. The insulating state at x=0.03 is characterized by an unusually large specific heat at low temperatures and an incommensurate magnetic state having magnetic peaks at (0.95, 0, 0) and (0, 0.95, 0) in the neutron diffraction, suggesting a spiral or spin density wave order. It is apparent that Tb doping effectively changes the relative strength of the SOI and the tetragonal CEF and enhances the Hund's rule coupling that competes with the SOI, and destabilizes the AFM state. However, the disappearance of the AFM accompanies no metallic state chiefly because an energy level mismatch for the Ir and Tb sites weakens charge carrier hopping and renders a persistent insulating state. This work highlights an unconventional correlation between the AFM and insulating states in which the magnetic transition plays no critical role in the formation of the charge gap in the iridate.
    Full-text · Article · Nov 2015 · Physical Review B
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    S J Yuan · K Butrouna · J Terzic · H Zheng · S Aswartham · L E Delong · P Schlottmann · G Cao
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    ABSTRACT: BaIrO 3 is a magnetic insulator driven by the spin-orbit interaction (SOI), whereas BaRuO 3 is a paramagnet and exhibits a crossover from a metallic to an insulating regime. Our investigation of structural, magnetic, transport and thermal properties reveals that substitution of Ru 4+ (4d 4) ions for Ir 5+ (5d 5) ions in BaIrO 3 reduces the magnitudes of the SOI and a monoclinic structural distortion, and rebalances the competition between the SOC and the lattice degrees freedom to generate a rich phase diagram for BaIr 1-x Ru x O 3 (0  x  1). There are two major effects of Ru additions: (1) Light Ru doping (0 < í µí±¥ ≤ 0.15) prompts simultaneous, precipitous drops in both the magnetic ordering temperature T N and the electrical resistivity, which exhibits a crossover behavior from a metallic to an insulating state near T N. (2) Heavier Ru doping (0.41 ≤ í µí±¥ ≤ 0.9) induces a robust metallic state with a strong spin frustration generated by competing antiferromagnetic and ferromagnetic interactions.
    Full-text · Article · Oct 2015
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    ABSTRACT: BaIrO3 is a magnetic insulator driven by the spin-orbit interaction (SOI), whereas BaRuO3 is a paramagnet and exhibits a crossover from a metallic to an insulating regime. Our investigation of structural, magnetic, transport and thermal properties reveals that substitution of Ru4+ (4d4) ions for Ir5+ (5d5) ions in BaIrO3 reduces the magnitudes of the SOI and a monoclinic structural distortion, and rebalances the competition between the SOC and the lattice degrees freedom to generate a rich phase diagram for BaIr1-xRuxO3 (0< x <1). There are two major effects of Ru additions: (1) Light Ru doping (0 < x < 0.15) prompts simultaneous, precipitous drops in both the magnetic ordering temperature TN and the electrical resistivity, which exhibits a crossover behavior from a metallic to an insulating state near TN. (2) Heavier Ru doping (0.41< x < 0.9) induces a robust metallic state with a strong spin frustration generated by competing antiferromagnetic and ferromagnetic interactions.
    No preview · Article · Oct 2015
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    S J Yuan · S Aswartham · J Terzic · H Zheng · H D Zhao · P Schlottmann · G Cao
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    ABSTRACT: Sr 2 IrO 4 is a magnetic insulator assisted by strong spin-orbit coupling (SOC) whereas the Sr 2 RuO 4 is a p-wave superconductor. The contrasting ground states have been shown to result from the critical role of the strong SOC in the iridate. Our investigation of structural, transport, and magnetic properties reveals that substituting 4d Ru 4+ (4d 4) ions for 5d Ir 4+ (5d 5) ions in Sr 2 IrO 4 directly adds holes to the t 2g bands, reduces the SOC and thus rebalances the competing energies in single-crystal Sr 2 Ir 1-x Ru x O 4. A profound effect of Ru doping driving a rich phase diagram is a structural phase transition from a distorted I4 1 /acd to a more ideal I4/mmm tetragonal structure near x=0.50 that accompanies a phase transition from an antiferromagnetic-insulating state to a paramagnetic-metal state. We also make a comparison drawn with Rh doped Sr 2 IrO 4 , highlighting important similarities and differences.
    Full-text · Article · Sep 2015
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    S. J. Yuan · S. Aswartham · J. Terzic · H. Zheng · H. D. Zhao · P. Schlottmann · G. Cao
    [Show abstract] [Hide abstract]
    ABSTRACT: Sr2IrO4 is a magnetic insulator assisted by strong spin-orbit coupling (SOC) whereas the Sr2RuO4 is a p-wave superconductor. The contrasting ground states have been shown to result from the critical role of the strong SOC in the iridate. Our investigation of structural, transport, and magnetic properties reveals that substituting 4d Ru4+ (4d4) ions for 5d Ir4+(5d5) ions in Sr2IrO4 directly adds holes to the t2g bands, reduces the SOC and thus rebalances the competing energies in single-crystal Sr2Ir1-xRuxO4. A profound effect of Ru doping driving a rich phase diagram is a structural phase transition from a distorted I41/acd to a more ideal I4/mmm tetragonal structure near x=0.50 that accompanies a phase transition from an antiferromagnetic-insulating state to a paramagnetic-metal state. We also make a comparison drawn with Rh doped Sr2IrO4, highlighting important similarities and differences.
    Full-text · Article · Sep 2015
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    P. Schlottmann · A.A. Zvyagin
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    ABSTRACT: We consider the one-dimensional gas of fermions with spin S interacting via an attractive δ-function potential using the Bethe Ansatz solution. In zero magnetic field the atoms form bound states of fermions, i.e. generalized Cooper states with each atom having a different spin component. For low energy excitations the system is a Luttinger liquid and is properly described by a conformal field theory with conformal charge . The linear dispersion of a Luttinger liquid is asymptotically exact in the low-energy limit where the band curvature terms in the dispersion are irrelevant. For higher energy excitations, however, the spectral function displays deviations in the neighborhood of the single-particle (hole) energy, which can be described by an effective x-ray edge type model. Using the Bethe Ansatz solution we obtain expressions for the critical exponents for the single-particle (hole) Green's function. This model can be relevant in the context of ultracold atoms with effective total spin S confined to an elongated optical trap.
    Preview · Article · Jan 2015 · Nuclear Physics B
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    ABSTRACT: Here, we unveil evidence for a quantum phase-transition in CeCu_2Ge_2 which displays both an incommensurate spin-density wave (SDW) ground-state, and a strong renormalization of the quasiparticle effective masses (mu) due to the Kondo-effect. For all angles theta between an external magnetic field (H) and the crystallographic c-axis, the application of H leads to the suppression of the SDW-state through a 2^nd-order phase-transition at a theta-dependent critical-field H_p(theta) leading to the observation of small Fermi surfaces (FSs) in the paramagnetic (PM) state. For H || c-axis, these FSs are characterized by light mu's pointing also to the suppression of the Kondo-effect at H_p with surprisingly, no experimental evidence for quantum-criticality (QC). But as $H$ is rotated towards the a-axis, these mu's increase considerably becoming undetectable for \theta > 56^0 between H and the c-axis. Around H_p^a~ 30 T the resistivity becomes proportional T which, coupled to the divergence of mu, indicates the existence of a field-induced QC-point at H_p^a(T=0 K). This observation, suggesting FS hot-spots associated with the SDW nesting-vector, is at odds with current QC scenarios for which the continuous suppression of all relevant energy scales at H_p(theta,T) should lead to a line of quantum-critical points in the H-theta plane. Finally, we show that the complexity of its magnetic phase-diagram(s) makes CeCu_2Ge_2 an ideal system to explore field-induced quantum tricritical and QC end-points.
    Full-text · Article · Sep 2014 · Physical Review B
  • P Schlottmann · A A Zvyagin
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    ABSTRACT: In the context of ultracold fermionic atoms with effective spin S confined to an elongated trap we study the one-dimensional gas interacting via an attractive δ-function potential using the Bethe ansatz solution. There are N = 2S + 1 fundamental states: The particles can either be unpaired or clustered in bound states of 2, 3, ..., 2S and 2S + 1 atoms. In a magnetic field, the rich ground state phase diagram consists of these N states and various mixed phases in which combinations of the fundamental states coexist. The phase diagram simplifies considerably in zero-field, where only bound states of N atoms can exist. Due to the harmonic confinement and within the local density approximation, the density profile of bound states decreases along the tube from the center of the trap to its boundaries. In an array of tubes with weak Josephson tunneling superfluid order may arise. In zero-field the response functions determining the superfluid and density wave order are calculated using conformal field theory and the exact Bethe ansatz solution. The response function for superfluidity consists of a power law with distance, while the correlation function for density waves is a power law of distance times a sinusoidal factor oscillating with distance with a period given by two times the Fermi momentum. For S = 1/2 superfluidity is a possibility for all densities and density waves can be excluded. For S ≥ 3/2 superfluidity may occur at low densities but at high densities it gives way to density waves. We discuss the scenario of phase separation where for S ≥ 3/2 the system has superfluid long-range order toward the trap boundaries and density waves at its center.
    No preview · Article · Aug 2014 · Journal of Physics Conference Series
  • A. A. Zvyagin · P. Schlottmann
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    ABSTRACT: Motivated by recent experiments on ultracold fermions we study the effect of the spin-orbit interaction in an exactly solvable one-dimensional model with strong local attractive correlations between the fermions. We show that the asymptotes of correlation functions, calculated in the framework of the conformal field theory and finite size corrections of the Bethe ansatz exact solution, are strongly affected by the spin-orbit coupling. In the mixed phase, the correlation functions consist of terms that are the product of a power law of the distance and an oscillating function of the distance. We obtain the critical exponents for superfluidity and density waves. The leading exponents decrease as a function of spin-orbit coupling. In particular, the exponent for superfluidity is the smallest one signaling an instability to a phase where a weak interchain coupling can produce superfluidity of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) type. The spatial oscillation of the order parameter is also modified by the spin-orbit parameter, i.e., its modulation is not just given by the spin imbalance.
    No preview · Article · Nov 2013 · Physical Review B
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    ABSTRACT: We have observed a massive reconstruction of the Fermi surface of single crystal chromium as a function of high pressure and high magnetic fields caused by the spin-flip transition, with multiple new orbits appearing above 0.93 GPa. Additionally, some orbits have field-induced effective masses of ~0.06-0.07 me, seen only at high magnetic fields. Based on the temperature insensitivity displayed by the oscillation amplitudes at these frequencies, we attribute the orbits to quantum interference rather than to Landau quantization.
    Preview · Article · Jun 2013 · Physical review. B, Condensed matter
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    ABSTRACT: We observe an unusual combination of normal and superconducting state properties without any signature of strong spin fluctuations in single-crystal Ir3Te8. The electrical resistivity does not saturate by 700 K but exhibits a low-resistivity ratio, and it exhibits two extended linear regimes (approximately 20–330 and 370–700 K) with the same slope, separated by a small hysteretic interval marking a strong first-order phase transition from cubic to rhombohedral lattice symmetry at TS = 350 K. The electronic heat-capacity coefficient (11 mJ mol−1 K−2) is consistent with a net diamagnetic, rather than a Pauli paramagnetic, normal state that yields to superconductivity below a critical temperature TC = 1.8 K. The size of the heat-capacity jump near TC indicates bulk superconductivity.
    Full-text · Article · May 2013 · Physical review. B, Condensed matter
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    L. Li · P. P. Kong · T. F. Qi · C. Q. Jin · S. J. Yuan · L. E. DeLong · P. Schlottmann · G. Cao
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    ABSTRACT: Sr3Ir2O7 exhibits a novel Jeff=1/2 insulating state that features a splitting between Jeff=1/2 and 3/2 bands due to spin-orbit interaction. We report a metal-insulator transition in Sr3Ir2O7 via either dilute electron doping (La3+ for Sr2+) or application of high pressure up to 35 GPa. Our study of single-crystal Sr3Ir2O7 and (Sr1-xLax)3Ir2O7 reveals that application of high hydrostatic pressure P leads to a drastic reduction in the electrical resistivity by as much as six orders of magnitude at a critical pressure, PC = 13.2 GPa, manifesting a closing of the gap; but further increasing P up to 35 GPa produces no fully metallic state at low temperatures, possibly as a consequence of localization due to a narrow distribution of bonding angles {\theta}. In contrast, slight doping of La3+ ions for Sr2+ ions in Sr3Ir2O7 readily induces a robust metallic state in the resistivity at low temperatures; the magnetic ordering temperature is significantly suppressed but remains finite for (Sr0.95La0.05)3Ir2O7 where the metallic state occurs. The results are discussed along with comparisons drawn with Sr2IrO4, a prototype of the Jeff = 1/2 insulator.
    Full-text · Article · Apr 2013 · Physical review. B, Condensed matter
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    ABSTRACT: We observe superconductivity below a critical temperature TC = 1.8 K in single-crystal Ir3Te8, which also exhibits normal-state diamagnetism and a linear temperature dependence of electrical resistivity for a wide temperature interval, 20 K < T < 700 K. Single-crystal Ir3Te8 also undergoes a structural phase transition at TS = 350 K from a cubic (above TS) to a rhombohedral lattice below TS. Our first-principles electronic structure calculations reveal two bands crossing the Fermi level; despite the three-dimensional lattice, one band is quasi-two-dimensional, and is responsible for the observed diamagnetism and structure transition. The strong non-Fermi-liquid behavior characterized by the observed linearity in resistivity in such a nonmagnetic state suggests novel physics in this newly discovered superconductor.
    Full-text · Article · Jan 2013
  • J Hwang · E S Choi · F Ye · C R Dela Cruz · Y Xin · H D Zhou · P Schlottmann
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    ABSTRACT: We report the magnetic and electric properties of Ba$_3$NiNb$_2$O$_9$, which is a quasi-two-dimensional spin-1 triangular lattice antiferromagnet (TLAF) with trigonal structure. At low $T$ and with increasing magnetic field, the system evolves from a 120 degree magnetic ordering phase (A phase) to an up-up-down ($uud$) phase (B phase) with a change of slope at 1/3 of the saturation magnetization, and then to an "oblique" phase (C phase). Accordingly, the ferroelectricity switches on at each phase boundary with appearance of spontaneous polarization. Therefore, Ba$_3$NiNb$_2$O$_9$ is a unique TLAF exhibiting both $uud$ phase and multiferroicity.
    Preview · Article · Dec 2012 · Physical Review Letters
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    ABSTRACT: Sr2IrO4 is a magnetic insulator driven by spin-orbit interaction (SOI) whereas the isoelectronic and isostructural Sr2RhO4 is a paramagnetic metal. The contrasting ground states have been shown to result from the critical role of the strong SOI in the iridate. Our investigation of structural, transport, magnetic and thermal properties reveals that substituting 4d Rh4+ (4d5) ions for 5d Ir4+(5d5) ions in Sr2IrO4 directly reduces the SOI and rebalances the competing energies so profoundly that it generates a rich phase diagram for Sr2Ir1-xRhxO4 featuring two major effects: (1) Light Rh doping (0\leqx\leq0.16) prompts a simultaneous and precipitous drop in both the electrical resistivity and the magnetic ordering temperature TC, which is suppressed to zero at x = 0.16 from 240 K at x=0. (2) However, with heavier Rh doping (0.24< x<0.85 (\pm0.05)) disorder scattering leads to localized states and a return to an insulating state with spin frustration and exotic magnetic behavior that only disappears near x=1. The intricacy of Sr2Ir1-xRhxO4 is further highlighted by comparison with Sr2Ir1-xRuxO4 where Ru4+(4d4) drives a direct crossover from the insulating to metallic states.
    Full-text · Article · Sep 2012 · Physical Review B
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    T F Qi · O B Korneta · Xiangang Wan · L E DeLong · P Schlottmann · G Cao
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    ABSTRACT: We report an experimental/theoretical study of single-crystal Bi(2)Ir(2)O(7) that possesses a metallic state with strongly exchange-enhanced paramagnetism. The ground state of Bi(2)Ir(2)O(7) is characterized by the following features: (1) a divergent low-temperature magnetic susceptibility that indicates no long-range order down to 50 mK; (2) strongly field-dependent coefficients of the low-temperature T and T(3) terms of the specific heat; (3) a conspicuously large Wilson ratio R(W) ≈ 53.5; and (4) unusual temperature and field dependences of the Hall resistivity that abruptly change below 80 K, without any clear correlation with the magnetic behavior. All these unconventional properties suggest the existence of an exotic ground state in Bi(2)Ir(2)O(7).
    Full-text · Article · Jul 2012 · Journal of Physics Condensed Matter
  • P. Schlottmann · A. A. Zvyagin
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    ABSTRACT: In the context of ultracold atoms with effective spin S = 5/2 confined to an elongated trap we study the one-dimensional Fermi gas interacting via an attractive δ-function potential using the Bethe ansatz solution. There are N = 2S + 1 = 6 fundamental states: The particles can either be unpaired or clustered in bound states of 2, 3, …, 2S and 2S + 1 fermions. The rich ground state phase diagram consists of these six states and various mixed phases in which combinations of the fundamental states coexist. Possible scenarios for phase separation due to the harmonic confinement along the tube are explored within the local density approximation. In an array of tubes with weak Josephson tunneling superfluid order may arise. The response functions determining the type of superfluid order are calculated using conformal field theory and the exact Bethe ansatz solution. They consist of a power law with distance times a sinusoidal term oscillating with distance. The wavelength of the oscillations is related to the periodicity of a generalized Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state.
    No preview · Article · Jun 2012 · Modern Physics Letters B
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    J. M. Hwang · E. S. Choi · H. D. Zhou · Y. Xin · J. Lu · P. Schlottmann
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    ABSTRACT: We investigated the magnetic phase diagram of single crystals of SrNdFeO4 by measuring the magnetic properties, the specific heat and the dielectric permittivity. The system has two magnetically active ions, Fe3+ and Nd3+. The Fe3+ spins are antiferromagnetically ordered below 360 K with the moments lying in the ab plane, and undergo a reorientation transition at about 35–37 K to an antiferromagnetic order with the moments along the c axis. A short-range, antiferromagnetic ordering of Nd3+ along the c axis was attributed to the reorientation of Fe3+ followed by a long-range ordering at lower temperature [ Oyama et al. J. Phys.: Condens. Matter. 16 1823 (2004)]. At low temperatures and magnetic fields above 8 T, the Nd3+ moments are completely spin polarized. The dielectric permittivity also shows anomalies associated with spin configuration changes, indicating that this compound has considerable coupling between spin and lattice. A possible magnetic structure is proposed to explain the results.
    Preview · Article · Jun 2012 · Physical review. B, Condensed matter
  • P. Schlottmann · A. A. Zvyagin
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    ABSTRACT: In the context of a gas of ultracold atoms with effective spin S=3/2 confined to an elongated trap, we study the one-dimensional Fermi gas interacting via an attractive δ-function potential within the grand-canonical ensemble. The particles can be either unbound or clustered in bound states of two, three, and four fermions. The rich μ versus H ground-state phase diagram (μ is the chemical potential and H the external magnetic field) consists of the four basic states and the various possible mixed phases in which some these states coexist. Extending the analysis of K. Yang [ Phys. Rev. B 63 140511 (2001)] for S=1/2, we study the correlation functions of the generalized Cooper clusters of bound states of two, three, and four particles using conformal field theory and the exact Bethe Ansatz solution. The correlation functions consist of a power law with distance times a sinusoidal term oscillating with distance. In an array of tubes with weak Josephson tunneling, the type of superfluid order is determined by these correlation functions. The wavelength of the oscillations is related to the periodicity of a generalized Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state for higher spin particles. All the relevant states are analyzed for S=3/2.
    No preview · Article · May 2012 · Physical review. B, Condensed matter

Publication Stats

3k Citations
482.39 Total Impact Points

Institutions

  • 1991-2015
    • Florida State University
      • Department of Physics
      Tallahassee, Florida, United States
  • 2007-2011
    • University of Kentucky
      • Department of Physics & Astronomy
      Lexington, Kentucky, United States
  • 2005-2006
    • National High Magnetic Field Laboratory
      Tallahassee, Florida, United States
  • 2002
    • Northwest University
      Ch’ang-an, Shaanxi, China
  • 1987-1991
    • Temple University
      • Department of Physics
      Philadelphia, PA, United States
  • 1988
    • Tufts University
      • Department of Physics and Astronomy
      Бостон, Georgia, United States
  • 1979-1980
    • Freie Universität Berlin
      • Institute of Theoretical Physics
      Berlin, Land Berlin, Germany
  • 1972-1975
    • Max Planck Institute for Astrophysics
      Arching, Bavaria, Germany
  • 1973
    • Max Planck Institute for Physics
      München, Bavaria, Germany