M. v. Zimmermann

Deutsches Elektronen-Synchrotron, Hamburg, Hamburg, Germany

Are you M. v. Zimmermann?

Claim your profile

Publications (101)224.34 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Underdoped high-temperature cuprate superconductors now appear to ubiquitously exhibit charge density wave (CDW) order. For hole doping near $^1/_8$ per planar copper atom, the CDW order develops above the superconducting transition temperature, $T_c$, and competes with the superconductivity below $T_c$. Experiments show that the modulations of the CDW order are aligned with both CuO directions in the CuO$_2$ planes with a period of 3-5 lattice spacings. However, the microscopic symmetry breaking corresponding to the CDW order has remained unclear. Here we use X-ray diffraction to determine the ionic displacements associated with the CDW order in the archetypical material YBa$_2$Cu$_3$O$_{7-x}$ (YBCO). We find that major components of the CDW are shear displacements perpendicular to the CuO$_2$ planes. These remove the mirror symmetry of the CuO$_2$ bilayers and have important implications for understanding the signals from other probes of the CDW order. For example, our results for the copper and oxygen displacement patterns give an explicit explanation of how signals described as "$s$- and/or bond $d$-density waves" can appear in scanning tunnelling microscopy (STM) and soft X-ray measurements. The CDW symmetry that we discover has implications for Fermi surface reconstruction observed by quantum oscillation (QO) measurements. Finally, we measure the $a/b$ anisotropy of the CDWs and find that the amplitudes of the $a$ and $b$-axis components are of the same order.
  • Source
    Nature Physics 03/2015; · 20.60 Impact Factor
  • Source
    Nature Physics 03/2015; DOI:10.1038/nphys3267 · 20.60 Impact Factor
  • Source
    Nature Physics 01/2015; · 20.60 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Low-dimensional electron systems, as realized naturally in graphene or created artificially at the interfaces of heterostructures, exhibit a variety of fascinating quantum phenomena with great prospects for future applications. Once electrons are confined to low dimensions, they also tend to spontaneously break the symmetry of the underlying nuclear lattice by forming so-called density waves; a state of matter that currently attracts enormous attention because of its relation to various unconventional electronic properties. In this study we reveal a remarkable and surprising feature of charge density waves (CDWs), namely their intimate relation to orbital order. For the prototypical material 1T-TaS2 we not only show that the CDW within the two-dimensional TaS2-layers involves previously unidentified orbital textures of great complexity. We also demonstrate that two metastable stackings of the orbitally ordered layers allow to manipulate salient features of the electronic structure. Indeed, these orbital effects enable to switch the properties of 1T-TaS2 nanostructures from metallic to semiconducting with technologically pertinent gaps of the order of 200 meV. This new type of orbitronics is especially relevant for the ongoing development of novel, miniaturized and ultra-fast devices based on layered transition metal dichalcogenides.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To explore the doping dependence of the recently discovered charge density wave (CDW) order in YBa2Cu3Oy, we present a bulk-sensitive high-energy x-ray study for several oxygen concentrations, including strongly underdoped YBa2Cu3O6.44. Combined with previous data around the so-called 1/8 doping, we show that bulk CDW order exists at least for hole concentrations (p) in the CuO2 planes of 0.078 <~ p <~ 0.132. This implies that CDW order exists in close vicinity to the quantum critical point for spin density wave (SDW) order. In contrast to the pseudogap temperature T*, the onset temperature of CDW order decreases with underdoping to T_CDW ~ 90K in YBa2Cu3O6.44. Together with a weakened order parameter this suggests a competition between CDW and SDW orders. In addition, the CDW order in YBa2Cu3O6.44 shows the same type of competition with superconductivity as a function of temperature and magnetic field as samples closer to p = 1/8. At low p the CDW incommensurability continues the previously reported linear increasing trend with underdoping. In the entire doping range the in-plane correlation length of the CDW order in b-axis direction depends only very weakly on the hole concentration, and appears independent of the type and correlation length of the oxygen-chain order. The onset temperature of the CDW order is remarkably close to a temperature T^\dagger that marks the maximum of 1/(T_1T) in planar 63^Cu NQR/NMR experiments, potentially indicating a response of the spin dynamics to the formation of the CDW. Our discussion of these findings includes a detailed comparison to the charge stripe order in La2-xBaxCuO4.
    Physical Review B 05/2014; 90(5). DOI:10.1103/PhysRevB.90.054514 · 3.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a volume-sensitive high-energy x-ray diffraction study of the underdoped cuprate high temperature superconductor La2-xSrxCuO4 (x = 0.12, Tc=27 K) in applied magnetic field. Bulk short-range charge stripe order with propagation vector q_ch = (0.231, 0, 0.5) is demonstrated to exist below T_ch = 85(10) K and shown to compete with superconductivity. We argue that bulk charge ordering arises from fluctuating stripes that become pinned near boundaries between orthorhombic twin domains.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The thermal decomposition of yttrium(III) valerate (Y(C4H9CO2)3) was studied in argon by means of thermogravimetry, differential thermal analysis, IR-spectroscopy, X-ray diffraction, in-situ synchrotron diffraction and hot-stage microscopy as well as room temperature optical microscopy. Melting takes place around 90 °C and evidence was found for solidification of the melt at 260 °C–300 °C, i.e. close to the onset of decomposition. Between 300 °C and 450 °C, Y(C4H9CO2)3 decomposes in a single step into Y2O2CO3 with release of gaseous CO2 and C4H9COC4H9 (5-nonanone). Final conversion to Y2O3 takes pace with release of CO2. The carbonaceous residue, which is left as a by-product during this last decomposition step is finally slowly burned by the residual oxygen present in the Ar atmosphere between 700 °C and 900 °C.
    Journal of Analytical and Applied Pyrolysis 03/2014; 106. DOI:10.1016/j.jaap.2014.01.009 · 3.07 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The thermal decomposition of La(C3H7CO2)3·xH2O (x ≈ 0.82) was studied in argon during heating at 5 K/min. After the loss of bound H2O, the anhydrous butyrate presents at 135 °C a phase transition to a mesophase, which turns to an isotropic liquid at 180 °C. The decomposition of the anhydrous butyrate is associated to a solidification process. The final decomposition to La2O3 takes place via two intermediate products: La2O(C3H7CO2)4 and La2O2CO3 with release of CO2 and the symmetrical ketone C3H7COC3H7.
    Thermochimica Acta 08/2013; 566:112–117. DOI:10.1016/j.tca.2013.05.016 · 2.11 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: X-ray diffraction measurements show that the high-temperature superconductor YBa_{2}Cu_{3}O_{6.54}, with ortho-II oxygen order, has charge-density-wave order in the absence of an applied magnetic field. The dominant wave vector of the charge density wave is q_{CDW}=(0,0.328(2),0.5), with the in-plane component parallel to the b axis (chain direction). It has a similar incommensurability to that observed in ortho-VIII and ortho-III samples, which have different dopings and oxygen orderings. Our results for ortho-II contrast with recent high-field NMR measurements, which suggest a commensurate wave vector along the a axis. We discuss the relationship between spin and charge correlations in YBa_{2}Cu_{3}O_{y} and recent high-field quantum oscillation, NMR, and ultrasound experiments.
    Physical Review Letters 03/2013; 110(13):137004. DOI:10.1103/PhysRevLett.110.137004 · 7.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a state-of-the-art x-ray diffraction study of the charge density wave order in 1T-TaS2 as a function of temperature and pressure. Our results prove that the charge density wave, which we characterize in terms of wave vector, amplitude and the coherence length, indeed exists in the superconducting region of the phase diagram. The data further imply that the ordered charge density wave structure as a whole becomes superconducting at low temperatures, i. e, superconductivity and charge density wave coexist on a macroscopic scale in real space. This result is fundamentally different from a previously proposed separation of superconducting and insulating regions in real space and, instead, provides evidence that the superconducting and the charge density wave gap exist in separate regions of reciprocal space.
    Physical review. B, Condensed matter 02/2013; 87(12). DOI:10.1103/PhysRevB.87.125135 · 3.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The effect of a magnetic field on the charge stripe order in La2−xBaxCuO4 has been studied by means of high-energy (100 keV) x-ray diffraction for charge carrier concentrations ranging from strongly underdoped to optimally doped. We find that charge stripe order can be significantly enhanced by a magnetic field applied along the c axis, but only at temperatures and dopings where it coexists with bulk superconductivity at zero field. The field also increases stripe correlations between the planes, which can result in an enhanced frustration of the interlayer Josephson coupling. Close to the famous x=1/8 compound, where zero field stripe order is pronounced and bulk superconductivity is suppressed, charge stripe order is independent of a magnetic field. The results for La2−xBaxCuO4 resemble recent observations in YBa2Cu3O6+δ and, independent of potential differences in the microscopic origin of charge order in these two compounds, imply a very similar competition with three-dimensionally coherent superconductivity.
    Physical Review B 01/2013; 87(1). DOI:10.1103/PhysRevB.87.014501 · 3.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The formation of the FeSe0.5Te0.5 phase was studied by means of high energy synchrotron x-ray diffraction. The precursors consisted of Fe, Se and Te or Se0.5Te0.5 powder mixtures and were encased in a metal (Cu/Nb) composite sheath to prevent evaporation of Se and Te during high temperature processing. In all cases (Fe - Se - Te ternary mixture; Fe - Se0.5Te0.5 binary mixtures with two different Fe particle sizes) the ternary alloy forms via Fe(Se,Te)(2) and Fe-3(Se,Te)(4) intermediate phases. When unreacted Se and Te powders are used in the precursor, partial Se1-xTex alloying takes place during heating prior and during the formation of the intermediate phases. As the alloying is incomplete, the resulting Fe(Se, Te) phase is not homogeneous. Using pre-alloyed Se0.5Te0.5 allows a better control of the reaction although homogeneisation also occurs in the Fe(Se, Te) phase as a consequence of the phase equilibria of the Se - Te system. The grain size of the starting Fe powder has no influence on the reaction path for the grain sizes used in the present study. However, the reaction rate for Fe(Se, Te) formation is clearly sensitive to this parameter. (C) 2012 Published by Elsevier B. V. Selection and/or peer-review under responsibility of the Guest Editors.
    12/2012; 36:600-605. DOI:10.1016/j.phpro.2012.06.175
  • [Show abstract] [Hide abstract]
    ABSTRACT: Resonant and nonresonant x-ray scattering studies on HoFe3(BO3)4 reveal competing magnetic ordering of Ho and Fe moments. Temperature and x-ray polarization dependent measurements employed at the Ho L3 edge directly reveal a spiral spin order of the induced Ho moments in the ab plane propagating along the c axis, a screw-type magnetic structure. At about 22.5 K the Fe spins are observed to rotate within the basal plane inducing spontaneous electric polarization, P. Components of P in the basal plane and along the c axis can be scaled with the separated magnetic x-ray scattering intensities of the Fe and Ho magnetic sublattices, respectively.
    Physical review. B, Condensed matter 12/2012; 86(22). DOI:10.1103/PhysRevB.86.224421 · 3.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: X-ray diffraction measurements show that the high-temperature superconductor YBa$_2$Cu$_3$O$_{6.54}$, with ortho-II oxygen order, has charge density wave order (CDW) in the absence of an applied magnetic field. The CDW has a 1-q structure with the in-plane component of the wavevector parallel to the $\mathbf{b}$-axis (chain direction), with a similar incommensurability to that observed in ortho-VIII and ortho-III samples, which have different dopings and oxygen orderings. Our results for ortho-II contrast with recent high-field NMR measurements, which suggest a commensurate wavevector along the $\mathbf{a}$-axis. We discuss the relationship between spin and charge correlations in YBa$_2$Cu$_3$O$_{y}$, and recent high-field quantum oscillation, NMR and ultrasound experiments.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The effect of a magnetic field on the charge stripe order in La(2-x)Ba(x)CuO(4) has been studied by means of high energy (100 keV) x-ray diffraction for charge carrier concentrations ranging from strongly underdoped to optimally doped. We find that charge stripe order can be significantly enhanced by a magnetic field applied along the c-axis, but only at temperatures and dopings where it coexists with bulk superconductivity at zero field. The field also increases stripe correlations between the planes, which can result in an enhanced frustration of the interlayer Josephson coupling. Close to the famous x=1/8 compound, where zero field stripe order is pronounced and bulk superconductivity is suppressed, charge stripe order is independent of a magnetic field. The results imply that static stripe order and three-dimensionally coherent superconductivity are competing ground states.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present an experimental study of the anisotropic resistivity of superconducting La2−xBaxCuO4 with x=0.095 and transition temperature Tc=32 K. In a magnetic field perpendicular to the CuO2 layers H⊥, we observe that the resistivity perpendicular to the layers ρ⊥ becomes finite at a temperature consistent with previous studies on very similar materials; however, the onset of finite parallel resistivity ρ∥ occurs at a much higher temperature. This behavior contradicts conventional theory, which predicts that ρ⊥ and ρ∥ should become finite at the same temperature. Voltage versus current measurements near the threshold of voltage detectability indicate linear behavior perpendicular to the layers, becoming nonlinear at higher currents, while the behavior is nonlinear from the onset parallel to the layers. These results, in the presence of moderate H⊥, appear consistent with superconducting order parallel to the layers with voltage fluctuations between the layers due to thermal noise. In search of uncommon effects that might help to explain this behavior, we have performed diffraction measurements that provide evidence for H⊥-induced charge- and spin-stripe order. The field-induced decoupling of superconducting layers is similar to the decoupled phase observed previously in La2−xBaxCuO4 with x=1/8 in zero field.
    Physical review. B, Condensed matter 04/2012; 85. DOI:10.1103/PhysRevB.85.134513 · 3.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present angle-resolved photoemission studies of (La{1-z}Pr{z}){2-2x}Sr{1+2x}Mn{2}O{7} with x=0.4 and z=0.1, 0.2, and 0.4 along with density functional theory calculations and x-ray scattering data. Our results show that the bilayer splitting in the ferromagnetic metallic phase of these materials is small, if not completely absent. The charge carriers are therefore confined to a single MnO{2} layer, which in turn results in a strongly nested Fermi surface. In addition to this, the spectral function also displays clear signatures of an electronic ordering instability well below the Fermi level. The increase of the corresponding interaction strength with z and its magnitude of ∼400  meV make the coupling to a bare phonon highly unlikely. Instead we conclude that fluctuating order, involving electronic and lattice degrees of freedom, causes the observed renormalization of the spectral features.
    Physical Review Letters 01/2012; 108(1):016403. DOI:10.1103/PhysRevLett.108.016403 · 7.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In situ synchrotron x-ray diffraction is used to study the phase and texture formation of ceria based films and superconductor films deposited by the chemical solution method on technical substrates. Combined analysis using in situ synchrotron x-ray diffraction, thermogravimetry/differential thermal analysis and Fourier transform infra-red (FTIR) spectroscopy allows to study the details on the decomposition and crystallization processes of ceria based in form of bulk and film. The success of this work demonstrates the possibility of studying chemical reaction pathway and texture evolution of oxides starting from solution precursors using non destructive method. (C) 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors.
    01/2012; 36:497-502. DOI:10.1016/j.phpro.2012.06.073
  • [Show abstract] [Hide abstract]
    ABSTRACT: The phase and texture formation of La doped CeO2 (CLO) films deposited by the chemical solution method are studied by in situ synchrotron x-ray diffraction. It is found that the CLO crystallites forms excellent in-plane texture as soon as the phase appears at 860°C, indicating that interfacial nucleation dominates at the beginning of the amorphous–crystallization transition. Grain growth is almost complete after at 900°C for 15min. Analysis of the isothermal process of crystallization at 900°C by the Johnson–Mehl–Avrami–Kolmogorov equation shows that grain development is mainly controlled by diffusion. The success of this work demonstrates the possibility of studying crystallization behaviors of solution derived films using a non-destructive method, which has the potential of being applicable to most types of thin film samples.
    Materials Letters 09/2011; 65(17):2669-2672. DOI:10.1016/j.matlet.2011.05.072 · 2.27 Impact Factor

Publication Stats

1k Citations
224.34 Total Impact Points

Institutions

  • 1995–2014
    • Deutsches Elektronen-Synchrotron
      • • Hamburger Synchrotronstrahlungslabor
      • • DESY Photon Science
      Hamburg, Hamburg, Germany
  • 2012
    • Technical University of Denmark
      • National Laboratory for Sustainable Energy
      Lyngby, Capital Region, Denmark
  • 1999–2001
    • Brookhaven National Laboratory
      • Physics Department
      New York City, NY, United States