Recardo Manzke - Academia.edu (original) (raw)

Papers by Recardo Manzke

Physica C: Superconductivity, 1989

Photoemission spectra taken at room temperature with high energy and angle resolution on Bi2Sr2Ca... more Photoemission spectra taken at room temperature with high energy and angle resolution on Bi2Sr2CaCu2O8 single crystals reveal a band near EF with weak dispersion along lambdaX. It crosses EF at about 1/2 lambdaX and the occupied part becomes visible up to the Brillouin zone boundary in angle-resolved inverse photoemission spectra. Starting for T&gt;Tc with a clear Fermi edge, for T&lt;Tc

Femtosecond optical reflectivity measurements of La2-xSrxCuO4, La2CuO4+y, Bi2Sr2CuO6+z and Bi2Sr2... more Femtosecond optical reflectivity measurements of La2-xSrxCuO4, La2CuO4+y, Bi2Sr2CuO6+z and Bi2Sr2CaCu2O8+delta thin films and single crystal samples indicate qualitative changes with fluence. At the lowest fluencies, there is a power law divergence in the relaxation time. The divergence has an onset temperature of 55+/-15K, independent of whether the sample is in the superconducting or normal states. At slightly higher fluencies, still

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2012

ABSTRACT A new 5-m normal-incidence monochromator at the third generation synchrotron source BESS... more ABSTRACT A new 5-m normal-incidence monochromator at the third generation synchrotron source BESSY II of the Helmholz-Zentrum Berlin (HZB) has been constructed with the emphasis on angle-resolved photoelectron spectroscopy with high-resolution and at low energy utilizing photons from 5 eV to 40 eV. Optical design and preliminary performance results of the beamline and the photoemission endstation are presented and match the design goals.

Superconducting and Related Oxides: Physics and Nanoengineering V, 2002

Surface Science, 1992

Abstract High-resolution angle-resolved photoemission performed on cleaved surfaces of twinned YB... more Abstract High-resolution angle-resolved photoemission performed on cleaved surfaces of twinned YBa 2 Cu 3 O 7−δ single crystals at 20 K revealed an intrinsic surface-derived electronic state for this high-temperature superconductor. In the spectra it is very pronounced around the X(Y) point of the Brillouin zone where its binding energy is 0.92 eV. It shows slight k ∥ -, no k ⊥-dispersion , and a strong sensitivity to surface contamination. The existence of this state points to a rearrangement of electron charge in the surface layers and consequences for the superconducting behaviour on the surface of 1:2:3 superconductors will be discussed.

$Research paper thumbnail of Charge-Density-Wave Phase of 1T-TiSe_{2}: The Influence of Conduction Band Population$

Physical Review Letters, 2011

Physical Review Letters, 2009

ABSTRACT A Comment on the Letter by J. Wei et al., [Phys Rev. Lett. 101, 097005 (2008)]. The auth... more ABSTRACT A Comment on the Letter by J. Wei et al., [Phys Rev. Lett. 101, 097005 (2008)]. The authors of the Letter offer a Reply.

$Research paper thumbnail of Electronic structure of ZrS_{x}Se_{2−x} by Tran-Blaha modified Becke-Johnson density functional$

Physical Review B, 2011

Page 1. PHYSICAL REVIEW B 84, 125205 (2011) Electronic structure of ZrSxSe2−x by Tran-Blaha modif... more Page 1. PHYSICAL REVIEW B 84, 125205 (2011) Electronic structure of ZrSxSe2−x by Tran-Blaha modified Becke-Johnson density functional A. Ghafari,1,* A. Boochani,2 C. Janowitz,1 and R. Manzke1 1Institut für Physik, Humboldt ...

Physical Review B, 2009

Single crystals of layered transition-metal dichalcogenide compounds of ZrS x Se 2− x with compos... more Single crystals of layered transition-metal dichalcogenide compounds of ZrS x Se 2− x with composition 0≤ x≤ 2 were grown by the chemical-vapor-transport technique and characterized with the help of different methods. Indirect gap transitions with remarkably ...

Physical Review B, 2004

ABSTRACT The band gaps of HfS2 (1.96 eV) and HfSe2 (1.13 eV) cover the range of ideal band gaps f... more ABSTRACT The band gaps of HfS2 (1.96 eV) and HfSe2 (1.13 eV) cover the range of ideal band gaps for photovoltaic applications which is for a single-junction cell about 1.45 eV and for a two-junction cell about 1.1 eV and 1.8 eV. Additionally, in favor of applications the transition-metal dichalcogenides have a strong tendency to grow as thin films due to their quasi-two-dimensional character. Employing the chemical vapor transport method, single crystals of this ternary semiconductor were grown with nine different compositions. They were characterized in detail by low-energy electron diffraction, Laue diffraction, and energy dispersive x-ray analysis. In addition the absorption at room temperature was measured, revealing an absorption coefficient alpha(hnu) that is remarkably high for an indirect semiconductor. The determined band gaps of HfSxSe2-x show a nearly linear dependence on x, which is perfect for band-gap engineering. Furthermore, in the gap an exponential behavior of alpha(hnu) is observed, which could be interpreted as an Urbach tail.

Physica C: Superconductivity, 2004

Physica C: Superconductivity, 1991

Journal of Physics: Conference Series, 2009

Abstract. The exact shape of the superconducting dome in the Bi-cuprates depends on the proper de... more Abstract. The exact shape of the superconducting dome in the Bi-cuprates depends on the proper determination of the hole content in the CuO2 layers. Single crystals of Bi (Pb)-2201 were studied over a wide doping range from the overdoped to the heavily underdoped regime by x-ray absorption spectroscopy (XAS) in order to determine the hole content of the compounds. By analysing the Cu-LIII edge this technique proved to be successful for polycrystalline oxide-based high-Tc superconductors, while for single crystals an ...

Journal of Electron Spectroscopy and Related Phenomena, 2011

Journal of Electron Spectroscopy and Related Phenomena, 2013

ABSTRACT Angle-resolved photoelectron spectroscopy using synchrotron radiation has been performed... more ABSTRACT Angle-resolved photoelectron spectroscopy using synchrotron radiation has been performed on 1T–ZrSxSe2−x, where x varies from 0 to 2, in order to study the influence of the spin-orbit interaction in the valence bands. The crystals were grown by chemical vapour transport technique using Iodine as transport agent. A characteristic splitting of the chalcogen p-derived valence bands along high symmetry directions has been observed experimentally. The size of the splitting increases with the increase of the atomic number of the chalcogenide, e.g. at the A point of the Brillouin zone from 0.06 eV to 0.31 eV with an almost linear dependence with x, as progressing from ZrS2 towards ZrSe2, respectively. Electronic structure calculations based on the density functional theory have been performed using the model of Tran–Blaha [1] and the modified version of the exchange potential proposed by Becke and Johnson [2] (TB–MBJ) both with and without spin-orbit (SO) coupling. The calculations show that the splitting is mainly due to spin-orbit coupling and the degeneracy of the valance bands is lifted.

Journal of Alloys and Compounds, 2007

ABSTRACT Electrical transport studies have been carried out on single crystals of metallic MoTe2.... more ABSTRACT Electrical transport studies have been carried out on single crystals of metallic MoTe2. Temperature-dependent electrical resistivity, ρ(T)−ρ(0), was found proportional to T2 up to 50 K. The magneto-resistance measurements showed the normal characteristics of a metal, the Hall coefficient has a strong dependence on the temperature.

Applied Physics Letters, 2010

beta-Ga2O3 has the widest energy gap of the transparent conducting oxides. The interest in its el... more beta-Ga2O3 has the widest energy gap of the transparent conducting oxides. The interest in its electronic properties has recently increased because of its applications in various optoelectronic devices, semiconductor lasers, and ultrasensitive gas detecting systems. In contrast, information on the electronic structure of beta-Ga2O3 is very scarce. Here, we present the experimental valence-band structure of beta-Ga2O3 single crystals determined by

arXiv preprint arXiv:1111.6205, Nov 27, 2011

Abstract: LaFe3/4Ni1/4O3 was subjected to oxygen near edge x-ray absorption fine structure (NEXAF... more Abstract: LaFe3/4Ni1/4O3 was subjected to oxygen near edge x-ray absorption fine structure (NEXAFS) spectroscopy for 300 K< T< 773 K. The spectra show in the pre-edge a small hole doped peak originating from Ni substitution. The relative spectral weight of this transition to the weight of the hybridized O (2p)-Fe (3d) transitions scales with T and has a maximum at around 600 K. The characteristic energies of the thermal activated spectral intensity and conductivity suggest that the concentration of charge transferred electrons from O (2p) to ...

EPL (Europhysics Letters), 2016

The near-E F band of the in situ cleaved (111) surface of high-quality n-type In2O3 single crysta... more The near-E F band of the in situ cleaved (111) surface of high-quality n-type In2O3 single crystals was investigated by high-resolution angle-resolved photoemission (ARPES) along the major symmetry lines of the three-dimensional Brillouin zone. Several criteria to pin down Fermi level crossings and Fermi momenta were applied. The near-E F band is of three-dimensional character connected to the bottom of the conduction band. Since the model of a degenerate semiconductor due to high n-type doping is not sufficient the interaction of electron and phonon degrees of freedom is discussed. It is found that the model of Landau-Pekar polarons is capable of describing the observed lineshape qualitatively and the bandwidth of the occupied part of the conduction band quantitatively.

Applied Surface Science, 2016

Abstract The electronic structure of the ternary layered transition metal dichalcogenide compound... more Abstract The electronic structure of the ternary layered transition metal dichalcogenide compounds of ZrS x Se 2− x , where 0 ≤ x ≤ 2, has been studied by means of high resolution angle-resolved photoemission spectroscopy (ARPES) used in conjunction with synchrotron radiation facilities. The crystals were grown by the chemical vapor transport technique using iodine as a transport agent. They are found to be degenerate extrinsic n -type semiconductors with an indirect bandgap character. The experimental valence band structure of the complete series of ZrS x Se 2− x is reported along the major symmetry azimuthal directions in the Brillouin zone parallel to the layers. The results show that the binding energies of the topmost valence band shift almost linearly with the composition parameter x . Further, an emission from the conduction band minimum observed just below the Fermi edge enabled us to estimate the energy gap values. The electronic structure deduced from the photoemission measurements are discussed and compared to band structure calculations.