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Z. X. Shen

Publications and source records attributed to Z. X. Shen.

60 records · Page 4Linked to original sources
arXiv2003

Temperature Dependence of Resistivity of $Sr_2CoMoO_{6-δ}$ Films

We investigate the temperature dependence of the resistivity and magnetoresistance of a polycrystalline $Sr_2CoMoO_{6-δ}$ film deposited on (100)-$SrTiO_3$ substrate prepared by the pulsed laser deposition method. X-ray diffraction, Raman and magnetoresistance results demonstrate clearly the coexistence of a ferromagnetic metallic and an antiferromagnetic (or paramagnetic) insulating domain. Percolative transition between these two phases as the temperature varies, which is believed to induce a metal-insulator transition at around $T_C$, has been directly observed in our measurements of the temperature dependence of the sample resistivity. Thus we have provided new direct evidence that a phase separation scenario also exists in the ordered double-perovskite structure materials.

cond-mat.mtrl-sci↗
arXiv2001

ARPES study of Pb doped Bi_2Sr_2CaCu_2O_8 - a new Fermi surface picture

High resolution angle resolved photoemission data from Pb doped Bi_2Sr_2CaCu_2O_8 (Bi2212) with suppressed superstructure is presented. Improved resolution and very high momentum space sampling at various photon energies reveal the presence of two Fermi surface pieces. One has the hole-like topology, while the other one has its van Hove singularity very close to (pi,0), its topology at some photon energies resembles the electron-like piece. This result provides a unifying picture of the Fermi surface in the Bi2212 compound and reconciles the conflicting reports.

cond-mat.str-el↗
arXiv2001

Evidence of Electron Fractionalization from Photoemission Spectra in the High Temperature Superconductors

In the normal state of the high temperature superconductors Bi_2Sr_2CaCu_2O_{8+delta} and La_{2-x}Sr_{x}CuO_4, and in the related ``stripe ordered'' material La_1.25Nd_0.6Sr_0.15CuO_4, there is sharp structure in the measured single hole spectral function A(k,w) considered as a function of k at fixed small binding energy w. At the same time, as a function of w at fixed k on much of the putative Fermi surface, any structure in A(k,w), other than the Fermi cutoff, is very broad. This is characteristic of the situation in which there are no stable excitations with the quantum numbers of the electron, as is the case in the one dimensional electron gas.

cond-mat.supr-con↗
arXiv2000

Evidence for an energy scale for quasiparticle dispersion in Bi_2Sr_2CaCu_2O_8

Quasiparticle dispersion in $Bi_{2}Sr_{2}CaCu_{2}O_{8}$ is investigated with improved angular resolution as a function of temperature and doping. Unlike the linear dispersion predicted by the band calculation, the data show a sharp break in dispersion at $50\pm10$ $meV$ binding energy where the velocity changes by a factor of two or more. This change provides an energy scale in the quasiparticle self-energy. This break in dispersion is evident at and away from the d-wave node line, but the magnitude of the dispersion change decreases with temperature and with increasing doping.

cond-mat↗
arXiv2000

Photoemission Studies on Bi2Sr2CaCuZnO - Electronic Structure Evolution and Temperature Dependence

An angle resolved photoelectron spectroscopy study was conducted on BiSrCaCuZnO. A small amount of Zn substitution for Cu almost completely suppresses the otherwise sharp spectral peak along the (0,0) to (pi,pi) direction in BiSrCaCuZnO, while superconductivity with Tc as high as 83K survives. This behavior contrasts markedly from that seen in cases where the impurities are located off the CuO plane, as well as when the CuO planes are underdoped. This effect is also accompanied by changes of low energy excitations at (pi,0), near the anti-node position of the d-wave pairing state. With Zn doping the size of the superconducting gap is significantly suppressed, the width of the quasiparticle peak in the superconducting state becomes wider, and the dip at higher binding energy is diminished. In addition, enhanced temperature induced spectral changes also occur. We show intriguing systematic lineshape changes with temperature that persist to a very high energy scale - a result consistent with the idea that Zn enhances the local charge inhomogeneity.

cond-mat.supr-con↗