arXiv subjects

N. P. Armitage

Publications and source records attributed to N. P. Armitage.

148 records · Page 9Linked to original sources

arXiv2000

Fermi surface of Sr2RuO4 from angle resolved photoemission

We investigated the low-energy electronic structure of Sr2RuO4 by angle-resolved photoemission spectroscopy (ARPES) focusing, in particular, on the controversial issues of the Fermi surface (FS) topology and of the extended van Hove singularity (evHs). A detailed study of temperature and photon energy dependence demonstrates the surface-state nature of the electronic band responsible for the evHs, and may suggest the presence of ferromagnetic correlations at the surface. In addition, we detected a replica of the primary FS that indicates a (sqrt2 x sqrt2) surface reconstruction, as confirmed by LEED. In light of these findings, the FS determined by ARPES is consistent with LDA and de Haas-van Alphen (dHvA) results, and it provides additional information on the detailed shape of the alpha, beta and gamma sheets. Also, at this stage, because of the strong sensitivity of the cleaved surface, we could not find any robust signature of the crossover from 2D to 3D Fermi liquid behavior in our ARPES measurements for T<130 K.

cond-mat.str-el↗

arXiv2000

Superconducting Gap Anisotropy in Nd$_{1.85}$Ce$_{0.15}$CuO$_4$: Results from Photoemission

We have performed angle resolved photoelectron spectroscopy on the electron doped cuprate superconductor Nd$_{1.85}$Ce$_{0.15}$CuO$_4$. A comparison of the leading edge midpoints between the superconducting and normal states reveals a small, but finite shift of 1.5-2 meV near the ($π$,0) position, but no observable shift along the zone diagonal near ($π$/2,$π$/2). This is interpreted as evidence for an anisotropic superconducting gap in the electron doped materials, which is consistent with the presence of d-wave superconducting order in this cuprate superconductor.

cond-mat.supr-con↗

arXiv2000

Fermi Surface, Surface States, and Surface Reconstruction in Sr2RuO4

The electronic structure of Sr2RuO4 is investigated by high angular resolution ARPES at several incident photon energies. We address the controversial issues of the Fermi surface (FS) topology and of the van Hove singularity at the M point, showing that a surface state and the replica of the primary FS due to (sqrt2 x sqrt2) surface reconstruction are responsible for previous conflicting interpretations. The FS thus determined by ARPES is consistent with the de Haas-van Alphen results, and it provides additional information on the detailed shape of the alpha, beta and gamma sheets.

cond-mat.str-el↗

arXiv2000

n(k) Structure and Matrix Elements in Photoemission: Results from Insulating Ca_2CuO_2Cl_2

The photon energy dependence of angle-resolved photoemission data on Ca_2CuO_2Cl_2 is presented, and the role of the matrix element is investigated. It is shown that despite strong variations in the matrix element, the loss in intensity as one crosses the antiferromagnetic zone boundary is a robust feature of the Mott insulator. As expected for a two dimensional system, the dispersion remains independent of the photon energy even when the matrix element does not.

cond-mat.str-el↗