Pb0.4Bi1.6

Jian Ma

¹

,

P. Alméras

²

,

R. J. Kelley

³

et al.

Abstract

P b 0.4 Bi 1.6 Sr 2 CaCu 2 O 8+x (Bi(P b)−2212) single crystal samples were studied using transmission electron microscopy (TEM), ab−plane (ρ ab ) and c−axis

Evidence for a striped phase of high T c superconductor at the Fermi surface

“…The curvature of the white circles is drawn in such a way that they pass through the points where the photointensity is nearly half of the maximum intensity at the Fermi surface and the point (0.2π, π) where the maximum of the superconducting gap has been observed. The photointensity is very poor around the M point indicating a pseudogap the Fermi surface was indicated by Ma et al [14][15][16]. They reported a different nesting vector in the Γ − X(0.762π/a) versus Γ −Y (0.82π/a) in underdoped samples.…”

“…The polarization vector of the synchrotron light, the wave vector of the emitted photoelectron and the surface normal were kept in the same horizontal plane. In this geometry the horizontal plane plays the role of a plane of reflection symmetry (mirror plane) and dipole selection rules select initial states with even symmetry relative to it [11][12][13][14][15]23]. We have selected this polarization to have maximum emission intensity in the region of the pseudogap because transitions from initial states of b 1 (Cu 3d x 2 −y 2, O 2p x,y ) symmetry are allowed having even symmetry with respect to the mirror plane in the Γ − M − Z direction.…”

“…There is a general agreement on the presence of a large Fermi surface centered around the X and Y points with an extended Van Hove singularity at M = (π, 0) in the overdoped case [10][11][12][13][14][15][16][17][18]. On the other hand, underdoped samples [8][9][10]14] show a different Fermi surface with missing connecting segments near (π, 0) indicating a pseudogap. In this letter we report a global picture of the Fermi surface of an optimally doped Bi2212 system with T c = 91 K mapped by angle scanning technique.…”

“…Most of the ARPES work has been carried out on overdoped Bi2212 samples with a T c of 83-85 K [10][11][12][13][14][15][16][17][18] and recently on underdoped samples with T c of 10-83 K [8][9][10]14]. Lack of information on the Fermi surface at optimum doping, that corresponds to a T c of 91 K, is due to non availability of suitable single crystals.…”

“…Angle resolved photoemission spectroscopy (ARPES), which directly provides the momentum resolved one electron energy excitation spectral function, has been widely used to determine the Fermi surface properties of high T c materials [8][9][10][11][12][13][14][15][16][17][18]. However, the task of measurement of the Fermi surface is quite tedious by using the standard ARPES approach based on the measurement of several energy distribution curves (EDCs) at each emission angle to get a single point of the Fermi surface.…”