Superconducting Gap in Bi-Sr-Ca-Cu-O by High-Resolution Angle-Resolved Photoelectron Spectroscopy

Abstract

Detailed studies indicate a superconducting gap in the high-temperature superconductor Bi(2)Sr(2)CaCu(2)O(8). Photoemission measurements with high energy and angle resolution isolate the behavior of a single band as it crosses the Fermi level in both the normal and superconducting states, giving support to the Fermi liquid picture. The magnitude of the gap is 24 millielectron volts.

Doping dependence of the chemical potential in cuprate high-Tc superconductors I. La2−xSrxCuO4

“…With this technique no density of states is found near the Fermi energy E F for the parent insulating materials, whereas for the doped metallic samples a clear Fermi level is present in the measurements [1,2], proving the fermionic character of the states near E F . Another important result obtained with photoelectron spectroscopy is that angle resolved measurements indicate a Fermi surface that agrees well in size and shape with predictions of band structure calculations [3][4][5][6][7]. This agreement is remarkable, because in these calculations the correlations between the electrons is generally neglected.…”

Hole pockets in thet-Jmodel

“…Let us next discuss experimental results on hightemperature superconductors assuming that the hole pockets found in the cluster studies persist in the real systems. The volume of the FS associated with the Cu − O plane-derived bands in these materials presents a well-known puzzle: early photoemission experiments [18] show bands, which disperse towards the Fermi energy and vanish at points in k-space which are roughly located on the free electron FS corresponding to electron density 1 − δ, where δ is the hole concentration; on the other hand transport properties can be modelled well [19,20] by assuming a FS with a volume ∼ δ. In a Fermi liquid, the apparently contradicting quantities actually fall into distinct classes: photoemission spectra depend on Z h , transport properties do not.…”

Evidence for a strong impact of the electron-photon matrix element on angle-resolved photoelectron spectra of layered cuprate compounds

“…Examples of results obtained by ARPES are the existence of a Fermi surface in the normal state compatible with the Luttinger theorem 1-3 and the observation of the superconducting gap and its anisotropy as well as a gap in the normal state in the underdoped regime. [4][5][6] One of the appealing features of ARPES is that the spectral intensity of an electron distribution curve ͑EDC͒ is directly proportional to the electron-photon matrix element weighted spectral function. 7 Direct insight into the spectral function can therefore be gained, which currently is not possible with any other experimental method.…”