Evolution of the density of states at EF of Bi2-yPbySr2-xLaxCuO6+d and Bi2Sr2-xLaxCuO6+d cuprates with hole doping

TL;DR

This study investigates how the density of states at the Fermi level in Bi-based cuprate superconductors varies with hole doping, revealing a continuous increase in underdoped regions and saturation in overdoped regions, using X-ray and photo-emission spectroscopy.

Contribution

It provides a comparative analysis of occupied and unoccupied density of states across a wide doping range in Bi-based cuprates, highlighting the role of mobile holes in the CuO2 planes.

Findings

Density of states increases with doping in underdoped region.

Density of states saturates in overdoped region.

Mobile holes influence the prepeak intensity of O 1s absorption.

Abstract

Bi2Sr2-xLaxCuO6+d and Bi2-yPbySr2-xLaxCuO6+d high-Tc superconductors in a wide doping range from overdoped to heavily underdoped were studied by X-ray absorption and photo-emission spectroscopy. The hole concentration p was determined by an analysis of the Cu L3-absorption edge. Besides the occupied density of states derived from photoemission, the un-occupied density of states was determined from the prepeak of the O K-absorption edge. Both, the occupied as well as the unoccupied density of states reveal the same dependence on hole doping, i.e. a continuous increase with increasing doping in the hole underdoped region and a constant density in the hole overdoped region. By comparing these results of single-layer BSLCO with previous results on single-layer LSCO it could be argued that besides the localized holes on Cu sites the CuO2-planes consist of two types of doped holes, from which the so-called mobile holes determine the intensity of the prepeak of the O 1s absorption edge.