Evolution of the electronic structure from the insulator to the superconductor in Bi2Sr2-xLax(Ca,Y)Cu2O8+d

TL;DR

This study investigates how the electronic structure of Bi2Sr2-xLax(Ca,Y)Cu2O8+d evolves from insulator to superconductor using photoemission spectroscopy, revealing a gradual shift of the lower Hubbard band with doping.

Contribution

It demonstrates the doping-dependent shift of the lower Hubbard band in Bi-based cuprates, highlighting differences from other cuprate families and advancing understanding of the insulator-superconductor transition.

Findings

Lower Hubbard band shifts upward with doping

Chemical potential shifts downward with hole doping

Behavior differs from LSCO cuprates

Abstract

La-doped and Y-doped Bi2Sr2CaCu2O8+d (Bi2212) compounds Bi2Sr2-xLax(Ca,Y)Cu2O8+d, which range from the insulator to the deeply underdoped superconductor, have been studied by angle-resolved photoemission spectroscopy. We have observed that the lower Hubbard band (LHB) of the parent insulator is gradually shifted upward with doping without significantly changing the band dispersions, which implies a downward shift of the chemical potential with hole doping. This behaviour is analogous to Bi2Sr2-xLaxCuO6+d (Bi2201) and Ca2-xNaxCuO2Cl2 (Na-CCOC) but is different from La2-xSrxCuO4 (LSCO), where the LHB stays well below the chemical potential and does not move while its intensity quickly diminishes in the underdoped region.