# Evolution of the electronic structure from the insulator to the superconductor in Bi$_{2}$Sr$_{2}$$_{−}$$_{x}$La$_{x}$(Ca,Y)Cu$_{2}$O$_{8+}$$_{δ}$ 

K. Tanaka, 1 T. Yoshida, 1 K.M. Shen, 2 , 3 D.H. Lu, 2 W.S. Lee, 2 H. Yagi, 1 

A. Fujimori, 1 Z.-X. Shen, 2 Risdiana, 4 T. Fujii, 4 , 5 and I. Terasaki 4 

$^{1}$Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan 

$^{2}$Department of Applied Physics and Stanford Synchrotron Radiation Laboratory, Stanford University, Stanford, CA 94305, USA 

$^{3}$Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca NY 14853, USA 

$^{4}$Department of Applied Physics, Waseda University, Tokyo 169-8555, Japan 

$^{5}$Cryogenic Center, University of Tokyo, Bunkyo-ku, Tokyo 113-0032, Japan 

(Dated: October 29, 2018) 

## Abstract 

La-doped and Y-doped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+}$$_{δ}$ (Bi2212) compounds Bi$_{2}$Sr$_{2}$$_{−}$$_{x}$La$_{x}$(Ca,Y)Cu$_{2}$O$_{8+}$$_{δ}$, which range from the insulator to the deeply underdoped superconductor, have been studied by angle-resolved photoemission spectroscopy. We have observed that the lower Hubbard band (LHB) of the parent insulator is gradually shifted upward with doping without significantly changing the band dispersions, which implies a downward shift of the chemical potential with hole doping. This behaviour is analogous to Bi$_{2}$Sr$_{2}$$_{−}$$_{x}$La$_{x}$CuO$_{6+}$$_{δ}$ (Bi2201) and Ca$_{2}$$_{−}$$_{x}$Na$_{x}$CuO$_{2}$Cl$_{2}$ (Na-CCOC) but is different from La$_{2}$$_{−}$$_{x}$Sr$_{x}$CuO$_{4}$ (LSCO), where the LHB stays well below the chemical potential and does not move while its intensity quickly diminishes in the underdoped region. 

PACS numbers: 74.72.Hs, 79.60.-i, 71.30.+h 

