Charge transfer process in Tl 2Ba 2Ca 2Cu 3O 10 and Tl 2Ba 2CaCu 2O 8 thin films probed by polarized X-ray absorption spectroscopy

Abstract

We report high-resolution polarized O 1s X-ray absorption spectra of highly c-axis-oriented Tl 2Ba 2Ca 2Cu 3O 10 (Tl-2223) and Tl 2Ba 2CaCu 2O 8 (Tl-2212) superconducting thin films. Near the O 1s edge, the low-energy pre-edge peak at 528.3 eV has mainly O 2p xy symmetry, while the pre-edge peak at 529.4 eV has predominantly O 2p z character. The spectral weight of the pre-edge peak at 528.3 eV, originating from the CuO 2 planes, increases ∼ 60% from the Tl-2212 to Tl-2223 thin films. Conversely, the high-energy pre-edge peak at 530.3 eV, originating from the TlO planes, is lower in spectral intensity by ∼ 30% in Tl-2223 as compared to the Tl-2212 thin film. The experimental results clearly demonstrate the pictures of the self doping due to the charge transfer from the CuO 2 layers to the TlO layers.