We have measured photoemission spectra of SrTiO3/LaTiO3 superlattices with a topmost SrTiO3 layer of variable thickness. Finite coherent spectral weight with a clear Fermi cut-off was observed at chemically abrupt SrTiO3/LaTiO3 interfaces, indicating that an ``electronic reconstruction'' occurs at the interface between the Mott insulator LaTiO3 and the band insulator SrTiO3. For SrTiO3/LaTiO3 interfaces annealed at high temperatures (~ 1000 C), which leads to Sr/La atomic interdiffusion and hence to the formation of La1-xSrxTiO3-like material, the intensity of the incoherent part was found to be dramatically reduced whereas the coherent part with a sharp Fermi cut-off is enhanced due to the spread of charge. These important experimental features are well reproduced by layer dynamical-mean-field-theory calculation.
@article{arxiv.cond-mat/0604201,
title = {Photoemission from buried interfaces in SrTiO3/LaTiO3 superlattices},
author = {M. Takizawa and H. Wadati and K. Tanaka and M. Hashimoto and T. Yoshida and A. Fujimori and A. Chikamtsu and H. Kumigashira and M. Oshima and K. Shibuya and T. Mihara and T. Ohnishi and M. Lippmaa and M. Kawasaki and H. Koinuma and S. Okamoto and A. J. Millis},
journal= {arXiv preprint arXiv:cond-mat/0604201},
year = {2009}
}