Angle-resolved photoemission spectroscopy of band tails in doped semiconductors
thesisposted on 04.07.2018 by Kimberley Reynolds
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
A theory of angle-resolved photoemission (ARPES) in doped semiconductors is developed, paying particular attention to ARPES of the impurity band. We derive the ARPES spectra for impurity band tails, taking into consideration various positions of the valence band maximum on the Brillouin zone. On the basis of our theory, we have provided a detailed analysis on the ARPES of semiconductors and have proposed explanations for several features of the ARPES spectra taken from the cuprate superconductors. These include sharp "quasi-particle" peaks, rapid loss of their intensities in some directions of the Brillouin zone ("Fermi arcs") and the high energy waterfall, which we propose is a consequence of matrix-element effects of disorder-localised band-tails in the charge transfer gap of doped Mott-Hubbard insulators. Our theory proposes that the ARPES intensity of cuprates near (π/2a, π/2a) is proportional to the square of the Fourier transform component of the impurity wave-function. Our real space image reveals some band mass anisotropy and predicts the size of the localised state of about 10 to 20 lattice constants which justifies the "envelope" approximation used in the impurity wave-function.