model to calculate the photoemission spectra (PES) of a doped simple cubic lattice.

We mean to investigate the two intrinsic attributes of electrons: itineracy and

localization, which is able to clarify the co-existence of a Fermi edge and the step-like

multi-phonon structure, observed recently in the PES experiment of the boron-doped

diamond (BDD). Focusing on the area close to the Fermi level, a simple cubic lattice

structure is adopted instead of the real diamond one to simulate the various valence

band nature of BDD. This can simplify the problem without losing the key point.

For the phonon effect becomes significant just after the doping, we take into

account the electron-phonon (e-ph) coupling only at the doped sites. However, the

phonon effect is then not very noticeable after averaging all the sites, so we also

calculate the spectrum of doped sites only, beside the whole system spectrum. From

the classical Monte Carlo (MC) computation, the emergence of a clear Fermi edge is

seen. increasing the doping ratio, the impurity band expands upto the top of valence

band, and fills the small semiconductor gap gradually. Thus, the sample undergoes a

semiconductor-metal transition. Electrons can move freely from one impurity atom to

another one through those intermediate carbon atoms. In quantum MC simulations,

the lattice Green's function is calculated by the path-integral theory to reproduce the

spectral function. From the whole system spectra, the phase transition is confirmed on

the increase of the dopant concentration. The satellite structure is observed in the

doped sites spectrum, even within lightly doped sample. This structure has not been

found in classical MC cases, obviously coming from the phonon quantum character in

the e-ph coupling. Increasing the coupling constant, a second phonon peak also

presents corresponding to the double-phonon, even multi-phonon scattering process.

Because of the stronger coupling, a clear Fermi edge also appears although the doping

rate is low. The co-existence of a Fermi edge and the step-like multi-phonon satellite

structure is reproduced completely, which can be interpreted from the two basic

properties of electrons: itineracy and localization.

At the same time, our method, which can distinguish the spectra of different

components in the material as we have done in calculating the spectra for the whole

system and the doped sites only respectively, is very useful-to study the doped

systems, and to explain the resonant PES experiments., 総研大甲第1094号}, title = {Photoemission Spectra Calculation of Boron-Doped Diamond using Quantum Monte Carlo Method}, year = {} }