On the Small Enhancement of Electric Field Gradients Caused by a Deformation Potential Interaction : Condensed Matter and Statistical Physics

概要

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We examine the contribution of a deformation potential interaction to electric field gradients (EFG) and following quadrupole splitting (Q.S.) in the ground state through the comparison of EFG in the case of no deformation potential interaction, using Green function evaluated with the first order perturbation calculation. The potential V(R) and EFG are derived from the preceding Green function. From theoretical results, it is known that enhancement of EFG is caused by a deformation potential interaction and is proportional to the number of phonons around a conduction electron (= <N_<ph>>). The temperature dependence of V(R), as deduced from the thermal Green function, shows that the EFG increases with temperature. Experimentally, we apply these theoretical results to the Q.S. of a transition metaldoped β - FeSi_2, especially focusing on that of Co-doped β - FeSi_2. As a result, we obtain <N_<ph>> 〜 0.07 for Co-doped β - FeSi_2, which is relatively large in comparison with that for a typical covalent semiconductor. Compared with <N_<ph>> for a Ni-doped specimen, the effective mass of a conduction electron is considered to be relatively large in the Co-doped specimen.
理論物理学刊行会の論文
1998-11-25