Abstract
The presence of several kinds of carriers at the Fermi surface results in interesting complex dielectric properties of the bulk Pd in the low-energy excitation range. A most spectacular manifestation of this is the presence of a collective electronic excitation characterized by a soundlike dispersion, termed acoustic plasmon (AP). Due to the characteristic dispersion reaching zero energy in the long-wavelength limit, the question of the thermal stability of the excitation spectrum arises. In this work we explore this problem investigating the thermal effect on the electronic excitation spectrum in this material, tracing how the AP properties vary with the temperature increase. The main effect consists in the gradual destruction of AP in the energy range corresponding to the temperature.
Highlights
In metallic systems the Fermi surface crossing by several energy bands with different Fermi velocities may result in a strong modification of dielectric properties as compared with those obtained for simple metals within a model of the homogeneous electron gas
In this work we explore this problem investigating the thermal effect on the electronic excitation spectrum in this material, tracing how the acoustic plasmon (AP) properties vary with the temperature increase
A simplified theory like those employed for the description of collective electronic excitation in the near-free electron-gas systems cannot provide a definite proof of existence of AP in metals
Summary
In metallic systems the Fermi surface crossing by several energy bands with different Fermi velocities may result in a strong modification of dielectric properties as compared with those obtained for simple metals within a model of the homogeneous electron gas. A collective excitation in which the slow carriers are dynamically screened by the fast ones can be realized [2] Such a mode has a soundlike dispersion similar to that of the acoustic phonons, i.e., its energy decreases linearly to zero as the momentum goes to zero. The detailed numerical calculations taking fully into account the realistic band structure predicted such kind of collective excitation in a variety of metal systems possessing several kinds of bulk carriers at the Fermi surface It was predicted in elemental metals Pd [15,16] and Pb [17] and some layered materials like MgB2 [18], intercalated graphite
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