Calculated acoustic plasmon spectra in GaSb, SnTe and Bi

Abstract

The authors present RPA calculations of the spectra of acoustic plasmons in GaSb, SnTe and Bi. They find that acoustic plasmons only just exist in Bi, having a small critical wavevector of about 10 mu m-1, beyond which they do not exist. In n-GaSb with 1.4*1024 electrons/m3, the calculations give an acoustic plasmon with velocity about 105 ms-1 and relative damping mod omega " mod / omega ' about 0.1. The acoustic plasmon exists for wavevectors up to at least 100 mu m-1 (where the RPA breaks down). In p-SnTe with 1.5*1026 holes/m3, they find an acoustic plasmon with velocity about 2*105 ms-1 and relative damping about 0.1. The spectrum ends abruptly at a critical wavevector which is about 100 mu m-1. They conclude that the prospects for observing acoustic plasmons are poor in Bi, but good in GaSb and SnTe.

Collective excitations and low-temperature transport properties of bismuth

“…21 (where V F s q and 2k F s were taken as energy and momentum units). Correspondingly, q * defines an energy and temperature scale,…”

“…The existence of acoustic plasmons was initially investigated for bismuth 21 by means of a simple spherical Fermi surface model with m s = m h = 0.14 and m r = m e = 0.047. Based on this approximation, it was concluded that the acoustic plasmon was very weak (k c = 0.02k F s ), although the authors also mentioned in their conclusion the issue of Fermi-surface elipticity.…”

“…A reminder is necessary: the masses which are substituted into (21) are not the ones given in Table I. Indeed, the masses in (21) are the ones along the external directions, while Table I gives the ellipsoid…”

“…We show that at low temperatures, a collective acousticplasmon mode exists 18 and plays a central role in the properties of the material. The existence of acoustic plasmon was studied before in the context of semimetals, [19][20][21] but not including the possible consequences of its existence. We discuss also the high-temperature regime of conductivity and show that the Baber mechanism 22 is the dominant source of resistivity in this regime.…”

Pairing from dynamically screened Coulomb repulsion in bismuth

“…It is also important to note that in the case of bismuth, where there are multiple Fermi surfaces with different Fermi velocities, there may exist an additional collective mode: the so called acoustic plasmon [32][33][34][35][36]. This mode has been considered as a possible mechanism for attractive interactions and superconductivity in semi-metals already a long time ago [33,[37][38][39][40][41].…”