Frictional drag between quantum wells mediated by phonon exchange

Abstract

1998). Frictional drag between quantum wells mediated by phonon exchange. Physical Review B, 57(12), 7085-7102. DOI: 10.1103/PhysRevB.57.7085 Frictional drag between quantum wells mediated by phonon exchange We use the Kubo formalism to evaluate the contribution of acoustic-phonon exchange to the frictional drag between nearby two-dimensional electron systems. In the case of free phonons, we find a divergent drag rate ( D Ϫ1 ). However, D Ϫ1 becomes finite when phonon scattering from either lattice imperfections or electronic excitations is accounted for. In the case of GaAs quantum wells, we find that for a phonon mean free path l ph smaller than a critical value, imperfection scattering dominates and the drag rate varies as ln(l ph /d) over many orders of magnitude of the layer separation d. When l ph exceeds the critical value, the drag rate is dominated by coupling through an electron-phonon collective mode localized in the vicinity of the electron layers. We argue that the coupled electron-phonon mode may be observable for realistic parameters. Our theory is in good agreement with experimental results for the temperature, density, and d dependence of the drag rate.

Exchange and correlation effects on plasmon dispersions and Coulomb drag in low-density electron bilayers

“…[11][12][13][14][15][16][17] However, the phonon-mediated drag provides a dominant mechanism only in samples with large interlayer spacing where the absolute value of the measured drag rate is much smaller than that observed in these experiments. Moreover, the phonon mechanism is not supported by the measured density-ratio dependence of drag, which shows no peak at matched carrier densities in two layers, typical for that processes.…”

Optical-phonon-induced frictional drag in coupled two-dimensional electron gases

“…So far, the drag effects from both acoustic phonons 4,6 and plasmons 9 have been observed and studied theoretically. [11][12][13][14][15][16] Güven and Tanatar 17 studied the effect of optical phonons on plasmon-mediated drag. However, we are unaware of any work on direct optical-phonon-mediated drag.…”

“…It turns out that strong phase-space effects at particular energy and momentum transfers cause the acoustic phonons to dominate in spite of the weak coupling. 16 An obvious question arises: if the weak acoustic phonons give such a large contribution, can the optical phonons with a much larger coupling ͑witness the fact that scattering from optical phonons produces a much larger resistivity than scattering off their acoustic counterparts͒ give a correspondingly giant drag rate when they come in at higher temperatures?…”

“…Then, the explicit form for polar optical-phononmediated interaction is introduced, following the formalism for phonon-mediated drag given by Zhang and Takahashi 12 and Bo "nsager et al 16 …”

Virtual photon contribution to frictional drag in double-layer devices

“…Transresistance resulting from Coulomb drag depends on temperature as T 2 and decreases as d −4 in the distance between the wells. The theory was refined by including phonon exchange [4,5], which gave the main explanation of the observed deviations from the T 2 behaviour. A "current drag" effect was also proposed [6], and originates from the Van der Waals attraction between relative current flows.…”