On Coulomb drag in double layer systems

Abstract

We argue, for a wide class of systems including graphene, that in the low temperature, high density, large separation and strong screening limits the drag resistivity behaves as d(-4), where d is the separation between the two layers. The results are independent of the energy dispersion relation, the dependence on momentum of the transport time, and the electronic wave function structure. We discuss how a correct treatment of the electron-electron interactions in an inhomogeneous dielectric background changes the theoretical analysis of the experimental drag results of Kim et al (2011 Phys. Rev. B 83 161401). We find that a quantitative understanding of the available experimental data (Kim et al 2011 Phys. Rev. B 83 161401) for drag in graphene is lacking.

Strong Coulomb drag and broken symmetry in double-layer graphene

“…2a and in the Supplementary Information. The T 2 dependence is expected for any interaction strength d/l between graphene layers [22][23][24][25][26][27][28] , provided that the carriers form a Fermi liquid state.…”

“…There are 4 distinct segments, which correspond to different combinations of electrons and holes in the two layers. If both layers contain carriers of the same (opposite) sign, ρ drag is negative (positive) [1][2][3][4][5][6][7][8][9][10][11][12][13][22][23][24][25][26][27][28] . The absolute value of ρ drag exhibits a maximum in each of the 4 segments at low carrier densities.…”

“…These features suggest a unique venue for searching for 1 new interaction phenomena. Accordingly, double-layer graphene has attracted significant theoretical interest and has already become a subject of intense debates about predictions for both Coulomb drag [22][23][24][25][26][27][28] and excitonic superfluidity 15,29 . As for experiment, a recent publication 16 reported Coulomb drag in double-layer graphene in zero magnetic field B by using devices in which the layers were separated by a several-nanometre-thick alumina barrier and had charge carrier mobilities µ ∼ 10,000 cm 2 V −1 s −1 .…”

Coulomb drag

“…As a result, the density dependence of ρ D (µ i v g /d) cannot be described by a power law. Partially due to this fact, several conflicting results for ρ D have been reported in literature (Amorim and Peres, 2012;Carrega et al, 2012;Hwang et al, 2011;Katsnelson, 2011;Lux and Fritz, 2012;Peres et al, 2011;Levitov, 2012, 2013;.…”

“…where the extra factor of 4 corresponds to extra degeneracy of Dirac fermions in graphene (Amorim and Peres, 2012;.…”