Available online at www.sciencedirect.com Physica E 18 (2003) 165–166 www.elsevier.com/locate/physe Dynamical correlations in Coulomb drag eect B.Tanatar a ; ∗ ,B.Davoudi b ,B.Y.-K.Hu c a Department of Physics, Bilkent University, 06533 Ankara, Turkey b NEST-INFM and Classe di Scienze, Scuola Normale Superiore, I-56126 Pisa, Italy c Department of Physics, University of Akron, Akron, OH 44325-4001, USA Abstract MotivatedbyrecentCoulombdragexperimentsinpairsoflow-densitytwo-dimensional(2D)electrongases,weinvestigate the inuence of correlation eects on the interlayer drag rate as a function of temperature. We use the self-consistent eld method to calculate the intra and interlayer local-eld factors Gij (q; T ) which embody the short-range correlation eects. We calculate the transresistivity using the screened eective interlayer interactions that result from incorporating these local-eld factors within various approximation schemes. Our results suggest that dynamic (frequency dependent) correlations play an important role in enhancing the Coulomb drag rate. ? 2003 Elsevier Science B.V. All rights reserved. Keywords: Coulomb drag eect; Correlations; Eective interactions There has been extensive theoretical and experimental activity on the frictional drag in coupled quantum-well sys- temsinrecentyears[1].Thedrageectoriginates[2,3]from the interlayer Coulomb interactions between two spatially separated electron systems. When a current I is allowed to pass in only one of the layers, the charge carriers in the secondlayeraredraggedduetothemomentumtransferpro- cess. Here the distance between the layers is large enough so that tunneling eects are not signicant. A drag voltage VD is measured under the condition that no current ows in this second layer. Thus, the transresistivity D =(w=l)VD=I (where w=l is a geometrical factor) probes the Coulomb interaction eects in double-layer electron systems in a transport experiment. The drag eect is being studied ex- perimentally in a variety of setups in which the charge carriers electrons, holes, or one of each [2–4]. The theoreti- cal eorts have concentrated on calculating the momentum transfer rate due to dierent mechanisms within many-body theory [1,5,6]. We consider two parallel quantum wells separated by a distance d. The bare Coulomb interaction between the elec- tronsisgivenby Vij (q)=(2e 2 =0)e -qd(1- ij ) Fij (q),inwhich ∗ Corresponding author. Tel.: +90-312-2901591; fax: +90-312- 2664529. E-mail address: tanatar@fen.bilkent.edu.tr (B. Tanatar). i and j label the layers, and 0 is the background dielectric constant. The intra and interlayer Coulomb interactions are modied by Fij (q) describing the nite extent of the quan- tum wells in the direction perpendicular to the layers [2]. The 2D electron density n is related to the Fermi wave vec- tor by n = k 2 F = 2. We use the dimensionless electron gas parameter rs = √ 2= (kFa ∗ B ), in which a ∗ B = 0= (e 2 m ∗ ) is the eective Bohr radius in the semiconducting layer with elec- tron eective mass m ∗ . The transresistivity measured in a Coulomb drag exper- iment for double-layer systems has been derived through a variety of theoretical approaches [1,5]. For simplicity and without loss of generality, we consider equal electron den- sities in both layers. In a microscopic approach, the drag resistivity is given by D = 1 8 2 e 2 n 2 T ∞ 0 dqq 3 × ∞ 0 d! W12(q; !)Im 0(q; !) sinh(!= 2T ) 2 ; (1) where we have assumed ˝ and kB =1.Here, 0(q; !)isthe 2D dynamic susceptibility, describing the density-density response function of a single layer electron system. W12(q; !) is the dynamically screened interlayer eec- tive interaction. We compare various approximations for 1386-9477/03/$-see front matter ? 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S1386-9477(02)01069-X