Probing the Topological Exciton Condensate via Coulomb Drag

Abstract

The onset of exciton condensation in a topological insulator thin film was recently predicted. We calculate the critical temperature for this transition, taking into account screening effects. Furthermore, we show that the proximity to this transition can be probed by measuring the Coulomb drag resistivity between the surfaces of the thin film as a function of temperature. This resistivity shows an upturn upon approaching the exciton-condensed state.

Anomalous low-temperature Coulomb drag in graphene-GaAs heterostructures

“…Similar results were obtained on the basis of a Kubo-formula approach 57 . Within these frameworks, the enhancement is attributed to e-h pairing fluctuations extending above T c for a phase transition into an exciton condensed phase 1,17,18,57,58 . If this scenario is correct, Fig.…”

“…In addition to the fundamental interest in understanding when these phenomena occur in nature, there is a practical interest in discovering many-particle systems where these types of orders occur under less extreme physical conditions, in particular in the absence of strong magnetic fields and, possibly, at non-cryogenic temperatures. Interest in interlayer excitons has been recently revitalized [10][11][12] by theoretical predictions of high-temperature spontaneous coherence and superfluidity in electrically decoupled graphene layers [13][14][15] and topological insulator thin films [16][17][18][19] . The former systems are just examples of van der Waals heterostructures 20 in which different layered materials are combined to offer novel opportunities for applications [21][22][23] and fundamental studies [10][11][12] .…”

Coulomb drag

“…A microscopic theory of Coulomb drag in proximity to a phase transition was suggested by Hu (2000b) and Mink et al (2012Mink et al ( , 2013. As the system approaches the transition temperature T c from above, the drag resistivity was found to exhibit a logarithmic divergence…”

“…Several contradicting values of the transition temperature in double-layer graphene systems have been reported. The initial estimate (Mink et al, 2012;Zhang and Joglekar, 2008) of T c close to room temperature appeared to be too optimistic. Screening effects Efetov, 2008, 2010) were shown to lead to extremely low values under 1mk (T c ∼ 10 −7 E F ).…”

“…Drag or similar measurements of interlayer interactions were also considered for composite (or hybrid) systems comprising ballistic quantum wires Muradov, 2000, 2005;Raichev and Vasilopoulos, 2000a;Wang et al, 2005), coupled 2D-1D systems (Lyo, 2003), nonequilibrium charged gases (Wang and da Cunha Lima, 2001), multi-wall nanotubes (Lunde et al, 2005;Lunde and Jauho, 2004), quantum point contacts (Levchenko and Kamenev, 2008a), few level quantum dots (Moldoveanu and Tanatar, 2009), optical cavities (Berman et al, 2010a(Berman et al, , 2014, coupled mesoscopic rings (Yang and MacDonald, 2001), superconductors (Levchenko and Norman, 2011), and normalmetal-ferromagnet-normal-metal structures . Other developments include mesoscopic fluctuations of Coulomb drag (Narozhny and Aleiner, 2000;Narozhny et al, 2001), frictional drag mediated by virtual photons (Donarini et al, 2003) and plasmons (Badalyan et al, 2007), exciton effects in semiconductors (Laikhtman and Solomon, 2006) and topological insulators (Mink et al, 2012), interlayer Seebeck effect (Lung and Marinescu, 2011) and spin drag (Badalyan and Vignale, 2009;D'Amico and Vignale, 2000;Duine et al, 2011Duine et al, , 2010Duine and Stoof, 2009;Flensberg et al, 2001;Glazov et al, 2011;Pustilnik et al, 2006;Tse and Das Sarma, 2007;Vignale, 2005). Recently, the focus of the theoretical work was shifted towards the drag effect in graphene-based devices (Narozhny, 2007;Narozhny et al, 2015;Song et al, 2013; and strongly interacting high-mobility double...…”