2012/06/28 by R. V. Gorbachev, Roman Gorbachev, A. K. Geim +14 · 10 citations
Materials Science · Physics and Astronomy · #Bilayer graphene #Condensed matter physics #Coulomb #Drag #Electric field #Electron #Graphene #Graphene research and applications #Mechanics #Physics #Quantum Electrodynamics and Casimir Effect #Quantum and electron transport phenomena #Quantum mechanics #cond-mat.mes-hall #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1038/nphys2441
published as Nature Phys 8, 896-901 (2012)
arxiv created 2012/06/28 · openalex publication_date 2012/10/12 · arxiv updated 2012/12/05 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Spatially separated electron systems remain strongly coupled by electron-electron interactions even when they cannot exchange particles, provided that the layer separation d is comparable to a characteristic distance l between charge carriers within layers. One of the consequences of this remote coupling is a phenomenon called Coulomb drag, in which an electric current passed through one of the layers causes frictional charge flow in the other layer. Previously, only the regime of weak (d>>l) to intermediate (d ~ l) coupling could be studied experimentally. Here we use graphene-BN heterostructures with d down to 1 nm to probe interlayer interactions and Coulomb drag in the limit d<<l where the two Dirac liquids effectively nest within the same plane, but still can be tuned and measured independently. The strongly interacting regime reveals many unpredicted features that are qualitatively different from those observed previously. In particular, although drag vanishes because of electron-hole symmetry when either layer is neutral, we find that drag is at its strongest when /both/ layers are neutral. Under this circumstance, drag is positive in zero magnetic field but changes its sign and rapidly grows in strength with field. The drag remains strong at room temperature. The broken electron-hole symmetry is attributed to mutual polarization of closely-spaced interacting layers. The two-fluid Dirac system offers a large parameter space for further investigation of strong interlayer interaction phenomena.