Berlin 2012 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 4: Transport: Topological Insulators 1 (jointly with HL and MA)
TT 4.10: Talk
Monday, March 26, 2012, 12:00–12:15, H 3010
Tuning the Fermi velocity of Dirac cones: Towards an anomalous quantum Hall effect on the surfaces of topological insulators? — •Lars Fritz, Matthias Sitte, and Achim Rosch — Universität zu Köln, Institut für theoretische Physik, Zülpicher Strasse 77, 50937 Köln
Long-range Coulomb interaction can trigger an instability of two-dimensional Dirac fermions, the so-called chiral symmetry breaking. Three-dimensional topological insulators host two-dimensional helical Dirac fermions on their surfaces. We investigate whether long-range Coulomb interaction, controlled by the dimensionless coupling constant α = e2/(ℏ єr є0 vF), can induce surface ferromagnetism thereby gapping the surface metal. This is accompanied by an anomalous quantum Hall effect without explicit breaking of time-reversal invariance by an external magnetic field. We find that the prerequisite for observing this effect is to reduce the Fermi velocity vF of the surface Dirac fermions while keeping the bulk dielectric constant єr finite. We discuss under which conditions this can be achieved.