Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 55: Low-Dimensional Systems: 2D – Theory

TT 55.6: Talk

Wednesday, March 18, 2015, 10:45–11:00, H 3010

Two--parameter scaling theory of transport near a spectral node — •Andreas Sinner — Universität Augsburg

We investigate the finite--size scaling behavior of the conductivity in a two--dimensional Dirac electron gas within a chiral sigma model. Based on the fact that the conductivity is a function of system size times scattering rate, we obtain a two--parameter scaling flow toward a finite fixed point. The latter is the minimal conductivity of the infinite system. Depending on boundary conditions, we also observe unstable fixed points with conductivities much larger than the experimentally observed values, which may account for results found in some numerical simulations. By including a spectral gap we extend our scaling approach to describe a metal--insulator transition.