Dynamical symmetry breaking in a 2D electron gas with a spectral node
arXiv:1207.3701 · doi:10.1140/epjb/e2013-40482-7
Abstract
We study a disordered 2D electron gas with a spectral node in a vicinity of the node. After identifying the fundamental dynamical symmetries of this system, the spontaneous breaking of the latter by a Grassmann field is studied within a nonlinear sigma model approach. This allows us to reduce the average two-particle Green's function to a diffusion propagator with a random diffusion coefficient. The latter has non-degenerate saddle points and is treated by the conventional self-consistent Born approximation. This leads to a renormalized chemical potential and a renormalized diffusion coefficient, where the DC conductivity increases linearly with the density of quasiparticles. Applied to the special case of Dirac fermions, our approach provides a comprehensive description of the minimal conductivity at the Dirac node as well as for the V-shape conductivity inside the bands.
13 pages, 4 figures, extended version
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- Quantum transport with strong scattering: Beyond the nonlinear sigma model
- Linear response peculiarity of a two--dimensional Dirac electron gas at weak scattering
- Weak-localization approach to a 2D electron gas with a spectral node
- Localization by particle-hole symmetry breaking: a loop expansion