Two regimes in conductivity and the Hall coefficient of underdoped cuprates in strong magnetic fields

We address recent experiments shedding light on the energy spectrum of under- and optimally doped cuprates at temperatures above superconducting transition. Angle resolved photoemission reveals coherent excitation only near nodal points on parts of the "bare" Fermi surface known as the Fermi arcs. The question debated in the literature is whether the small normal pocket, seen via quantum oscillations exists at higher temperatures or forms below a charge order transition in strong magnetic fields. Assuming the former case as possibility, expressions derived for the resistivity and the Hall coefficient (in weak and strong magnetic fields) with both types of carriers participating in transport. There are two regimes. At higher temperatures (at a fixed field) electrons are dragged by the Fermi arcs' holes. The pocket being small its contribution into conductivity and the Hall coefficient is negligible. At lower temperatures electrons decouple from holes behaving as a Fermi gas in the magnetic field. Mobility of holes on the arcs decreasing in strong fields with decrease of temperature, below a crossover point the pocket electrons prevail changing sign of the Hall coefficient in the low temperature limit. Such behavior finds its confirmation in recent high-field experiments.