Electrical and thermal transport by nodal quasiparticles in thed-density-wave state

We compute the electrical and thermal conductivities and Hall conductivities of the d-density-wave (DDW) state in the low-temperature impurity-scattering-dominated regime for low dopings, at which they are dominated by nodal quasiparticles. We show that the longitudinal conductivity in this limit in the DDW state is not Drude like. However, the thermal conductivity is Drude like; this is a reflection of the discrepancy between electrical and thermal transport at finite frequency in the DDW state. An extreme example of this occurs in the μ=0, →τ∞ limit, where there is a strong violation of the Wiedemann-Franz law: κₓₓ/σₓₓ∝T² at ω=0 and κₓₓ/σₓₓ=0 at finite frequency. The DDW electrical and thermal Hall conductivities are linear in the magnetic field, B, for weak fields. The formation of Landau levels at the nodes leads to the quantization of these Hall conductivities at high fields. In all of these ways, the quasiparticles of the DDW state differ from those of the d_x²-y² superconducting state.