Smectons: Soft modes in electronic stripe phases, and their consequences for thermodynamics and transport

The Goldstone mode due to stripe or unidirectional charge-density-wave order in electron systems is found to have the same functional form as the one in classical smectic liquid crystals. It is very similar to the Goldstone mode that results from helical magnetic order. This allows for an effective theory that provides a quasiparticle description of either stripe phases or helimagnets in the low-energy regime. The most remarkable observable consequence is an electronic relaxation rate in d=2 that is 1/\tau ~ T\ln T in clean systems and 1/\tau ~ \sqrt{T} in weakly disordered ones. The corresponding results in d=3 are 1/\tau ~ T^{3/2} and 1/\tau ~ T, respectively.