The question is about collective modes of charge density waves, i.e., amplitude and phase fluctuations δ,ϕ of the order parameter Δ(x,t)=(Δ0+δ)eiϕ.
I read on p.1 of this paper that amplitude mode and phason mode can be expressed using the phonon normal coordinate Qq±2kF respectively as (2kF is the density wave vector) 1√2(Qq+2kF±Qq−2kF).
I also found in another review paper (p. 1135, eq(3.1)) the following. To the lowest order in the fluctuations δ,ϕ, the amplitude mode corresponds to Δ2kF+Δ−2kF=2Δ0+2δ and the phason mode corresponds to Δ2kF−Δ−2kF=2Δ0Δϕ. But I don't find a clear definition of Δ2kF in the paper. Still it's not clear how this is obtained.
No comments:
Post a Comment