Stable non-Fermi liquid fixed point at the onset of incommensurate $2k_F$ charge density wave order

Abstract

We consider the emergence of a non-Fermi liquid fixed point in a two-dimensional metal, at the onset of a quantum phase transition from a Fermi liquid state to an incommensurate charge density wave (CDW) ordered phase. The momentum of the CDW boson is centred at the wavevector $ \boldsymbol{ \mathcal Q} $, which connects a single pair of antipodal points on the Fermi surface with antiparallel tangent vectors. We employ the dimensional regularization technique in which the co-dimension of the Fermi surface is extended to a generic value, while keeping the dimension of the Fermi surface itself fixed at one. Although the system is strongly coupled at dimension $d=2$, the interactions become marginal at the upper critical dimension $d=d_c$, whose value is found to be $ 5/2$. Using a controlled perturbative expansion in the parameter $\epsilon = d_c - d $, we compute the critical exponents of the stable infrared fixed point characterizing the quantum critical point. The scalings of the original theory are determined by setting $\epsilon =1/2$, where the fermion self-energy is seen to scale with the frequency with a fractional power law of $2/3$, which is the telltale signature of a typical non-Fermi liquid phase.