Dynamical susceptibility of a near-critical nonconserved order parameter and quadrupole Raman response in Fe-based superconductors

作者：Klein Avraham^*; Lederer Samuel; Chowdhury Debanjan; Berg Erez; Chubukov Andrey

来源：Physical Review B, 2018, 98(4): 041101.

DOI：10.1103/PhysRevB.98.041101

We analyze the dynamical response of a two-dimensional system of itinerant fermions coupled to a scalar boson Phi, which undergoes a continuous transition towards nematic order with a d-wave form factor. We consider two cases: (a) when Phi is a soft collective mode of fermions near a Pomeranchuk instability, and (b) when it is an independent critical degree of freedom, such as a composite spin order parameter. In both cases, the order parameter is not a conserved quantity and the d-wave fermionic polarization beta(q, Omega) remains finite even at q = 0. The polarization beta(0, Omega) has similar behavior in the two cases, but the relations between beta(0, Omega) and the bosonic susceptibility chi(0,Omega) are different, leading to different forms of chi"(0,Omega), as measured by Raman scattering. We compare our results with polarization-resolved Raman data for the Fe-based superconductors FeSe1_S-x(x), NaFe1_xCoxAs, and BaFe2As2.

• 出版日期2018-7-3
• 单位MIT