Fig. 4: Model calculation.
a Calculation of the EgRaman response using a simple model of two degenerate harmonic oscillators coupled via λ to a fluctuating nematic degree of freedom. Details of the calculation are laid out in the Supplementary Note 4. Parameters for the B1g fluctuation frequency and temperature are chosen Ω = ω0/20, T = ω0/5. b The weight distribution of the peak splitting depends on the relative energy scales in the problem, as illustrated for two different temperatures T ≪ Ω and Ω ≪ T ≪ ω0. c In the disordered case with equal peak splitting the degeneracy of the two Raman responses can be lifted by applying a conjugate external strain σext. d Schematic of the allowed transitions that cause the peak splitting of the Raman signal even in the tetragonal state (left panel) and in the strained/orthorhombic state (right panel). e Raman response of BaNi2As2stress-free and under uniaxial stress and comparison to local stress dependence (f) of FeSe [Data from ref. 12, plotted with permission from the authors].
