Fig. 2: Observation of TA Kohn anomaly.
From: Incommensurate Transverse Peierls Transition and Signature of Chiral Charge Density Wave in EuAl4
a, b show TA phonon dynamical structure factor, S(Q, ω) along the (2, 2, L\(\in\) [1.5, 2.0]) direction, at T = 300 and 160 K, respectively. Red and cyan diamonds are extracted phonon peak positions at 300 and 160 K, respectively. The dashed curves represent the sinusoidal bare band of the TA phonon. Right panels in (a, b) show magnified view of S(Q, ω) near QCDW (dashed rectangles in the left panels). c, d are the same plots (including color scales) as (a, b) but along the (0, 0, L\(\in\) [7.5, 8.0]) direction to select the LA phonon branch. e Temperature dependence of extracted TA and LA phonon dispersions. The TA phonon modes show a large energy renormalization whereas the LA phonons are slightly hardened. Horizontal and vertical dashed lines in (a−e) corresponding to elastic line and QCDW, respectively. f Temperature dependent IXS spectra at Q = (2,2,1.83). The vertical dashed line represents the elastic line. g TA phonon softening, \(\Delta E(T)\) at 300 K, 160 K and 130 K, relative to the bare band dispersion (dashed sinusoidal curves (a)). The vertical dashed line represents the QCDW. The error bars shown in (a–e) represent 1-standard deviation from least-squares fitting. The error bars shown in (f) represent 1-standard deviation from Poissonian statistics.
