The dynamical fluorescent microthermal imaging (FMI) experiment has been used to investigate the phonon-magnon interaction in the 1D Heisenberg antiferromagnet La5Ca9Cu24O41. This material shows highly anisotropic heat conductivity due to the efficie
nt magnetic heat transport along the spin ladders in the compound. To extract information on the phonon-magnon interaction we modelled the dynamic heat transport experiment using a two temperature model approach, taking both the crystal as well as the PMMA/EuTTA fluorescent heat imaging layer into account. The simulations are carried out by the finite element method using COMSOL Multiphysics Heat Transfer Module. The results of the numerical calculations are expected to be used for the data analysis of the experimental studies.
We report a comparative Raman spectroscopic study of the quasi-one-dimensional charge-density-wave systems ab (A = K, Rb). The temperature and polarization dependent experiments reveal charge-coupled vibrational Raman features. The strongly temperatu
re-dependent collective amplitudon mode in both materials differ by about 3 cm, thus revealing the role of alkali atom. We discus the observed vibrational features in terms of charge-density-wave ground state accompanied by change in the crystal symmetry. A frequency-kink in some modes seen in bb between T = 80 K and 100 K supports the first-order lock-in transition, unlike rb. The unusually sharp Raman lines(limited by the instrumental response) at very low temperatures and their temperature evolution suggests that the decay of the low energy phonons is strongly influenced by the presence of the temperature dependent charge density wave gap.
