In-Plane Thermal Conductivity ofNd2CuO4: Evidence for Magnon Heat Transport (original) (raw)
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Magnetic heat transport in R_2CuO_4 with R = La, Pr, Nd, Sm, Eu, and Gd
2005
We have studied the thermal conductivity κ on single crystalline samples of the antiferromagnetic monolayer cuprates R2CuO4 with R = La, Pr, Nd, Sm, Eu, and Gd. For a heat current within the CuO2 planes, i. e. for κ ab we find high-temperature anomalies around 250 K in all samples. In contrast, the thermal conductivity κc perpendicular to the CuO2 planes, which we measured for R = La, Pr, and Gd, shows a conventional temperature dependence as expected for a purely phononic thermal conductivity. This qualitative anisotropy of κi and the anomalous temperature dependence of κ ab give evidence for a significant magnetic contribution κmag to the heat transport within the CuO2 planes. Our results suggest, that a large magnetic contribution to the heat current is a common feature of single-layer cuprates. In addition, we find that already weak charge carrier doping causes a strong suppression of κmag.
Heat transport in doped SrCuO2
Journal of Magnetism and Magnetic Materials, 2005
We report results on the heat transport in the spin chain system Sr 1Àx Ca x CuO 2 : The thermal conductivity in this compound is strongly anisotropic indicating excess thermal conductivity in the chain direction. Upon Ca-doping the thermal conductivity due to acoustic phonons is effectively suppressed, allowing a better qualitative and quantitative analysis of the excess thermal conductivity.
Scattering processes and magnon thermal conductivity in La5Ca9Cu24O41
Journal of Magnetism and Magnetic Materials, 2005
We analyse the temperature dependence of the 1D magnon heat transport in La 5 Ca 9 Cu 24 O 41 which contains undoped two-leg spinladders. In particular, we discuss possible scattering mechanisms which become relevant at elevated temperatures and thereby reduce the magnon thermal conductivity. Within the framework of a kinetic model, we find that the temperature dependence of the magnon mean free path l mag is well described if scattering of magnons by non-dispersive optical phonons is assumed. The phonon gap D % 800 K extracted from the analysis is in good quantitative agreement with the energy of the Cu-O bond stretching modes in the ladder planes.
First-Principles Study of UO 2 Lattice Thermal-Conductivity: A Simple Description
SSRN Electronic Journal, 2019
Modeling the high-T paramagnetic state of bulk UO2 by a non-spin-polarized calculation and neglecting the Hubbard-U correction for the f electrons in U atoms, the lattice thermal conductivity of bulk UO2 is investigated by the exact solution of the Boltzmann transport equation for the steadystate phonon distribution function. The results show that TA branches corresponding to U-atoms vibrations have the largest lifetimes and therefore have dominant role in thermal conductivity, while the optical branches corresponding mainly to O-atoms vibrations have the shortest lifetimes. Using this simple model, our results for the thermal conductivity show a very good agreement with the experiments. The calculations are repeated for bulk UO2 with different U-235 concentrations of 3%, 5%, 7%, and 20%, and the results show a small decrease of thermal conductivity which arise from scattering of phonons by impurities.
2002
The angle dependence at different temperatures of the longitudinal thermal conductivity kappaxx(theta)\kappa_{xx}(\theta)kappaxx(theta) in the presence of a planar magnetic field is presented. In order to study the influence of the gap symmetry on the thermal transport angular scans were measured up to a few Kelvin below the critical temperature TcT_cTc. We found that the four-fold oscillation of kappaxx(theta)\kappa_{xx}(\theta)kappaxx(theta) vanishes at T>20T > 20 T>20K and transforms into a one-fold oscillation with maximum conductivity for a field of 8 T applied parallel to the heat current. Nevertheless, the results indicate that the d-wave pairing symmetry is the main pairing symmetry of the order parameter up to TcT_cTc. Numerical results of the thermal conductivity using an Andreev reflection model for the scattering of quasiparticles by supercurrents under the assumption of d-wave symmetry provide a semiquantitative description of the overall results.
Spinon thermal conductivity of-(CuO2)-spin chains in LiCuVO4
Physics of the Solid State, 2004
The thermal conductivity of the quasi-one-dimensional (S = 1/2) Heisenberg antiferromagnet LiCuVO 4 with uniform (-CuO 6-) spin chains aligned parallel to the b axis in a crystal with an orthorhombically distorted inverse spinel structure is measured in the temperature range 10-300 K. The spinon component of the thermal conductivity is separated out.