جستجوی مقالات مرتبط با کلیدواژه « هدایت گرمایی » در نشریات گروه « فیزیک »

In this study, using density functional theory and Boltzmann equation, the thermoelectric properties of perfect and porous phosphorene nanosheets are calculated and compared at different temperatures including 100, 200 and 300 K. The results show that the maximum seebeck coefficient at 300 ° K for porous nanosheet is about twice the corresponding amount of the perfect one. A good thermoelectric material should have a high electrical conductivity as well as a low thermal conductivity. Although the electrical conductivity of the perfect sample is higher than that of the porous one at all studied temperatures, the electronic contribution of the thermal conductivity related to porous phosphorene is less than the thermal conductivity of the perfect one. At all studied temperatures, the maximum figure of merit (ZT) in porous phoephorene, is higher than the ZT in the perfect nanosheet. The results of this study indicate that two-dimensional porous phosphorene is a promising material for thermoelectric applications and even demonstrates a better performance than the perfect 2D-phosphoren.

The optical properties and thermal conductivity of carbon nanotubes in the presence of Nitrogen doping and electric field investigated via the Green's function method and tight binding approximation. The doping and external fields lead to modifications in the density of state (DOS), optical properties, electrical and thermal conductivity. The band gap decreases by the electric field until reaches zero and nanotubes with larger radius are more sensitive than small ones. The number and energies of peaks in the in the DOS and optical spectra are dependent on the electric field strength and doping concentration. The electrical and thermal conductivity increases with temperature until reaches maximum value then decreases. The behaviors of these parameters in the external electric field are different for pure and doped systems. By increasing the doping concentration and electric field strength, they decreases in higher temperature.

To understand the mechanism of superconductivity in unconventional super onductors is one of the big challenges in the field of superconductivity. Based on the BCS theory, there is a direct relation between the pairing mechanism and the symmetry of the order parameter. Therefore, identification of the structure of the superconducting gap or the order parameter provides key information on the pairing mechanism. The s-wave conventional superconductors have full point symmetry of the crystal lattice, thus they have full gap symmetry around the Fermi surface. This leads to the exponential temperature dependence of many physical properties in the superconducting state at low temperature. However, the presence of nodes imposed by symmetry in the gap function of unconventional superconductors implies a different order parameter other than conventional s-wave, which may lead to a different pairing mechanism. Here, we show how thermal conductivity measurements in CeIrIn5 at very low temperatures detect the superconducting gap structure.