Search results for "Thermal transport"
showing 6 items of 6 documents
Electronic structure and transport properties of the Heusler compound Co2TiAl
2009
The properties of the Heusler compound Co2TiAl were investigated in detail by experimental techniques and theoretical methods. X-ray diffraction measurements indicate that as-cast samples of the compound exhibit the L21 structure with a small amount of B2-type disorder. This leads to a reduced saturation magnetization per formula unit of 0.747 μB. The Curie temperature is approximately 120 K. The transport properties are influenced by the change in the electronic structure at the Curie temperature, as revealed experimentally by conductivity, thermal transport and specific heat measurements. Different theoretical models based on ab initio calculations of the electronic structure are used to …
Electron-phonon heat transport in arrays of Al islands with submicrometer-sized tunnel junctions.
1996
We present experimental evidence of the effect of electrode volume and its shape on thermalization of small metallic islands for single electron tunneling. We have investigated the power law and the magnitude of the thermal transport and found that it obeys the common ${T}^{5}$ law for electron-phonon coupling only for the smallest islands studied, and in other cases considered, with cooling fins attached to the islands, the coupling per unit volume is weaker and it rather follows a law $\ensuremath{\propto}{T}^{p}$, where $pl5$. We attribute this to local hot electrons adjacent to the tunnel junctions.
Engineering thermal conductance using a two-dimensional phononic crystal
2014
Controlling thermal transport has become relevant in recent years. Traditionally, this control has been achieved by tuning the scattering of phonons by including various types of scattering centres in the material (nanoparticles, impurities, etc). Here we take another approach and demonstrate that one can also use coherent band structure effects to control phonon thermal conductance, with the help of periodically nanostructured phononic crystals. We perform the experiments at low temperatures below 1 K, which not only leads to negligible bulk phonon scattering, but also increases the wavelength of the dominant thermal phonons by more than two orders of magnitude compared to room temperature…
Thermal Transport and Wiedemann-Franz Law in the Disordered Fermi Liquid
2014
We study thermal transport in the disordered Fermi liquid at low temperatures. Gravitational potentials are used as sources for finding the heat density and its correlation function. For a comprehensive study, we extend the renormalization group (RG) analysis developed for electric transport by including the gravitational potentials into the RG scheme. Our analysis reveals that the Wiedemann-Franz law remains valid even in the presence of quantum corrections caused by the interplay of diffusion modes and the electron electron interaction. In the present scheme this fundamental relation is closely connected with a fixed point in the multi-parametric RG-flow of the gravitational potentials.
Phonon Cooling of Nanomechanical Beams with Tunnel Junctions
2009
We demonstrate electronic cooling of 1D phonon modes in suspended nanowires for the first time, using normal-metal-insulator-superconductor (N-I-S) tunnel junctions. Simultaneous cooling of both electrons and phonons to a common temperature was achieved. In comparison with nonsuspended devices, better cooling performance is achieved in the whole operating range of bath temperatures between 0.1-0.7 K. The observed low-temperature thermal transport characteristics are consistent with scattering of ballistic phonons at the nanowire-bulk contact as being the mechanism limiting thermal transport. At the lowest bath temperature of the experiment approximately 100 mK, both phonons and electrons in…