Calorimetric study of superconducting indium in porous Vycor glass

In this thesis work I have made the first extensive thermodynamic study on Indium nanoparticles formed in 5.6 nm pore size porous Vycor glass (PVG). The experiments were carried out by using both AC calorimetry and thermal relaxation in a temperature range from 1.2 K to 10 K and under different applied magnetic fields. The dramatic change of physical properties of the indium nanoparticle were clearly observed.;First, Indium in Vycor has changed from conventional Type-I superconductor to type-II superconductor. The observed magnetic flux jumps provide remarkable direct evidence of the mixed state in this composite. Second, a dramatic enhancement of lattice specific heat was observed and interpreted as consequence of the enhanced effect of low frequency surface phonon modes effect due to the large surface-to-volume ratio of the small particle system. Third, the discrete nature of the phonon spectrum due to the size effect of the system is revealed by the fact that the enhancements of specific heat start to fall off at lower temperature. Fourth, a strong intergranular coupling was inferred from the lack of the broadening in the discontinuity of specific heat in the transition region, and from the relatively large estimated value of the electron transmission coefficient for the tunneling junction between indium grains in Vycor. Finally, in this thesis work I have developed a new method of studying microstructure of indium in Vycor: The frequency dependence of the thermal response is strongly dependent on the structure of the indium in PVG and the heat transfer processes between Vycor glass host and indium nanoparticles.;This thesis work has prepared basic experimental and analytical tools for general studies of the properties of indium in Vycor and other similar systems. Further experimental work on a variety of systems with different pore sizes pore structures and sample thickness is required to establish the universal and specific views on thermodynamic behavior in small particle systems.