The studies in this thesis are focused on the physical effects in the flat band materials. The results contain the discovery of strong enhancement of RKKY spin-spin interactions with specific... Show moreThe studies in this thesis are focused on the physical effects in the flat band materials. The results contain the discovery of strong enhancement of RKKY spin-spin interactions with specific geometric arrangement and dynamical generation of excitonic order parameter with high magnitude. A number of physical properties influenced by flat band are studied: optical conductivity, orbital susceptibility and spectral functions in the case of flat-band lattices stacked into bilayer. Additional chapters contain the studies of the methods to distinguish Majorana zero modes from Andreev levels and Majorana fermions in superconductors. Show less
Charge counting statistics (C.S.) of traversing electron in quantum devices like atomic-molecular junctions is sensitive to the local perturbation in the charge field at the contact and in the... Show moreCharge counting statistics (C.S.) of traversing electron in quantum devices like atomic-molecular junctions is sensitive to the local perturbation in the charge field at the contact and in the quantum channels. The first cumulant of C.S. i.e. current-voltage characteristic of such devices has been tool for such investigation since long time. Here we have used the second cumulant i.e. shot noise to study the electron-electron and electron-phonon interaction in the atomic contacts. The shot noise measurement on the Au atomic chain reveals the inelastic scattering in the noise. These signatures can provide vital information on the feedback of the local phonon population on electron transport. The current-voltage characteristic of the ferromagnetic atomic contacts unexpectedly shows zero bias anomalies. This observation is attributed to the interaction of traversing electron with localized magnetic moments within same host species. The observed connection between the Fano factor and the weight of the zero bias anomalies supports the view that the zero bias anomaly originates from spin scattering by localized magnetic moments. However, whether this is true Kondo scattering as suggested by Calvo et al. cannot be stated conclusively from our data. At the end of thesis we have presented a low noise high frequency broadband noise measurement setup suitable for break junction setup. Show less
This thesis addresses a variety of systems in which the diffusion is anomalous, mainly motivated by recent experimental developments. The main topics discussed are: * We look at the consequences... Show moreThis thesis addresses a variety of systems in which the diffusion is anomalous, mainly motivated by recent experimental developments. The main topics discussed are: * We look at the consequences that subdiffusion on fractals has for shot noise. * The effects correlations have on superdiffusion in one dimension are examined. * We develop and demonstrate the usefulness of a method to simulate the anomalous diffusion of Dirac fermions in a computer. * A spin precession experiment in topological insulators is proposed and analyzed. * We present the mechanism for the conversion of an ordinary insulator into a topological insulator by disorder which was reported in the literature, on the basis of computer simulations, but had remained unexplained. Show less
In society there is a constant urge to improve existing devices and the level of success is perhaps the easiest to observe in the world of electronic devices. The complexity, functionality and... Show moreIn society there is a constant urge to improve existing devices and the level of success is perhaps the easiest to observe in the world of electronic devices. The complexity, functionality and reliability of these machines has increased enormously, but it approaches its limits. A new giant step which will provide the space for further development is the concept of molecular electronics where organic molecules and their natural characteristics are used as the functional units. The research presented in this thesis is a small part of the large effort which the scientific community puts nowadays into this goal. The system under the investigation is molecular bridge where the molecule is hydrogen or CO or acetylene or benzene. We characterise junctions by point contact spectroscopy and can address different modes of oscillation by following stretching dependence of vibration energy. Show less
