Emergent phenomena in spatially and energetically inhomogeneous strongly correlated model electron systems

Abstract

materials, (e.g. La1−xCaxMnO3), heavy fermion materials, (e.g. CeAl3, UPt3) or organic charge transfer salts, (e.g.). SCES serve to be an interesting paradigm in condensed matter physics from both fundamental and technological aspects [1–3]. The interplay of charge, orbital and lattice degrees of freedom in these materials give rise to a plethora of interesting phenomena, like, high temperature superconductivity/superconductors (HTSCs), colossal thermodynamic responses etc.. Conventional bandstructure theory fails to predict the physical properties of SCES, for example, the case of Mott insulators [4–6]. These are purely interaction driven insulators which otherwise in a tight-binding (band theoretical) model would be deemed as a metal. One of the recent trends in condensed matter physics is the study of strongly correlated heterostructures [2, 7]. Heterostructure geometries provide a fertile playground for tuning material properties. Especially, when the constituent materials are strongly correlated, they provide an even wider scope for realizing unconventional physics at hetero-interfaces. Recent experiments on such systems provide several novel scenarios opening possible directions for realizing tunable HTSCs [8] or SCES based ultrafast electronics [3], namely, Mottronics [9] or probing fundamental physics in heavy fermions [10, 11]. These systems are, however, spatially inhomogeneous owing to the hetero-structure geometry, or at most, quasi-periodic, as in superlattices. Moreover, the occurrence of a disordered interface is inevitable. While one of the works presented in this thesis deals with a novel prediction of an emergent quantum phase transition at such a hetero-interface, another work revolves around the implementation of a self-consistent theoretical framework that may be used to understand some aspects of such a disordered interface.