Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Final Activity Report Summary - ELECTRONCOMPLEXITY (Emergent complexity in electronically frustrated correlated electron systems)

One of the most intriguing problems in nature is the change of a system from one phase to another. In condensed matter physics for example, this entails changes from an insulator into a metal or a superconductor, the widest range of change in matter. Notably, many interesting and technologically important materials ranging from field-effect transistors and magneto-restrictive films to superconductors find themselves close to a transition. In this regime, competition between several distinct ground states causes electronic heterogeneity, giving rise to coexistence of different ordered phases separated by one or more critical points. The associated electronic complexity has potential consequences for applications of materials.

Here, the behaviour of electrons is strongly correlated to the local environment of the system, because in addition to spin and charge the lattice and orbital degrees of freedoms are active, leading to large responses to small perturbations - a prerequisite for energy friendly, versatile technology. We studied the physics of strongly interacting many-body systems with regard to the occurrence and properties of complex macroscopic states. In the course of this research Programme, we demonstrated the implications of electronic heterogeneity in low dimensional systems with rich phase diagrams including insulating, metallic and superconducting ground states.

We introduced a further tuning parameter in our studies, dimensionality, which allowed us for the first time to utilise some of the abovementioned properties to control magnetism at the atomic scale. We also investigated methods to discover putative critical points and novel ground states on the border of magnetism, and the correlation with the physics of short-range phase coherence. Electronically frustrated correlated electron systems can be then tuned to be exactly at or on the cusp of the transition, where electrons behave most collectively, where with tuning of relevant parameters we alter matter to extreme cases.

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