2014 Theses Doctoral

A Correlated 1-D Monatomic Condensed Matter System: Experiment and Theory

Zaki, Nader Wasfy

A one-dimensional quantum mechanical system is experimentally synthesized and investigated for physical phenomena that it may inherit due to quantum confinement and electron correlations. The experimentally realized system is a self-assembled array of monatomic cobalt wires that are grown under ultra-high vacuum conditions on a vicinal copper (111) substrate using a recipe developed specifically for this work. This work experimentally demonstrates that this 1-D system undergoes a charge density wave instability, which is a first for such a 1-D phenomenon on a metallic substrate. It is determined experimentally that this 1-D system undergoes an electronic phase transition at a temperature of about 85K, in which the higher temperature electronic phase is itinerant rather than localized. Using ab initio density functional theory, the cause of the measured charge density wave instability is assigned to erromagnetic interactions along the chain. Specifically, it is deduced that the instability is driven by spin -minority pin-exchange interactions predominately in the cobalt dxz/dyz orbitals. Beyond, shedding light on electron correlations in a physically realized quantum mechanical 1-D system, this work demonstrates that this particular system is a new test-case example for advanced theoretical techniques in predicting the correct structural ground phase.