home > seminars 2016 > Chinedu Ekuma

Dr. Chinedu Ekuma
Department of Physics & Astronomy, Howard University

Wednesday September 21, 3:30 PM
Thirkield Hall (Physics), room 103


The role of Spatial and Electron Correlations in Electron Localization in Materials [PDF]

ABSTRACT: Correlated materials, especially in low-dimensions are promising for exploring the possibility of engineering new or improved materials for nanoelectronic applications. This promise stems from the fact that the properties of correlated materials emerge from rather complicated competition between the electron degrees of freedom that can be tuned to improve device performance. Often, materials are prone to defects and at the microscale, these inhomogeneities appear to be intrinsic. Besides, extrinsic doping can lead to a better understanding of the ground state properties of materials. To explore the role of defects in materials, the density functional theory using supercell approach or the single-site coherent potential approximation (CPA) and cluster extensions are the frequently used computational methods. While the CPA and cluster extensions deal explicitly with algebraically, average statistical disorder distributions, the DFT supercell approach can only describe ordered defect structures. Due to the intrinsic nature of the CPA, i.e., its self-consistency is based on arithmetically averaged density of states (DoS), it does not adequately account for rare events that induce electron localization, e.g., in disordered materials.  In this talk, I will discuss a first-principles, effective medium approach that appropriately characterizes disordered materials even in the proximity of electron localization transition. The first-principles typical medium dynamical cluster approximation (TMDCA@DFT) unlike the CPA, utilizes the typical density of states defined as the geometric average of the local DoS as the intrinsic order parameter for characterizing localization transitions.