Disorder and the emergence of inhomogeneous phases in strongly correlated electron systems

University Of Florida, Gainesville FL

Investigators

Abstract

TECHNICAL SUMMARY This award supports theoretical and computational research and educational activities related to the problem of inhomogeneous competing order in metals. An increasing number of novel materials exhibit emergent inhomogeneous phases, which are states of matter where the ground state is modulated and may display various types of long-range order. The theory of such states, which represents a fundamental departure from the basic momentum-space one-particle paradigms of condensed matter physics, is still in its infancy. Along this direction, the PI will study the general question of how inhomogeneous order emerges and how the particular choice taken by the system depends on disorder, interactions, and its electronic structure. Models will be studied which are applicable to a diverse class of interacting systems, appropriate for heavy fermion, iron-pnictide, cuprate, and other oxide materials. An improved understanding of the role of disorder in the presence of competing ordered states will facilitate the identification of the most important instabilities in various systems, and enable researchers to focus on the intrinsic aspects of exotic ordering phenomena such as high temperature superconductivity. This award supports research, which is ultimately expected to have an impact on the design and development of oxide materials for applications. It is noteworthy that the entire electronics industry is built on doped semiconductor devices at present, and may be said to have been so successful in part because solutions were found to prevent electron mobilities from being limited by disorder which accompanies the doping process. Since in correlated systems and novel oxides in particular, impurities have a much more important impact, specifically through their nucleation of inhomogeneous phases, these problems represent important and also practical hurdles to be surmounted before oxide electronics can succeed in the marketplace. The PI will train two graduate students during the course of the project. The PI will also engage in outreach activities to educate school children in the Gainesville area about superconductivity and notions of order and disorder which are important in many disciplines of science. NONTECHNICAL SUMMARY This award supports theoretical and computational research and educational activities related to the problem of "inhomogeneous competing order" in metals. This fascinating situation occurs when a complex material is close to making a transition from one electronic phase to another, and two or more different quantum mechanical states become so close in energy as to be essentially indistinguishable. Rather than deciding to form in one or the other of these states, in the presence of small amounts of impurities or imperfections, the material sometimes forms an inhomogeneous state, which varies in composition from point to point in space. Materials that exhibit such exotic behavior can be potentially tuned for use in so-called smart materials which can improve the way many different electronic devices work. In this project, the PI will perform theoretical calculations and computer simulations on a variety of novel materials where disorder is known to play a role of this type, to understand how superconductivity, an electronic state that can conduct electricity without resistance, and magnetism can be influenced by impurities. This is fundamental research aimed to advance our understanding of materials that are very sensitive to impurities and imperfections leading to unusual quantum mechanical states of electrons. Many of these states appear to be connected to superconductivity. This research contributes to understanding key properties of materials that lead to superconductivity. The PI will train two graduate students during the course of the project. The P.I. will also engage in outreach activities to educate schoolchildren in the Gainesville area about superconductivity and notions of order and disorder which are important in many disciplines of science.