Simulations of Competing Phases and Quantum Criticality in Strongly Correlated Materials

Louisiana State University, Baton Rouge LA

Investigators

Abstract

NONTECHNICAL SUMMARY The Division of Materials Research funds this award that supports research and education on the development of new formalisms, algorithms and codes, and on their use in the study of complex behavior of constituent electrons in materials. One of the most fascinating areas of materials science is the study of how electrons organize in materials, giving rise to different quantum phases, such as metals, insulators, semiconductors or superconductors, which are characterized by different and technologically important properties. Quantum criticality occurs when multiple such phases coexist and compete in a material. At the boundaries between these phases, it is possible that no well-established phase exists; as a result, completely new states of matter may emerge. These new phases and their competition is not only fascinating from a fundamental standpoint, but may also hold the promise of new applications and functionalities since at a tenuous balance between phases, the application of an electric or magnetic field, or pressure, or changes in the chemical composition of the material may dramatically change its properties. New functionalities may then emerge as the system "switches" between the different states. The project entails developing relevant methodology, and will use supercomputers to study these quantum critical states of matter, the competition between different phases, and their response to different external fields. The research will be carried out in collaboration with researchers in India, furthering an established international collaboration involving several present and former students. The project will also involve a number of outreach efforts developed to increase student interest and achievement in the sciences, and to encourage students to consider STEM careers. The researchers funded by the award will participate in a Beowulf Bootcamp each summer where high-school students will construct and use a small supercomputer. TECHNICAL SUMMARY The Division of Materials Research funds this award that supports research and education on complex behaviors in correlated electronic materials, including competing phases in cuprate superconductors, heavy-Fermion systems, and disordered interacting electronic systems and superconductors. Special emphasis will be placed on identifying and studying new quantum critical points and competing phases, and the Anderson disorder-driven quantum phase transition and its competition with interactions. The goal of this project is to continue the development of new formalisms, algorithms and codes, and to use them in the study complex behavior in correlated electronic materials. The research team will focus on simulations of quantum criticality and disordered interacting models near localization. Quantum criticality is of great fundamental interest, since the associated transitions are driven by quantum rather than thermal fluctuations. The PI and his group will develop a better understanding of the competing phases in correlated and strongly disordered systems that could lead to new functionalities, including the Anderson metal-insulator transition, and other quantum phase transitions. A more complete understanding of quantum criticality may in turn lead to a better understanding of high-temperature superconductors and other technologically important materials. The project will employ an array of theoretical/computational tools including multiscale approaches, quantum Monte Carlo, and fast approximate cluster solvers, and novel methods to treat disordered interacting systems near an Anderson localization transition including the recently developed typical-medium dynamical cluster approximation used to study the Anderson localization quantum phase transition. The research will be carried out in collaboration with researchers in India, furthering an established international collaboration involving several present and former students. The project will also involve a number of outreach efforts developed to increase student interest and achievement in the sciences, and to encourage students to consider STEM careers. The researchers funded by the award will participate in a Beowulf Bootcamp each summer where high-school students will construct and use a small supercomputer.