# Theoretical Condensed Matter Physics

Faculty: |
Robert Sekerka (Emeritus) Robert Swendsen Michael Widom Di Xiao |

## Group Overview

The field of Condensed Matter Physics includes the structure and dynamics of matter from the nanoscale to bulk matter. The objective is to understand the fundamental principles underlying thermal, electronic and mechanical properties of materials. Researchers at Carnegie Mellon currently employ theoretical methods of statistical mechanics, quantum mechanics and applied mathematics, e.g., partial differential equations, in order to simulate abstract or realistic model systems that relate to phase transitions, hydrodynamics, metals, semiconductors and biological materials.

## Member Research Thrusts

**Robert Sekerka** employs modeling on the mesoscopic scale (e.g., Phase Field methods or Lattice Boltzmann techniques) to investigate phenomena associated with fluid dynamics, surfaces and interfaces. Recent examples include dynamics of fluids in two-phase flows, the effect of entropy (due to colony structure) on crystal faceting, and the modeling of triple junctions where three phases meet along a line or curve. He also conducts research to develop quantitative models of high temperature deformation of metals in cooperation with colleagues from NIST, as well as computation of highly anisotropic growth of ice from the melt in the nearly-weightless enviroment of the International Space Station, in cooperation with Japanese colleagues.

**Robert Swendsen**'s research concerns condensed matter physics and statistical mechanics, with an emphasis on computer simulations. He develops new algorithms to investigate problems in computer simulations of phase transitions, renormalization group analysis, magnetism, crystal growth, and biological molecules.

**Mike Widom** combines quantum mechanics-based total energy calculations with principles of statistical mechanics to model the structure and thermodynamic stability of complex metallic structures. Specific materials of current interest include liquid and amorphous metals, and structures with local or global icosahedral symmetry.

**Di Xiao's** research interests lie in quantum condensed matter theory. One major direction of his research is to understand and predict material properties (transport, magnetic, and optical) from the viewpoint of Berry phase and topology. In particular, he is interested in topological phenomena arising from spin-orbit coupling and many-body interactions. These phenomena are often characterized by novel electromagnetic responses, which may be useful for applications in quantum electronics and quantum computing.