Research in the Reichman Group

(A) Structure, Dynamics, Rheology and Self-Assembly of Soft Materials

For several years a major thrust of research in the Reichman group has been the theoretical description of the behavior and assembly of "soft" materials (colloidal suspensions, gels, membranes, polymer networks, etc). Our efforts in this broad area have spanned a range from analytical work (e.g. our work on sheared colloidal suspensions1,2), to coarse grained modeling (e.g. our work on non-equilibrium self-assembly of networks of nanoparticles3), to atomistic molecular dynamics and Monte Carlo simulations (e.g. our work on the interplay between microphase separation and gelation in charged attractive colloidal systems4). In this area we often collaborate with experimental groups such as the Weitz Group (Harvard)5,6,7, the Brus Group (Columbia)3 and the Whitesides Group (Harvard)8.

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Soft 1 Soft 2 Soft 3
(B) Statistical Mechanics of Disordered and Glassy Systems

Understanding the transition from a liquid to a glass has been called "the deepest and most interesting unsolved problem in solid state theory9." Our group investigates the behavior of supercooled liquids and glasses using both analytical and computational tools. The Reichman group has made major contributions to understanding the role of activated transport and the onset of glassy dynamics in supercooled liquids10,11, the description of non-linear susceptibilities related to dynamical heterogeneity12 and the connection between structure and dynamics in supercooled liquids13. Currently a major effort in the group is aimed at distinguishing purely kinetic scenarios of the glass transition from those driven by non-trivial changes in the entropy of available configurations14.

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Glass 1 Glass 2 Glass 3
(C) Out-of-Equilibrium Dynamics and Transport in Quantum Systems

Our group studies a wide variety of problems that involve the quantum behavior of correlated electronic systems that are driven out of equilibrium via contact to reservoirs held at different chemical potentials or temperatures or via a sudden change of interaction parameters (a "quantum quench")15. Our group uses analytical tools (e.g. bosonization) and has developed new numerical tools (e.g. iterative path-integral based schemes) to investigate these problems.

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Trans 1 Trans 2 Trans 3
(D) Quantum Liquids and Glasses

We have developed a microscopic theory to understand the dynamics of quantum fluids such as liquid para-Hydrogen16. Our theory is in good agreement with transport and scattering experiments in these systems17,18. Motivated by recent experimental and computational work suggesting novel features that arise from an interplay between intrinsically quantum mechanical fluctuations and glass formation19,20, we are currently using our approach to predict how quantum fluctuations modify classical scenarios of the glass transition. In a slightly different context we are investigating under what conditions interactions can lead to equilibration of an otherwise non-ergodic assembly of particles or spins21. A prime example of this type of quantum glass phenomena is the putative many-body localization transition whereby (non-interacting) Anderson localization is speculated to transform into a finite temperature or finite coupling metal-insulator transition in the presence of particle interactions22,23. We are investigating this putative transition via a variety of numerical approaches.

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Quantum 1 Quantum 2 Quantum 3
(E) Charge and Energy Transport in Nanoscale Systems for Efficient Energy Conversion

Under the auspices of Columbia’s Energy Frontier Research Center (EFRC) we are carrying out theoretical research aimed at optimizing the conversion of solar radiation to electrical energy. Our areas of focus combine techniques we have developed in areas (A) and (C) above. In particular, we are using methods from quantum relaxation theory (e.g. non-equilibrium Green’s functions and reduced density matrices) married with methods from electronic structure theory to investigate charge multiplication in nanotubes and other nanostructures, as well as exciton fission in organic materials. We are also investigating how phase and microphase separation may be optimized for the formation of bulk heterojunction devices.

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Energy 1 Energy 2
(F) Biophysical Transport

Our group has maintained an interest in biological transport problems such as how proteins find active sites along DNA24 and how biological cargo diffuse inside the crowded cellular environment25. Some of this work has been motivated and carried out with various experimental groups at Columbia, such as the Greene Lab (Columbia Medical School) and the Prives Lab (Columbia Biology).

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Bio 1 Bio 2 Bio 3