B.S., 1977, California Institute of Technology. Thomas J. Watson Fellow, 1977-78. William Lowell Putnam Fellow, 1976. Ph.D., 1983, Harvard University. Postdoctoral Research Associate, Bell Laboratories, 1983-85. Research Associate, Cornell University, 1985-87. Assistant Professor, Physics, Boston University, 1987-89. Assistant Professor, Physics, Cornell University, 1989-93. Associate Professor, Physics, Cornell, 1993-2001. Professor of Physics, Cornell, 2001-present. Alfred P. Sloan Fellow, 1987-91. Fellow, American Physical Society. 

Research Areas
Theory of frustrated magnetism (classical and quantum), interacting electron systems, quasicrystals, and biological physics

Current Research

My research falls into the areas of frustrated magnetism (classical and quantum), interacting electron systems, quasicrystals, and statistical/biological physics.  Much of my work is geometrical, involving nontrivial patterns in space.

In biological physics, I am interested in pattern formation and mechanics in biology, specifically a large project about the physical bases of left/right symmetry-breaking in various animals (e.g. snails), in plants, or in assemblies of single cells.
I have also been interested in the capsid (exterior shell) geometry of viruses, and we model the mechanics of plant roots as imaged in current experiments at Cornell [undergrad Tzer-Han Tan and others].

In magnetism, we pursue the statistical physics and/or the quantum ground state of highly frustrated antiferromagnets on the Kagome, Pyrochlore and related lattices containing corner-sharing triangles, including the classical ground states. Some current projects are
(1) using the endlessly branching "Cactus lattice" as a surrogate for the Kagome lattice [Changlani, Lamberty] and
(2) mediated spin-spin couplings induced by interactions with a conduction electron sea [Ghosh]
(3) theory of NMR experiments on "spin ice" compounds (which have emergent "magnetic monopoles") [CLH].

We have recently worked out simple realizations of exotic “topological order”
in classical (rather than quantum mechanical) systems [Lamberty], and studied quantum spins on percolation clusters [Changlani, Ghosh].

In interacting electron systems, I work the border of analytic theory and computation. We are studying the (highly degenerate) ground states of a spinless fermion lattice model with “supersymmetry”
[with Dr. Stefanos Papanikolaou, now at Yale, and Dr. Dimitris Galanakis, Singapore]. We work on the phenomenology of STM measurements on high-Tc cuprates [Dr. Sumiran Pujari, now at Toulouse].

In quasicrystals, we want to determine the atomic structure and understand why quasicrystals form, using microscopically-derived interatomic potentials [visitor Dr. Marek Mihalkovic, grad Woosong Choi].
In particular, we want to (a) decide whether "matching rules" are responsible for the order in stable quasicrystals and (b) predict novel compositions of quasicrystal, beyond the 4 or so known classes.
Another side is the statistical physics of "random tiling" models, a likely explanation of the well-ordered icosahedral quasicrystals, and close packings of unequal spheres as a mathematical toy model related to structure prediction.

Graduate Students
Zach Lamberty, Hitesh Changlani (shared w/Umrigar), Shivam Ghosh

Also associated: Woosong Choi (Sethna group)

Undergraduate Students
Tzer-Han Tan