Non-equilibrium dynamics of interacting systems

Aditi Mitra, New York University, DMR 0705584

One of the least understood areas of physics is how strongly interacting systems behave when they are driven far out of equilibrium. We studied two systems which were driven out of equilibrium by a sudden change in system parameters. The first system (Fig. A) was a nanoscale device consisting of a spin coupled to two reservoirs. When the couplings to one of the reservoirs was suddenly changed, the local spin was found to relax very slowly (as a power-law in time) to equilibrium. On the other hand the spin of the full system comprising of the reservoir and local spin was found not to reach equilibrium at all. Similar lack of equilibration was seen in a chain of spins (Fig. B) . This slow equilibration or lack thereof is due to the presence of a large number of conservation laws in many interacting systems.

1 1

2

1J

tJ 2

A spin (represented by the arrow) iscoupled to two reservoirs (labeled 1,2)

A

B

yx

z

Spins initially arranged as follows

evolved at long times into the followingspiral pattern in the x-y plane

Non-equilibrium dynamics of interacting systems

Aditi Mitra, New York University, DMR 0705584

An important component of the research has been the training of graduate students via their active participation in projects. Project A (Phys. Rev. B, 81, 125110 (2010) ) was done with graduate student Zurab Ratiani who has now graduated and will soon start as a postdoctoral research scientist at the International Center for Theoretical Physics (Trieste, Italy).Project B (Phys. Rev. E, 81, 061134 (2010) ) was done with graduate student Jarrett Lancaster. Both these students have presented their work at several conferences.The projects have also involve the participation of traditionally under-represented groups such as women.