# Abstract

__MSc Ankush Sengupta__: „Dynamical structures in driven disordered systems”

S. N. Bose National Centre for Basic Sciences Kolkata, India

We study[1] the non-equilibrium steady states of a crystal whose
ground state can be tuned through a square-triangular transition.
Driving such a system across a quenched random background yields
a complex sequence of novel dynamical states: plastic flow,
anisotropic hexatics, dynamically stabilized triangle and square
phases and intermediate regimes of phase coexistence with
anamolously
slow dynamics. Finite size scaling arguments and defect structure
analysis estabish the reality of the hexatic phase, indicative of a
KT type freezing transition. We investigate analogy of our continuum
model with XY model in magnetic field. A detailed analysis of
relevant
orientation correlation functions and the drive induced anisotropy
shows evidence of novel mechanisms underlining the dynamical
freezing
transition. The behavior of topological defects shows a possible
connection to deconfinement in the two dimensional XY model. Noise
studies in coexistence phase shows highly correlated motion with 1/f
noise in statistical fluctuations and breakdown of the
Koshelev-Vinokur
proposal of shaking temperature. Dynamic nucleation under external
fields, as revealed in our model, is also explored. Such states, as
we btain, should be observable in transport experiments on the mixed
phases of several superconductors which exhibit related structural
transitions, and on adsorbed monolayer colloids with tunable
interactions.

Reference:

[1] Ankush Sengupta, Surajit Sengupta, Gautam I. Menon,

*Driven disordered periodic media with an underlying structural
phase transition.*

Phys. Rev. B **75**, 180201(R) (2007)