Complex structural phase transition in a defect-populated two-dimensional system

A. V. Melechko¹, M. V. Simkin^1*, N. F. Samatova², J. Braun^1§, and E. W. Plummer¹
 

 

¹Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
 

 

²Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831
 

A complex phase transition in Sn/Ge(111) and similar systems can be decomposed into two intertwined phase transitions: a structural symmetry lowering (sqrt[3] x sqrt[3])⇔(3 x 3) transition and a disorder-order transition in the defect distribution. We present two phenomenological models that describe these transitions and their interrelation. These models allow us to understand the formation of domains and domain walls at low temperatures, defect-induced density waves above the structural transition temperature, and ordering of the defects caused by lattice-mediated defect-defect interactions. The models predict a destruction of the pure structural transition when impurities are introduced into the system, a shift in the structural crossover temperature with impurity density, and a dependence of the (3 x 3) lattice structure on the specific defect alignment.

©2001 The American Physical Society

URL: http://link.aps.org/abstract/PRB/v64/e235424