Fachbereich für Physik, Universität Konstanz, D-78464 Konstanz, Germany.
Phys Rev Lett. 2013 Aug 30;111(9):098301. doi: 10.1103/PhysRevLett.111.098301. Epub 2013 Aug 27.
We study the influence of quenched disorder on the two-dimensional melting behavior of superparamagnetic colloidal particles, using both video microscopy and computer simulations of repulsive parallel dipoles. Quenched disorder is introduced by pinning a fraction of the particles to an underlying substrate. We confirm the occurrence of the Kosterlitz-Thouless-Halperin-Nelson-Young scenario and observe an intermediate hexatic phase. While the fluid-hexatic transition remains largely unaffected by disorder, the hexatic-solid transition shifts to lower temperatures with increasing disorder. This results in a significantly broadened stability range of the hexatic phase. In addition, we observe spatiotemporal critical(like) fluctuations, which are consistent with the continuous character of the phase transitions. Characteristics of first-order transitions are not observed.
我们使用视频显微镜和排斥平行偶极子的计算机模拟来研究淬火无序对超顺磁胶体粒子二维熔化行为的影响。通过将部分粒子钉扎到底物上来引入淬火无序。我们证实了 Kosterlitz-Thouless-Halperin-Nelson-Young 情景的发生，并观察到中间六方相。虽然无序对流体-六方相转变的影响不大，但六方相-固相转变随着无序的增加而向低温移动。这导致六方相的稳定性范围显著变宽。此外，我们观察到时空临界（似）涨落，这与相变的连续性质一致。没有观察到一级相变的特征。
