Two-dimensional crystal of several millimeter size spheres

Two-dimensional crystal is tested in the system of several millimeter size polystyrene spheres. Large numbers of same size spheres are triboelectrically charged through rubbing on the substrate plate. Therefore, one can observe the two-dimensional system without the help of any instrument and can easily micro-control the condition of two-dimensional system. The Fourier transform spectra, the pair distribution and the bond-orientational correlation function data show that the system is in near hexatic phase after fully charged, which is predicted by the KTHNY theory.