Disorder-to-order transition in selenium under cyclic compression-decompression

Amorphous solids, as long-range disorder materials, have complex order on multiple length scales. The regulation of the degree of order is generally achieved through annealing or static compression. Unlike previous studies, this work has triggered the disorder-to-order transition in amorphous selenium ($a$-Se) by cyclic compression-decompression in a dynamic diamond anvil cell. We found that the degree of order in the directionally bonded $a$-Se positively correlates with the number of compression cycles, and long-range order was achieved in a relatively low-pressure range. The possible transformation mechanism is discussed on the basis of medium-range structural parameter regulation. This work provides an understanding of the relaxation and extension of the order length scale by unconventional mechanical stimulation.