b'39Viktor Struzkhin (left), Jianjun Ying (right), and team discovered the unusual structural changes in the semiconductor tin diselenide, SnSe 2 , when it was subjected to pressure.Images courtesy Viktor Struzhkin(a) H1 (b) H2-1to, where electrons are located on a so-called Fermi surface. Fermi surfaces with nearly flat parts parallel to each other are described as the nesting condition.SeTypically, high pressure would suppress the nestingSncondition, destroying the distorted lattice structure and its charge density wave. But that did not happen.Instead, the researchers found that the Fermi nesting condition and strong electron-vibrational coupling occur under pressure with the same momentum and wave direction. This result agreed with their theoretical calculations, but differed from findings in similar materials where the Fermi nesting wasThis illustration compares the parent, undistorted structure (a) found to be less significant in creating the chargeof the semiconductor tin diselenide, SnSe 2 , to an out-of-plane density wave state. This surprising finding opens newdisplacement of the Sn atoms (grey) in the distorted structure (b). The distortion resulted in a slight buckling of the Sn layers opportunities for these materials.and a shift of the Se atoms (green), distorting the top-view (two images at bottom) hexagonal symmetry.Image courtesy Elena Margine'