Johari-Goldstein relaxation far below Tg: Experimental evidence for the Gardner transition in structural glasses?

摘要

Experimental evidence for the Gardner transition, theoretically predicted toarise deep in the glassy state of matter, is scarce. At this transition, theenergy landscape sensed by the particles forming the glass is expected tobecome more complex. In the present work, we report the dielectric response oftwo typical glass formers with well-pronounced Johari-Goldstein beta relaxationfollowing this response down to unprecedented low temperatures, far below theglass transition. As the Johari-Goldstein process is believed to arise from thelocal structure of the energy landscape, its investigation seems an ideal toolto seek evidence for the Gardner transition. Indeed, we find an unusualbroadening of the beta relaxation below TG ~ 110 K for sorbitol and TG ~ 100 Kfor xylitol, in excess of the expected broadening arising from a distributionof energy barriers. Thus, these results provide hints at the presence of theGardner transition in canonical structural glass formers.