Temperature Dependent Nanoscale Structural Distortions in PbTe and PbS
Conventional structural phase transitions are characterized by a symmetry lowering rearrangement of the atoms in a crystal upon cooling. New research has discovered the opposite behavior--a dynamic local ferroelectric-like symmetry breaking that appears at high temperatures in the binary lead chalcogenides, PbTe and PbS. This intrinsic response is a new phenomenon that has been dubbed emphanisis. These materials, which were previously believed to adopt an ideal, undistorted rock-salt structure at all temperatures, are important because of their thermoelectric properties. This discovery is key to understanding the strong thermoelectric response of these materials and could help scientists search for other thermoelectric materials with exceptional properties.