New Opportunities on Phase Transitions of Correlated Electron Nanostructures

Correlated Electron Materials (CEMs) typically exhibit complex domain structures at the micro- to nanometer scales which greatly affect their physical behavior. Nanoscale specimens can be made smaller or comparable to their characteristic domain sizes, thus enabling detailed investigation into their intrinsic properties. VO2 is a representative CEM that exhibits coupled electronic and structural phase transitions. The phase transition in VO2 bulk and thin films features percolative, random domain structures, which result in averaged physical behavior in measurements. This chapter focuses on recent reports of nanostructured VO2 that has led to new discoveries and helps resolve many outstanding questions from bulk and thin film studies. The chapter specifically focuses on the following topics (1) origin of the phase inhomogeneity in VO2; (2) domain organization and manipulation; (3) driving mechanism of the phase transition; (4) superelasticity and mechanical properties; (5) new phase stabilization under stress; and (6) thermoelectric effects of the domain walls. The general nanostructures approach suggests a new pathway for investigating many complicated effects in a broad range of CEMs.