3D Negative Electronic Compressibility as a New Emergent Phenomenon

This paper was written in honor of Prof. Ted Geballe's 100th birthday. It concerns a new emergent phenomenon called three-dimensional negative electronic compressibility. The physical content, driving mechanism, and context of the initial discovery of this phenomenon in an iridate material are reviewed. An integrative approach based on multiple experimental methods for carrier concentration modulation and chemical potential shift measurement is proposed for the quest of this phenomenon in other materials. Its implications on the physical properties of materials, in particular terms of electrostatic screening and phase separation, are discussed along with some of its unique prospects for applications.