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Instabilities and Functional Properties of Crystals


Title : Instabilities and Functional Properties of Crystals.
Speaker : Prof. Umesh V. Waghmare, Theoretical Sciences Unit, J Nehru Center for Advanced Scientific Research (JNCASR), Bangalore
Date : 19/10/2022, 05:30 PM , C V Raman Hall, IISER Tirupati Transit Campus.

Abstract:  Properties of a crystalline material are fundamentally determined by its electronic and atomic structure. Some crystals host instabilities that cause sharp changes in the structure with external field while preserving their rigidity. Symmetry breaking at such a structural transition is responsible for the emergence of their technologically important functional properties. For example, applications of a ferroelectric crystal in sensors, speakers or in memories are possible due to piezoelectricity and switchable dipole moments it exhibits as a consequence of broken inversion symmetry at a ferroelectric transition. Functional properties of advanced materials have their roots in many of various instabilities. Development of advanced functional materials is thus facilitated by material-specific understanding or a theory that captures the interactions between instabilities with respect to various symmetry breaking structural modes and their coupling with external fields. To this end, we introduce a standard model of materials, and demonstrate how first-principles quantum and statistical mechanical theoretical analysis of instabilities can effectively give predictive model of material-specific behavior. We illustrate this with instabilities of polar phonons, spin-ordering and strain that drive functional properties of ferroelectric, antiferromagnets and shape memory alloys respectively, which have tremendous potential for applications in sensor, actuators and micro-electromechanical devices.

About the Speaker: Prof. Umesh V. Waghmare graduated with an Institute Silver Medal and a BTech in Engineering Physics (1990) from IIT-Bombay. He received a Ph.D. in Applied Physics from Yale University, New Haven, in 1996 and conducted postdoctoral research at Harvard University (1996-2000). He joined JNCASR as Assistant Professor in 2000; since 2009, he has been a Professor in the Theoretical Sciences Unit. He had been an Adjunct Professor at Birck Nanotechnology Center of Purdue University (2010-2012) and TIFR, Mumbai (2014-2017).  Currently, he is the Dean of Faculty Affairs at JNCASR. He is a fellow of the Indian National Science Academy, Indian Academy of Sciences, and National Academy of Sciences. He is a recipient of several awards and fellowships, which include the Infosys Science Prize, the J.C Bose fellowship, and the Shanti Swarup Bhatnagar Prize.

Prof. Waghmare has significantly contributed to the following areas: Ferroelectrics, Electronic Topological Transitions, Nano-scale Materials, Mechanical Deformation of Materials, Multiferroics and Dilute Magnetic Semiconductors, Materials for Energy and Environment, and the Development of Formalism and Methods.