Umesh V Waghmare
President, Indian Academy of Sciences (IASc), Bengaluru
Umesh V Waghmare graduated with an Institute Silver Medal and a B.Tech. in Engineering Physics (1990) from IIT-Bombay. He received a Ph.D. in Applied Physics from Yale University, New Haven in 1996 and has carried out postdoctoral research at Harvard University (1996–2000). He joined JNCASR as an Assistant Professor in 2000. He was an Adjunct Professor at Birck Nanotechnology Center of Purdue University (2010–2012) and TIFR, Mumbai (2014–2017). He is currently a Professor in the Theoretical Sciences Unit, JNCASR (2009–present).
Session 1A: Inaugural Session and Presidential Address
Sensing Vibrations using Quantum Geometry of Electrons
After introducing basic ideas of quantum geometry of electronic structure of a crystal, we present a theoretical proposal of a new class of spectroscopies that connect with the ideas in Raman’s work (1924) and Pancharatnam’s work (1956).We show that the coupling of phonons with electrons can have nontrivial consequences for the quantum geometry of an electronic structure, which manifests as oscillations in the Berry curvature dipole and hence have observable nonlinear Hall signatures. Using these, we introduce a vibrational spectroscopy based on the geometry of quantum electronic structure (GQuES) making specific predictions for the transport and radiative GQuES spectra of two-dimensional materials. The selection rule presented here for the GQuES activity of a phonon allows the measurement of acoustic and optic phonons spanning sub-GHz, THz, and infrared frequencies, and is readily generalized to other dynamical excitations. GQuES can be used even for materials having trivial quantum electronic geometry, such as hexagonal boron nitride, through a proximal interaction with substrates such as graphene.