Student Seminar

Name: Ms. Barnali Mondal

Title- Optical cavity-controlled phase transition in transition metal compounds

Date & Time: Thursday, 22nd February at 4.00 p.m.

Venue: Rajarshi Bhattacharya Memorial Lecture Hall, Chemical Sciences Building


The utilization of strong light-matter coupling within an optical cavity offers a distinctive platform for manipulating certain characteristics of matter, including phase transitions in transition metal compounds. These phenomena are embodied in confined light-matter hybrid modes termed polaritons—excitations of polarizable media, which are classified according to the origin of the polarization. Within this framework, quantum fluctuation of light and matter can altogether induce or enhance specific material properties.

In my presentation, I will start with a brief introduction of hybrid polaritronic states and their emergence from the light-matter interaction. Subsequently I will try to show the relevant cavity-electrodynamics and experimental realization through a simplified Jayens-Cummings Model. The presentation will then explore how the established theory is focussed on controlling the thermodynamics and macroscopic transport properties of quantum materials by engineering their electromagnetic environment; and can be implemented in an experimental set-up of a transition metal compound placed in a cryogenic terahertz cavity. By mechanically tuning the distance between the cavity mirrors and their alignment in the optical cavity, it is possible to achieve a precise control over the first orderphase transition between conducting and insulating phases. Finally, I will try to show how this coupling of light fluctuation and material resonance can extend to introducing an equilibrium phase in material rather than solely enhancing it, even in the absence of light. Overall, the objective of this presentation is to understand the effect of light-matter interaction in controlling quantum states of material which further enables the tailoring of materials properties and the potential design of novel materials purely by exposing them to confined light.


Jarc G., Mathengattil S.Y., Montanaro A. et al. Cavity-mediated thermal control of metal-to-insulator transition in 1T-TaS2. Nature 622, 487–492 (2023).
Latini S., Shin D., Sato S. A. et. al. The ferroelectric photo ground state of SrTiO3: Cavity materials engineering. PNAS, Vol. 118 (2021).