Events

[Seminar] : Moiré matters: Tuning light-matter interactions in twisted stacks of layered materials

Speaker: Dr. Medha Dandu, Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bangalore.

Title: “Moiré Matters: Tuning light-matter Interactions in twisted stacks of Layered Materials”

Date: Thursday, February 20th, 2025 – Time: 3:30 PM

Hi-Tea & Coffee: 4:30 PM

Venue: CeNSE Seminar Hall

Abstract:

Layered materials such as transition metal dichalcogenides (TMDs) host excitons with large binding energies and exhibit strong light-matter interactions making them an attractive platform for next-generation optoelectronics. Such layered materials allow the creation of designer heterostructures with atomically sharp interfaces, enabling precise control over band engineering, charge and energy transport for modulating excitonic properties. While often compared to nanoscale LEGO, the effects of interlayer coupling reveal intriguing phenomena beyond this simple analogy and can be tuned using a range of interdependent parameters such as twist and strain. By precise rotational alignment of the layers, nanoscale moiré superlattices can be realized to form periodic arrays of localized excitons, where one can control their arrangement and interactions to emulate quantum phenomena.

In this seminar, I will discuss the effects of interlayer coupling and moiré-induced excitons in twisted TMD bilayers, through optical spectroscopy. Further, I will present nanoscale imaging of such moiré excitons through correlative electron microscopy investigations. I will discuss the observations of interplay between the intrinsic lattice strain, atomic reconstruction, and moiré potential landscape on the energy and spatial distribution of excitons and how strain engineering provides an additional degree of freedom to tune moiré superlattices. I will also present a facile in situ tensile testing platform for 2D materials inside a TEM.

Biography:
Dr. Medha is an Assistant Professor at the Chemistry and Physics of Materials Unit (CPMU) in JNCASR since November 2024. Her research focuses on understanding and tuning the optical and optoelectronic properties of 2D materials, their heterostructures, and hybrid interfaces with emerging nanomaterials, using optical spectroscopy and correlative microscopy techniques. Before joining JNCASR, she worked as a postdoc in the Molecular Foundry at the Lawrence Berkeley National Laboratory. Earlier, she worked as a research engineer at the Centre for Development of Telematics, Bangalore (2014-2015). She obtained Ph.D. (and M.E.) from the Indian Institute of Science (2015-2022) and B.Tech. from NIT Warangal (2010-2014) in Electrical Communication Engineering. She received the Seshagiri Kaikini medal from IISc for best Ph.D. thesis-2022 in ECE.

Host Faculty: Prof. Chandan Kumar