Why has it been so difficult to arrive at a consistent theory of superconductivity in the high Tc cuprates?

More than three decades after the discovery of superconductivity in the cuprates, the nature of the “normal” state and the mechanism of superconductivity remain mysterious. In this talk I will present the viewpoint that theoretical efforts to understand cuprate superconductivity have missed the key concept of valence transition, that has been discussed previously in the context of materials as diverse as heavy fermions and organic donor-acceptor chargetransfer solids. I will point out that this concept allows us to construct a “global approach” to the slew of diverse “negative charge-transfer gap” materials. Following this I will present our recent work on the cuprate ladder superconductor Sr2−xCaxCu24O41, which provides strong support to our earlier application of the valence transition theory to pseudogap, chargeorder and superconductivity in the layered cuprates. Time permitting, I will discuss the application of the theory to Sr2RuO4.

How to design polymers to fulfil functions in solar cells, biosensors, and batteries?

: The main theme of the talk will be the principles of polymer architecture and structural changes in conjugated polymers, conjugated polyelectrolytes and polymer electrolytes to fulfil diverse properties in modern applications such as solar cells, biosensors, thermoelectrics as well as batteries. The diverse applications demand a wide variety of structural changes and adaptation of hydrophobicity and hydriophilicity in addition to tuning and optimization of charge transport from pure electronic or ionic conductors to mixed conductors. With suitable examples of polymers, the design principles and applications will be demonstrated in various devices. An additional aspect of doping of conjugated polymers and the consequences of a novel and stable p-doping strategy will also be discussed. References : 1. Solid polymer electrolytes from polyesters with diester sidechains for lithium metal batteries, D. Rosenbach, M. Thelakkat et al, J. Mater. Chem. A 2022, 10, 8932-8947. 2. Highly Efficient Doping of Conjugated Polymers using Multielectron Acceptor Salts; G. Krauss, M. Thelakkat, et al. Macromolecular Rapid Communications, 2021, 42, 2100443. 3. Polydiketopyrrolopyrroles Carrying Ethylene Glycol Substituents as Efficient Mixed-Ion Conductors for Biocompatible Organic Electrochemical Transistors; G. Krauss, M. Thelakkat,; Adv. Funct. Mater. 2021, 31, 2010048. 4. The Key Role of Side Chain Linkage in Structure Formation and Mixed Conduction of Ethylene Glycol Substituted Polythiophenes; P. Schmode, M. Thelakkat, ACS Appl. Mater. Interfaces, 2020 12, 13209- 13039

Living in the World of RNA Therapeutics

Crystal Engineering. Its Potential in Modern Chemistry and Society

Nonlinear vibrational spectroscopy of aqueous solutions and its relations to underlying structure and dynamics

We will discuss our recent studies of nonlinear vibrational spectroscopy of aqueous solutions using a combination of classical molecular dynamics, ab initio quantum calculations and spectral mapping methods. Specifically, we will present a brief overview of our calculations of oneand two-dimensional infrared spectroscopy including those of surface specific vibrational sum frequency generation spectroscopy of stretch modes of water in the mid-IR region and how our theoretical results compare with available experiments in the literature.

Quantum Entanglement: from a small step to a giant leap

Quantum mechanics is weird: it is probabilistic and non-local. I will start with a gentle introduction to quantum entanglement, explain how it has heralded a new paradigm in understanding quantum materials, and how it will potentially be used to make topological qubits for quantum computation.