MSE Department Seminar

Interfaces of two dimensional (2D) van der Waals (vdW) crystals constitute the most versatile material platforms for the exploration of new physical phenomena, particularly emergent quantum phases. Here we apply femtosecond pump-probe spectroscopy/microscopy to develop a time-domain view of quantum phases at 2D vdW interfaces of semiconducting, ferro/antiferro-magnetic, and ferroelectric materials. For transitional metal dichalcogenide (TMDC) moiré interfaces, we show the robustness of correlated electron phases and their coupling to phonons.

Multi-dimensional Coherent Terahertz Spectroscopy (THz-MDCS) is a new tool for studying with unprecedented resolution and for controlling quantum materials, by using a pair of phase-locked, intense Terahertz (THz) laser pulses. Establishing this experimental technique in superconductors and topological materials requires solving a non-equilibrium many-body problem that spans across several fields of current interest, including light-induced superconductivity, parametric driving of metastable phases, and quantum entanglement of supercurrent qubits.

In this talk, I will discuss several symmetries in quantum physics that have recently led to the observations of intriguing optical phenomena and the realizations of novel photonic functionalities. Different from canonical quantum mechanics, these symmetries imply non-Hermiticity that is difficult to realize in high-energy physics or condensed matter systems in a controlled fashion.

Fast ion conducting glasses have long been considered as alternatives to flammable liquid electrolytes in Li batteries. However, to date, there has never been before the unique combination of required electrochemical properties in any one such glass for its use as a solid electrolyte with the equally important requirements of viscoelastic behavior to form them into thin films suitable for high ion conductivity separators.

Following molecular-level chirality studies, the chirality of nanomaterials is a newly emerging focal point in the field, catalyzed by the discovery of intense polarization rotation in individual nanoparticles (NPs) and their assemblies.

Lithium-based batteries are essential in modern energy supply systems. There is a demand for safer and higher energy density batteries, and for securing the supply chain of Li for production of these batteries. In this talk, I will cover experimental and modeling studies that focus on the interactions among ions, solvents, and polymers in both battery and separation systems, and how these interactions can be optimized through molecular-scale design.

This year marks the 27th anniversary of IBM’s CMOS/Cu BEOL [Back End of the (manufacturing) Line] on-chip interconnect technology reaching production, with the first high-end Cu CPU chips passing manufacturing qualification and being sampled to customers. This announcement shocked the industry, who were unaware that Cu had been taken beyond the early research phase.

Innovative materials are needed to tackle current major challenges in energy storage and generation. However, the design of new materials largely relies on experimental trial and error, limiting the number explored compounds relative to the entire space of possible compounds. In this presentation, I will discuss our approach to materials design, which integrates machine learning (ML) techniques with quantum mechanics-based computations.

Advances in optics and in the harnessing of light-matter interactions have led to corresponding advances in coherent optical excitation and monitoring of collective degrees of freedom including transverse and longitudinal acoustic modes, optical phonons, and magnons both within and far beyond their linear-response regimes.

Despite being an old material in optical and microwave technologies in its bulk form, thin-film lithium niobate (TFLN) has recently emerged as one of the most promising integrated photonic platforms owing to its strong electro-optic (EO) coefficient, quadratic optical nonlinearity, and broadband optical transparency ranging from 350 nm to 5 µm. In this talk, I will first overview the basic optical properties of LN, and how LN nanophotonics can grant us new regimes for studying ultrafast and nonlinear photonics.