Tutorial NM06: Manipulation and Detection of Physical Properties of Two Dimensional Quantum Materials

The research on two-dimensional (2D) layered quantum materials such as twisted graphene, van der Waals bonded transition metal halides and chalcogenides, and other materials such as topological insulators and Weyl semiconductors has been rapidly progressing due to their intriguing magnetic, electronic, electrochemical, superconducting and optical properties and potential applications. The main focus of this tutorial is to discuss the advanced state-of-the-art experimental tools such as optical spectroscopy, pressure and in situ electrochemical characterization methods used to manipulate, control and measure the physical properties (magnetic, superconducting, electrochemical, opto-electronics, etc.) of quantum materials, heterostructures and devices, whose response is exceedingly difficult to detect by employing conventional bulk techniques. This tutorial will enable in bringing together scientists and engineers at all level, and in particular, young scientists and early career investigators practicing the physics, chemistry, materials science and engineering aspects of quantum materials, and expose them to cutting-edge research tools. 

Optical Spectroscopy—2D Materials
Archana Raja, Lawrence Berkeley National Laboratory

Optical spectroscopy is a powerful tool to study nanoscale materials, and in particular atomically thin 2D materials that exhibit extraordinarily strong light matter coupling in 2D materials. In this tutorial, Raja will introduce the optical spectroscopy of 2D transition metal dichalcogenides that are layered semiconductors, and the concept of excitonic Rydberg states to non-invasively understand electronic processes in these materials. In particular, Raja will discuss how excitonic states can be a probe of local strain, doping, dielectric screening and interfacial magnetic exchange. Technical aspects of micro-spectroscopy will be covered along with an overview of advanced capabilities available at national labs that can enable unique insights through correlated, multimodal measurements. 

Quantum Materials—Under Pressure
Sergey Budko, Ames Laboratory

Pressure is known to control the physical properties of quantum materials. This tutorial will focus on the hydrostatic and uniaxial pressure spanning from general principles to pressure cells design. This includes hydrostaticity, pressure media, experimental techniques under pressure/strain. In particular, this tutorial covers the properties of quantum materials such as superconductors, fragile magnets, novel semimetals under pressure. 

Electrochemical Properties—In Situ Characterization
Judy Cha, Yale School of Engineering and Applied Science

Many layered materials have been explored as electrocatalysts for various energy-relevant reactions, most notably for hydrogen evolution reaction (HER).  This tutorial will provide basic information on electrochemically driven HER, such as the reaction pathways, mechanisms, and standard experimental set-ups, and present our current understanding of the active sites of layered materials, mostly focusing on transition metal dichalcogenides.  The tutorial will discuss the effects of hydrogen adsorption energy, density of catalytically active sites, and catalyst-support interface on the overall activity of HER.  Moreover, the tutorial will highlight in situ characterization techniques and HER studies based on nanoscale devices, which can provide detailed information on the effects of microstructure and transport properties on HER during reaction.