Research & Initiatives
Research Area 1
Hydrothermal and solvothermal synthesis of non-centrosymmetric Quantum Materials
Team Members: Huafei Zheng, Lahari Balisetty, Akil Mondie
What happens when you remove certain symmetries in the crystal structure of quantum materials? In particular, when one removes inversion symmetry. Our group synthesizes transition metal chalcogenides with layered-type structures in order to 'twist' or 'bend' them to make them non-centrosymmetric and induce new physical phenomena. Such a strategy could, for example, lead to novel pairing mechanisms in superconductors. To do this bending or twisting, we insert metal amine species between the chalcogenide layers, taking advantage of the van der Waals gap and hydrogen bonding of the type N--H-Q where Q= chalcogenide anion such as S2- or Se2-. The metal amine species is a chiral molecule itself such as M(en)3 where M = coordinating metal and en=ethylenediamine. With advanced scattering measurements that include synchrotron X-rays and neutrons, we study the key structure-property relationships of our materials. The layered host is typically a tetrahedral transition metal chalcogenide (TTMC) where MQ4 tetrahedra edge-share to make 2D layers. Below, a schematic our non-centrosymmetric quantum materials, which include chalcogenides of iron, cobalt, manganese and nickel.
This research project is currently supported by the National Science Foundation Division of Materials Research, DMR-2113682.
Research Area 2
Understanding the structure-property relationship of functional metal oxides to tackle the challenges in energy and environment
Team Members: Tianyu Li, Matt Leonard, Stephanie Hong
Metal oxides are one of the most common substances on the earth. Due to their diversity in structures, compositions, and properties, metal oxides are extensively used in production and life, ranging from construction materials to catalysts and electronic semiconductors. Our motivation is to understand the structure-property relationships of the metal oxides so that we can design better materials to tackle the energy and environment-related challenges.
One application we focus on is Oxygen storage materials for clean energy production. With the help of in-situ diffraction characterization, we study the structural evolution of the oxides under different chemical reaction cycles (Figure 1). Our goal is to correlate the material performance to the crystal structures and structural evolution behaviors.
The second application we are interested in is the filter materials to combat the Chemical Ware Fare agent. Our aim is to understand how the structures of the metal oxides influence their activities toward the adsorption and decomposition of Chemical Ware Fare agents such as sarin so that we can determine important factors for potential high-performance materials. Our primary approach is Operando Spectroscopy (Figure 2) and DFT simulations.
Figure 1. In-situ diffraction characterization of oxygen storage materials under oxidation and reduction cyles
Figure 2. In-situ IR spectroscopy characterization of surfaces of mesoporous oxide when interacting Nerve Agent Sarin moledules.
Research Area 3
Exploring 2D Magnetism in van der Waals Materials with Polarized Neutron Scattering
Team Members: Stephanie Gnewuch, Tim Diethrich, Ryan Stadel, Mario Lopez, Cein Mandujano
The world's dependence on electronics in all aspects of our lives is a fundamental reality. With looming climate concerns and ever-growing energy demands taxing our power grids to their limit, the need for faster and more efficient technology has never seemed more urgent. Electronic engineering (computer processors/storage/quantum computing/solar cells) relies on access to a wide selection of materials with tunable electronic and/or magnetic properties. Neutron scattering has been and remains an invaluable technique to probe the structure and dynamics of quantum materials. In which, understanding the charge, orbital, and lattice degrees of freedom is a necessary pre-condition for developing new materials with desirable properties and furthering our understanding of the fundamental physics that give rise to the technologies on which modern society is built.
Quasi two-dimensional (2D) van der Waals (vdW) materials offer exciting prospects in investigating the effects of reduced dimensionality on these quantum properties. Unlike other well-studied vdW materials such as graphene, transition metal chalcophosphates (TMCs) (M'M"P2Q6 where M' & M" are transition metals and Q is either S or Se) can incorporate magnetic ions and exhibit a wide variety of magnetic ordering (examples of which can be seen in Figure 1). But what makes these materials truly exciting is a varied selection of additional behaviors (often into the 2D limit) such as multiferroicity (Figure 2), orbital ordering, a Kitaev quantum spin liquid ground state, metal-to-insulator transitions, and superconductivity. By synthesizing polycrystalline and single crystal examples of these compounds with variations on M', M", and Q, and measuring them with a structural focus via polarized neutron scattering and neutron diffraction, our goals are twofold: we intend to identify materials for faster and more efficient next-generation electronics and to contribute significantly to the understanding of the basic physics of ordered electron behavior in the 2D limit.
Figure 1. The solved Magnetic structures of a) Ni2P2S6, b) Mn2P2S6, c) Fe2P2S6, d) Co2P2S6.
Figure 2. Examples of electrical polarization in multiferroic CuM''P2S6 compounds.
This work is funded by the DOE Basic Energy Sciences, Neutron Scattering Program, DESC-0016434