Quantum Materials and Complex States of Matter

Ames Lab is predicting, designing, and making new functional materials by manipulating electronic, atomic, and phase transformation behaviors. This requires unprecedented control over complex materials – thus our push, to understanding how every atom influences phase transformations. With this understanding, we will be able to design and control materials – to reveal behaviors, to control the mechanisms, and ultimately produce new properties and functionalities.

We will design, synthesize and control materials with novel functionalities, ranging from metamaterial control of electromagnetism to multiferroic materials that couple multiple fields. We will create novel materials that reveal the role of disorder and defects in controlling competition between states. For example, our recent work on CaKFe4As4 shows a novel antiferromagnetic state, and provides a unique opportunity to examine the competition between antiferromagnetism and superconductivity in the absence of chemical disorder.

We will achieve exquisite control over the thermodynamics and kinetics of solid-state phase transformations, to create materials with new properties and functionalities. In particular, we will understand the role of bonding, atomic structure and composition, and defects not only in the thermodynamic behavior, but on the far-from-equilibrium behaviors associated with hysteresis and metastability that affect functionality. By harnessing the coupling of phase transformations to magnetic and quantum phenomena, we can go beyond “static” behavior to achieve significantly greater response. Depending on the system, the transformations may be controlled through magnetic fields, pressure, as well as more complex strain states that alter local symmetries and can bias variant selection during transformations. We will understand these transformations, and utilize them to create highly responsive materials. We will examine and control the effects of hysteresis: some functionalities, such as solid-state caloric materials, require minimal hysteresis. The ability to tune lattice parameters, composition, defects, and microstructure are fundamental to hysteresis; designing and harnessing these to affect hysteresis remains a major challenge.

We will also tackle the challenge of harnessing metastability: through controlling kinetic traps and barriers to transformations – through composition, through interfacial control – we can better target and create structures with desirable behaviors. We are developing theoretical approaches to map out transformations, and to understand the role of defects and disorder in controlling these. We will utilize both theory and experiment to create the ability to target a particular crystal structure – for example, by utilizing minor elements that can stabilize a desired structure – enabling the formation of new materials with new properties. 

Ultimately, we will achieve a “materials by design” strategy that controls and harnesses metastability to create desired crystalline structures with anticipated properties, which incorporates phase transformations and associated hysteresis into functionality, utilizing all degrees of freedom – stress, electronic, magnetic, atomic, and microstructure – to enable robust, responsive capabilities for next generation technologies.