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Quantum Materials

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What are Quantum Materials? #

These are materials where the extraordinary effects of quantum mechanics give rise to exotic and often incredible properties. While all materials exhibit quantum mechanical properties at some level, ‘quantum materials’ exhibit unique properties like quantum fluctuations, quantum entanglement, quantum coherence, and topological behavior.

Our Focus #

A central focus of our research group is to describe, from first principles, the microscopic dynamics, decoherence and optically-excited collective phenomena in materials at finite temperature (that is, including phonons ab initio) to quantitatively link predictions with 3D atomic-scale imaging, quantum spectroscopy and (subsequently) macroscopic device behavior. Capturing these dynamics poses unique theoretical and computational challenges; the simultaneous contribution of processes that occur on many time and length-scales have remained elusive for state-of-the-art computational materials and model Hamiltonian approaches alike, necessitating the development of new methods.

The physics of quantum materials is rich with spectacular excited-state and nonequilibrium effects, but many of these phenomena remain poorly understood and consequently technologically unexplored. Our research, therefore, focuses on: how do quantum-engineered materials behave, particularly in their excited and nonequilibrium state, and how can we harness these effects? By developing predictive theoretical and computational approaches to study dynamics, decoherence and correlations in materials, our work will enable technologies that are inherently more powerful than their classical counterparts ranging from scalable quantum information processing to ultra-high efficiency optoelectronic and energy conversion systems. At the quantum limit, these technologies could underpin the next revolution in our world’s energy, computing and information infrastructure. To enable this ambitious program, our group is inherently interdisciplinary: we work across high-performance computing, materials theory, condensed matter physics, and computational chemistry and collaborate closely with experimental groups to connect predicted properties with cutting-edge measurements.

Low Dimensional Quantum Materials #

2D materials and van der Waals heterostructures allow us to play with legos at an atomic-scale. These stacked 2D materials or van der Waals heterostructures have generated considerable recent interest as designer photonic and optoelectronic quantum materials. Much like legos, they could stack perfectly or be slightly mismatched (strained) or have strong mismatch effects like Moire periodicity. The ability to directly fabricate structures with atomic precision suggests a new path toward realizing more resilient quantum devices. However, so far, work in this field has been led by experiments and concomitant simulations. This is where our work comes into the picture! We are developing computational tools and a predictive understanding of quantum materials. Combining the power and possibilities of excited-state and heterostructure engineering with the collective and emergent properties of quantum materials, quantum-matter heterostructures open a new field of materials physics.

Linear-, Nonlinear-, and Hydrodynamic- Quantum Materials #

A central problem in electronic structure simulations of excited states is capturing the dynamical interaction of electrons and phonons in quantum materials without approximating the phonon behavior. While much work has been done on the analytical treatment of the electron-phonon interaction, a computational implementation is essential for prediction of lifetimes and transport in real materials. To this end, our group has pioneered the field of ab initio calculations of phonon-assisted excitations in metals, Weyl semimetals and mixed dimensional-layered quantum materials and led the field in calculations of energy-dependent lifetimes and mean free paths of excited carriers, accounting for electron-electron and electron-phonon scattering. This work has provided essential theoretical insight into transport in materials showing hydrodynamic electron flow as well as in characterizing non-equilibrium and optically-generated carrier dynamics including linear and nonlinear processes at the nano-mesoscale. In tandem, we have introduced a new transport framework to study phonon transport across semi-coherent and coherent interfaces, retaining atomic-scale detail and microscopic scattering information.