First principles investigation on Quantum Materials
by Dr. Subhasish Mandal (Dept. of Applied Physics, Yale University)
Tuesday, April 4, 2017 from to (Asia/Kolkata)
Computer simulations based on first principles calculations play a central role in helping us understand, predict, and engineer physical, chemical, and electronic properties of technologically relevant materials. This can solve many problems towards building faster, smaller and cheaper devices for processing and storing information as well as for saving energy. Many of these processes involve electron excitations and strong local magnetic fluctuation that the ‘standard model’ of electronic structure, Density Functional Theory (DFT), can’t capture properly. In this context, I will highlight two popular approaches that go beyond the standard DFT. First, I will discuss how Dynamical Mean Field Theory (DMFT) in combination with DFT has recently been successful for detailed modeling of the electronic structure of many complex materials with strong electron correlation. To give an example, I will show the iron-based superconductors on both bulk and monolayer phases and their anomalous properties, which have their origin in strong Hund's coupling and give rise to the rich physics of Hund's metals. Next, I will discuss my collaborative effort toward developing a high scalable, open-source GW software to compute electronic excited states more efficiently for petascale architectures using the Charm++ parallel framework. At the end, I will briefly discuss topological crystalline insulators, which are a new class of topological materials where electronic surface states are topologically protected along certain crystallographic directions by crystal symmetry. I will show that, without any external perturbation, both massless Dirac fermions protected by the crystal symmetry and massive Dirac fermions with crystal symmetry breaking can coexist on a single surface.