• Complex oxides and heterostructures

Screen Shot 2016-08-09 at 2.39.22 PMThe polar mismatch at the interface of complex oxides leads to the formation of a two-dimensional electron gas (2DEG), such as in SrTiO3/LaAlO3 and SrTiO3/GdTiO3.  Computer simulations based on first-principles methods are used to investigate the fundamental properties of the 2DEG, in particular the variation of the 2DEG density with the thickness of the top LaAlO3 layer, the metal to insulator transitions in the limit of ultra-thin layers, the effects of octahedral rotations at the interface, and the possible role of strong electronic correlations.



  • Transparent conducting oxides (TCOs)

First-principles calculations are employed to advance our Screen Shot 2016-08-09 at 2.38.57 PMunderstanding of the basic optical and electrical properties of TCOs,  addressing the variation of the carrier effective mass and mobility with doping concentrations, the effects of extremely high doping levels.  Calculations are performed to determine the fundamental parameters that give high transparency in the visible and high conductivity, as well as the processes that govern light absorption in the infrared and ultraviolet limits. 



  • Resistive switching electronic materials 

Resistive switching phenomena have been observed in many oxides, e.g., in Screen Shot 2016-08-09 at 2.51.14 PMTiO2, Cr2O3, NiO, (Ba,Sr)TiO3, Ta2O5, HfO2, Al2O3, Gd2O3, WO3, MoO3, and ZrO2First-principles calculations are used to reveal the microscopic mechanisms that lead to the formation and rupture of conductive filaments, the role of point defects, the formation of oxygen-deficient phases, and the effects of charge localization in the form of small polarons, Understanding the basic mechanisms behind the resistance switching will certainly aid in improving device performance.


  • Multifunctional Heusler materials

Picture1Single crystal thin films demonstrate the presence of a topological surface state with spin-momentum locking in the diverse Heusler compound family. This  provides a multitude of new approaches for spintronic devices which make use of combining a wide range of electronic structures without changing crystal structure. Firs-principles calculations are used to understand the fundamental mechanisms of band inversion and surface states in this rich family of compounds.