Seminars Archive

Designer Quantum Phenomena: From 2D ‘ferrolectric’ metal and magnetic electron liquid to new artificial nickelates

Abstract
Complex oxides with correlated electrons are a class of materials characterized by multiple competing and nearly degenerate ground states due to interactions that create a subtle balance to define the lowest energy state. This notion leads to a wide diversity of intriguing properties ranging from high Tc superconductivity to exotic magnetism and spin and orbit entangled phenomena. By utilizing the bulk properties of these materials as a starting point, interface between different classes of correlated oxides combined with geometrical lattice engineering offer a unique opportunity to break the fundamental symmetries of bulk and devise novel many-body and topological phases. These designer structures with enhanced electronic correlations, spin-orbit coupling, and lattice geometries supporting frustrated magnetic interactions can serve as a remarkably fertile ground for unusual quantum states of matter. Using our recent advances in complex oxide growth with the atomic layer precision, we can now combine layers of materials with distinct and often antagonistic order parameters to create novel artificial quantum materials. The broken lattice symmetry, strain, and altered chemical and electronic environments at the interfaces then provide a unique platform to manipulate this subtle balance and enable novel quantum states. Understanding of these phases, however, requires detailed microscopic studies of the heterostructure properties. To illustrate these challenges and opportunities, I will address the issues of manipulating magnetic interactions on the nanoscale and understanding the behavior of spins in the ultimate 2D limit, modulated carrier density, and orbital polarization. I will demonstrate the examples of realization of a magnetic 2D electron liquid and the first ferroelectric 2D metal. In addition, I will present our new class of nickelate heterostructures which finally help to unrival the 30 year old puzzle about the origin of the metal-to-insulator transition in rare earth nickelates.