Phase Transitions and Elusive Electronic States In Correlated Oxides
Abstract
The physics of correlated electron systems is rich, and many phenomena discovered in these materials elude a thorough understanding. Of special interest is a host of phase transitions among diverse electronic and magnetic states in correlated electron oxides. These phase transitions can be controlled by various external stimuli, offering potential for future technologies. The present experimental picture of phase transitions in oxides is incomplete. The proposed program is focused on correlated electron systems where spin-orbit (SO) coupling plays a major role in the formation of enigmatic electronic and magnetic states. It is well established that SO coupling can trigger non-trivial band topology in weakly interacting system commonly referred to as topological insulators. These systems show unusual properties including robust surface states that are protected by topological properties of their bulk wave functions. Transition metal oxides where electronic correlations and SO interaction are equally important are predicted to uncover a myriad of novel electronic phases. Hence, oxides with strong SO coupling are at the forefront of current research in quantum materials. The significance of the proposed experimental program: the PI will address and resolve a number of pressing issues in the physics of transition metal oxides with strong SO coupling. Notably, novel electronic phases emerging near phase transitions in this class of materials are elusive since they only occur in a small fraction of a specimen. Therefore, a thorough understanding of phase transitions cannot be reached without an extensive use of local probe techniques needed to fully characterize a rich nanoscale landscape. The nano-optical methods developed by the PI enable access to optical properties with 5-10 nm spatial resolution, deep below the diffraction limit, and are therefore uniquely suited for the task. The key objective of the program is to carry out nano-infrared (nano-IR) studies of correlated oxides with SO coupling in the vicinity of the insulator to metal transition. The PI will exploit several complementary mechanisms to tune the transition including: temperature, in-situ coating with potassium atoms, photo-excitation and hetero-structuring. In combination, these experiments will produce a comprehensive experimental picture of various pathways from a correlated insulator to unconventional metal. The nano-optics approach is novel and has not been utilized by other practitioners in the field primarily because appropriate cryogenic nano-IR instrumentation cannot be acquired commercially and requires years of technical development. The PI will investigate single crystals, thin films and hetero-structures of several oxides with 5d electrons where the impact of SO interaction is expected to be especially prominent including: R2Ir2O7, Sr2IrO4, and Cd2Os2O7, where R is a rare earth element. Thin films of the 3d correlated oxide NdNiO3 where SO coupling is weak will serve as an important reference. Amidst phase coexistence and competition that are commonplace both in 5d and 3d correlated oxides, the clearest physical picture frequently demands a nano-scale perspective. The proposed nano-infrared studies will deliver a complete experimental picture of the electromagnetic response in these systems, particularly across the insulator to metal transition. The requested funding will be primarily used to support two graduate students who will perform both static and pump-probe nano-infrared experiments. This funding will support training for these researchers in the area at the crossroads of condensed matter physics and optics. Expertise in this particular area is in high demand in academia, government laboratories and in industry.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 16, 2018
- Source ID
- W911NF1710543
Entities
People
- Dmitri N. Basov
Organizations
- Army Contracting Command
- Columbia University
- United States Army