Novel Quantum Phases in Heavy d- and f-electron Systems Studied Using Nonlinear Optics
Abstract
The scientific objective of this research project is to experimentally identify novel symmetry-broken quantum phases of matter that arise through a combination of strong electron-electron correlations and strong spin-orbit coupling and to understand the microscopic mechanisms through which they emerge. In strongly correlated electron systems, symmetry breaking typically occurs through a spatial modulation of charge, electric dipole moment or magnetic dipole moment densities, which are associated with phenomena such as charge ordering metal-to-insulator transitions, ferroelectricity or antiferromagnetism, respectively, that are commonly observed in 3d and 4d-electron systems. However, in the presence of strong spin-orbit coupling, ions on each lattice site can support higher rank electric and magnetic multipolar moments that undergo long-range ordering phase transitions. Exotic multipolar ordered phases are proposed to be pervasive among 4f and 5f-electron systems and have more recently been postulated in 5d electron systems. Multipolar physics is predicted to underlie a variety fundamental condensed matter phenomena including hidden order (non-dipolar) phase transitions, non-magnetic Kondo effects, unconventional Mott insulator-to-metal transitions and non-BCS type heavy fermion superconductivity. However, multipolar ordered phases are very challenging to experimentally identify because they are described by tensor electronic order parameters whereas most probes of condensed matter are primarily sensitive to scalar or vector electronic order parameters. Several probes, most notably resonant x-ray diffraction, have provided important demonstrations of the existence of multipolar order in a few materials. However there is need to develop novel instrumentation that directly couples to electronic tensor order parameters and is able to measure their symmetry and rank with minimal theoretical modeling. Here we propose to use laser-based nonlinear optical spectroscopy as a novel method to directly determine the symmetry and rank of tensor electronic order parameters. Three nonlinear optics based techniques will be simultaneously implemented to address a set of broad scientific questions about 5d and f-electron systems: 1) Nonlinear optical rotational anisotropy will be used to investigate the symmetry and rank of multipolar order parameters in materials that exhibit hidden order phase transitions. 2) Nonlinear optical microscopy and magneto-optical Kerr microscopy will be used to measure multipolar ordered domain structures and search for time-reversal broken superconducting ground states that emerge from multipolar ordered phases. 3) A combination of time-resolved linear and nonlinear optical pump-probe spectroscopy will be used to understand the dynamical interplay between the electronic structure, multipolar and lattice degrees of freedom across a photo-induced phase transition, with the goal of uncovering the microscopic mechanisms driving the thermal phase transitions.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 15, 2018
- Source ID
- W911NF1710204
Entities
People
- David Hsieh
Organizations
- Army Contracting Command
- California Institute of Technology
- United States Army