CAREER: Chiral Phenomena of Excited States in Spintronics

Auburn University, Auburn AL

Investigators

Abstract

Nontechnical Abstract: Chirality is a ubiquitous phenomenon in nature, ranging from elementary particles to chemistry and biomolecules. Most studied chiral phenomena rely on a static view of chirality, that is, whether an object can be superimposed on its mirror image. In fact, the concept of chirality can be extended to moving objects: rattleback, for example, is a spinning top that only rotates in a preferred direction. In condensed matter systems, dynamic chirality can lead to a variety of interesting phenomena and applications. Here, the research team focuses on the chiral interactions between structural, electronic, magnetic dynamics in atomically thin van der Waals materials. The research project brings together advanced spectroscopy and modeling techniques to investigate the optical and transport properties emerged from chiral interactions. These properties hold the promise of producing circularly polarized light and realizing unidirectional dynamics of electrons, which can be implemented into novel opto-electronic device applications. The research aspects of this CAREER plan are integrated with extensive opportunities for education and outreach activities. Graduate and undergraduate students are not only trained in materials science, nanofabrication, and laser physics in the principal investigator’s lab, but also involved in spectroscopy experiments using national lab facilities. Also, the research team actively engage the K-12 students and general public to convey the concept of chirality and the beauty of symmetry by developing new STEM demos and games. Technical Abstract: In condensed matter systems, the concept of dynamic chirality expands the scope of spintronics with various intriguing properties. In this process, chirality plays a critical role in the energy and angular momentum transfer among different degrees of freedom. The objective of this project is to study novel magneto-optical effects and nonreciprocal transport properties that emerge from chiral interactions between magnetic, phononic, and photonic excitations in two-dimensional materials and van der Waals heterostructures. The research team are seeking to address several most current and relevant scientific problems in spintronics: 1) How to coherently excite chiral phonons and lift chiral phonon degeneracy in an achiral material? 2) How does chirality mediate the magnon-phonon coupling in the two-dimensional limit? and 3) How to implement chiral interactions in a phonon diode device for nonreciprocal signal operation? A battery of state-of-the-art experimental techniques at the home institution and the national laboratories such as nonlinear optics, helicity-resolved Raman scattering, and ferromagnetic resonance spectroscopy are employed to carry out the research tasks. This research project shed light on the emergent chiral phenomena in a broader class of materials and advance spintronics towards the interdisciplinary regime with quantum information science. This project is jointly funded by the Condensed Matter Physics Program (CMP) in the Division of Materials Research and by the Established Program to Stimulate Competitive Research (EPSCoR). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.