Temperature and electric field control of the bandgap in electrotoroidic nanocomposites by large-scale ab initio methods

Abstract

An effective Hamiltonian scheme combined with a GPU implementation of the linear-scaling three-dimensional fragment (LS3DF) method is used to compute electronic properties of two topological objects in a nanocomposite: an electrical vortex coexisting with spontaneous electrical polarization over a wide temperature range and an electrical skyrmion over a range of applied electric fields. Temperature control of the vortex provides substantially larger range of control of bandgap and band alignment than field control of the skyrmion. Using temperature and electric fields to manipulate polarization and bond angle distortion in different component materials provides a handle for bandgap engineering in such nanostructures.

KEYWORDS:

• Electrical vortex
• skyrmion
• bandgap engineering
• polarization rotation
• linear scaling

Acknowledgment

We acknowledge some helpful discussions with Charles Paillard.

Funding

The LS3DF + PEscan calculations were performed using resources of the Oak Ridge Leadership Computing Facility (OLCF) with processor time allocated under the ASCR Leadership Computing Challenge (ALCC) Project and Innovative and Novel Computational Impact on Theory and Experiment (INCITE) Project NTI009.. All effective Hamiltonian calculations were completed using resources of the Arkansas High Performance Computing Center (AHPCC). R.W. was financially supported by the U.S. Department of Energy, Office of Science Graduate Student Research (SCGSR) program, administered by the Oak Ridge Institute for Science and Education (ORISE) for the DOE. Y.N. and L.B. acknowledge support of the ARO grant W911NF-16-1-0227. S.P. acknowledges financial support of the DARPA grant HR0011-15-2-0038 (under the MATRIX program). Y.N., S.P., and L.B. also thank the support of the DARPA grant HR0011727183-D18AP00010 (under the TEE program).