Driving Quantum Systems with Classical Fields

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

The ability to control the movement of electrons in semiconductor devices lies at the core of electronics, photonics, and phononics, which are basic-science fields that give rise to technological advances in energy, communication, sensing, information science, and security. Electrons are very small particles found in every atom, and they obey the laws of quantum mechanics, which makes it challenging to interact with them and control their motion in a highly predictable fashion. The central question behind this project is how one can use light and sound, both classical waves commonly encountered in daily lives, to excite or drive electrons in modern semiconductors devices. The size of these devices is a few nanometers, less than a thousandth of the thickness of a strand of human hair. Owing to the device small size and inescapable imperfections, it is much more challenging to understand how light and sound interact with electrons in devices than it is to answer the same question in much larger systems, such as bulk materials. However, the small device size may also lead to the emergence of striking new phenomena with great technological impact. To that end, state-of-the-art simulation software to analyze how electrons in nanoscale devices interact with classical light and sound will be developed during this project. Microscopic theory and accurate simulation tools benchmarked against experiment, such as those that will be developed during the course of this project, are invaluable for deepening the understanding of the world at the nanoscale and for predicting new phenomena and functionalities, all at a fraction of experimental cost. This project will benefit experimental groups in industry and academia by helping design new devices. The codes will be distributed as open source through GitHub to ensure widespread use. How can classical waves, electromagnetic or acoustic, be used to excite or drive quantum electronic systems in modern nanostructures? This question cuts through electronics, photonics, and phononics, and has technological repercussions ranging from energy to communication, sensing, information science, and security. The answer requires a deep understanding of the physical processes that characterize the interplay of charge with light and sound in nanomaterials and nanostructures, and the answer differs greatly from its analogue in bulk materials because the low dimensionality and small size of these systems result in their sensitivity to boundaries and edges, disorder, surrounding materials properties, and may also lead to the emergence of striking new plasmonic, polaronic, and excitonic phenomena. To that end, the objective in this project is to develop and deploy a comprehensive modeling approach, employing state-of-the-art simulation techniques for classical electromagnetic and elastic waves coupled with an efficient density-matrix technique for quantum electronic transport in order to understand and harness the interplay of light, sound, and charge at the nanoscale. The work will be organized into two thrusts, each centered on one type of the classical wave. Under Thrust 1: Light–matter interaction in nanomaterials, recent algorithmic advances in field-potential finite-difference time-domain computational electromagnetics will be integrated with those involving quantum transport simulation using the density matrix. In this new self-consistent solver, quantum transport and classical electrodynamics will be coupled self-consistently and at every time step. Under Thrust 2: Sound-matter interaction in nanomaterials, recent computational advances in the simulation of elastic-wave scattering in disordered media will be integrated with those involving quantum electron transport simulation using the density matrix. The new simulation will analyze systems in which surface acoustic waves drive quantum electronic transport in light-emitting nanostructures. The codes will be distributed as open source through GitHub, and will benefit experimentalists designing new devices. Undergraduate researchers will also take part in this project. 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.