A team of physicists from the University of Ottawa have developed a new theoretical model that shines new light on how scientists understand the way lasers interact with dense matter, such as solids and liquids. This could unlock advances in ultrafast physics and next-generation technology.
Conducted under the supervision of Professor Thomas Brabec, the uOttawa physics team tackled a long-standing limitation in the widely-used “relaxation time approximation” model. This method predicts how laser driven electrons lose phase coherence. It has been the basic workhorse in attosecond science for years, despite the model not always being accurate.
A New Model for Extreme Conditions
“While it works well for dilute gases, we found that for denser materials and stronger laser fields, it overestimated how quickly electrons lose coherence,”, says Dr. Lu Wang, a Postdoctoral Fellow in the Department of Physics at the University of Ottawa and corresponding author of the study.
That’s a significant problem, given that ionization - the process by which electrons are knocked free from atoms- underpins many key technologies, from high-harmonic generation and electron acceleration to laser machining. Inaccurate models risk holding back progress in attosecond science, which explores events happening on the fastest timescales known to physics.
To address this, the researchers developed a “heat bath” model that captures the complexity of many-body interactions without overwhelming computational resources. Their new approach, called the Strong Field Spin-Boson (SFSB) model, revealed surprising results. Depending on the nature of the heat bath and temperature, ionization rates can skyrocket or be dramatically suppressed by several orders of magnitude.
Breaking the Limits of Traditional Physics
“This framework lets us bring many-body physics into the study of intense laser fields with minimal complexity,” explains Dr. Wang. “It could open up new avenues for discovering phenomena in strong field and attosecond physics that were previously hidden.”
The implications are far-reaching. The SFSB model can be applied immediately to challenges in nonlinear optics and the development of tabletop X-ray sources. It also offers a pathway to more precise control over light-matter interactions at the fastest timescales science can probe.
This project drew on expertise from the National Research Council of Canada, the University of Arizona, and UAE University. The team’s findings mark a significant step forward in the understanding of electrons in extreme environments.
The study, titled “Strong field physics in open quantum systems”, was published in IOP SCIENCE.