MAE's Nabavi, Zhao Advanced Material System Development For Next-Generation Thermal Management, On-Chip Photonics

A new paper published in Nature Communications by researchers in the Mechanical and Aerospace Engineering Department at the Cullen College of Engineering demonstrates a powerful new approach to controlling electromagnetic waves — achieving strong asymmetric infrared optical responses in a solid-state material at room temperature without the need for an externally applied bias.

The advance could open new pathways toward compact technologies for quantum hardware, on-chip photonics, thermal management and high-efficiency energy conversion.

The first author is Bardia Nabavi, a Ph.D. candidate advised by Bo Zhao, Kalsi Assistant Professor in the department. Zhao is the corresponding author of the paper, “Observing strong optical nonreciprocity from magnetically doped Dirac semimetals,” published in Nature Communications.

Sina Jafari Ghalekohneh, a recent Ph.D. graduate, also contributed to the research. Project collaborators include Hervé Ness and Dimitar Pashov in the Department of Physics at King’s College London, as well as Mark van Schilfgaarde, Ian Leahy, Anthony Rice, Andrew Norman and Kirstin Alberi from the National Laboratory of the Rockies (NLR) in Golden, Colorado.

The experimental effort relied on a custom instrument built by Nabavi and Ghalekohneh. Zhao described it as “a custom high-temperature emission measurement setup mated to an infrared spectrometer, assembled in our lab.” NLR grew the samples, while King’s College London and NLR contributed electronic-structure theory, with UH leading the project.

According to the paper, in most conventional optical materials, electromagnetic waves act symmetrically: their fundamental response remains symmetric when the direction of propagation is reversed. Breaking this symmetry is essential for technologies such as optical isolators and circulators, which control the direction in that light and electromagnetic wave can travel. This behavior can also enable directional radiative heat transfer, providing a route toward thermal–diode–like behavior. However, conventional approaches often require external magnetic field with bulky components, creating a major obstacle to miniaturizing such technologies for photonics and energy applications.

In this work, the researchers introduced manganese into cadmium arsenide, an exotic topological material known as a Dirac semimetal. The magnetic moments introduced by manganese break the time-reversal symmetry. This transformation produces an exceptionally strong intrinsic magnetic field up to hundreds of Tesla even without an externally applied bias.

“The result is a one-way infrared response roughly 100 times stronger than conventional doped semiconductors and 1,000 times stronger than ferromagnetic metals, at room temperature, with no external magnet,” Zhao said. “We tune it with doping and flip it with a handheld magnet.”

The ability to engineer such strong symmetry-breaking directly into a material could provide a new platform for compact optical and thermal components, including isolators, circulators, rectifiers and other devices designed to control the directional flow of electromagnetic energy. Potential applications extend from on–chip photonics and quantum technologies to thermal management, energy harvesting and directional radiative heat transfer.

“Quantum hardware and high-efficiency energy conversion are two of the areas drawing the heaviest federal and industrial investment in the world right now, and Houston is the city that has to lead the energy side of that transition,” Zhao said.

Nabavi joined UH in 2024 to pursue his Ph.D. in Mechanical and Aerospace Engineering. His research focuses on developing material platforms for one-way electromagnetic-wave propagation. He has received graduate-student fellowships and best presentation award from MRS and ASME in connection with this research.

“My inspiration has always been to make the people of my country, Iran, proud, and through my research, I try to contribute toward that goal to be their voice,” Nabavi said. “This work demonstrates a path toward future quantum technologies, with potential implications for hardware and data-center cooling. I am grateful for this achievement and dedicate this work to all my loved ones and my people, including those who are no longer with us.”

Zhao joined the Cullen College faculty in Fall 2021. He has been a prolific researcher in that time frame, earning a National Science Foundation CAREER award in 2025 and receiving funding for multiple proposals related to thermal emission and solar energy harvesting. His Thermal PhotoniX (TPX) Lab engages in the theoretical and experimental understanding of photonic transport processes for thermal management, energy conversion and information processing.