Emerging Polar Altermagnetic Metallic States in Epitaxially Strained RuO2 Film (14/08/25)
Speaker and Affliation:
Prof. Bharat Jalan
Department of Chemical Engineering and Materials Science, University of Minnesota, Twin Cities
When?
14th August, 2025 (Thursday), 4.00 PM (India Standard Time)
Where
KPA Auditorium, Dept. of Materials Engineering, IISc, Bangalore
Abstract:
RuO2, a rutile 4d-transition metal oxide, exhibits a unique crystal structure with both edge- and corner-sharing octahedra. This intrinsic anisotropy, when combined with strain engineering, provides a powerful avenue for tuning anisotropic electronic and optical properties. However, from a synthesis perspective, challenges such as variable Ru valence states, Ru/O stoichiometry control, anisotropic strain states, and structural defects can make it difficult to distinguish intrinsic properties from extrinsic effects in RuO2 thin films—a classic trick in the pursuit of novel functionalities in quantum materials.
In this talk, I will highlight our group’s efforts in overcoming these synthesis challenges while demonstrating metallicity in epitaxial RuO2 films down to the unit cell scale. Through a combination of advanced X-ray scattering, X-ray absorption spectroscopy, transmission electron microscopy, temperature-dependent transport, magneto-optical measurements, and density functional theory (DFT) calculations, we uncover robust magnetism in epitaxially strained RuO2, consistent with an altermagnetic metallic phase [1-3]. Additionally, we reveal a novel polar phase in strained films with significant implications for electrical transport—an unexpected treat in the realm of functional oxides. I will discuss these findings in detail, emphasizing their sensitivity to material defects and structure—key ingredients that are often overlooked but crucial in determining emergent quantum phenomena.
About the Speaker :
Professor Bharat Jalan, Shell Chair in the department of chemical engineering and materials science at the University of Minnesota. Prof. Jalan is a expert in materials science, renowned for pioneering work in oxide thin films, membranes, and heterostructures. He has developed novel MBE-based approaches enabling atomic-level growth of complex materials. Prof. Jalan also holds graduate faculty appointment in the Department of Physics, and the Department of Electrical and Computer Engineering at the University of Minnesota. He also serves as an Associate Editor of AAAS journal Science Advances. He has received numerous prestigious awards, including the Young Investigator MBE Award (2016), Air Force Office of Scientific Research Young Investigator Award (2016), Royal Society of Chemistry Emerging Young Investigator (2017), American Association for Crystal Growth Young Author Award (2017), AVS Paul Holloway Young Investigator Award (2017), Presidential Early Career Award for Scientists and Engineers (PECASE), AVS Peter Mark Memorial Award (2021), and recognition by the National Academy of Engineering as a highly accomplished early-career engineer (2022). He has also been honored with the international Schieber Prize (awarded to one worldwide every three years) by the International Organization of Crystal Growth (2023), AVS Fellow (2024), the VAIBHAV Fellowship by the Government of India (2024), and recently, as the JMR Distinguished Invited Speaker by the Materials Research Society at their 2024 spring meeting. Most recently, Jalan was presented with the University of Minnesota George W. Taylor Award for Distinguished Research. Jalan has (co)-authored more than 140 peer-reviewed publications and given more than 100 invited talks and colloquiums.