Understanding the behavior of actinide materials is important for issues such as developing new technology and predicting the aging of our nation’s nuclear stockpile. These compounds have not been well studied and pose an additional challenge as they can display highly unusual behavior that deviates from patterns observed with elements from the rest of the periodic table. These anomalies can be traced to the nature of the 5f valence electrons, whose unique orbital shapes lead to electronic properties that vary between localized and itinerant behavior.
The alloy uranium ruthenium silicide (URu2Si2) displays a peculiar hidden order state, which has resisted explanation despite decades of experimental work. We sought to understand this state by applying large electric fields, an approach which has been useful for understanding other strongly-correlated materials. This method has been enabled by advances in modern device fabrication techniques, such as focused ion beam (FIB) lithography, which has made it possible to apply larger electric fields to a metal than previously achievable. By shedding light on the nature of this hidden order we expect to expand our understanding of 5f electron behavior and show that advances in modern device fabrication can lead to new experimental approaches that would otherwise not be possible.