CAREER: Engineering topological order in tunable artificial ruthenate heterostructures

Non-Technical Abstract: Topological phases in condensed matter systems have emerged as a fascinating new paradigm in the past few decades. Such phases are of great interest due to their fantastic potential for numerous quantum information science applications, including as building blocks of quantum computers. Complex oxide materials have been predicted to host such phases, in some cases at elevated temperatures suitable for broad practical use. In this project, the research team aims to develop the synthesis and characterization of such materials using several approaches to maximize the probability for discovery of unique topological phases. Success of this research will establish a new class of topological materials and determine their potential for applications. This project also addresses the current need for increased educational activity for both topological physics and materials science. For the former, the principal investigator is developing two new courses focused on topological physics for both undergraduate and graduate students. For the latter, an annual week-long summer camp for middle-school students is being held in the research laboratory. Technical Abstract: Complex oxides host a variety of fascinating properties with many possible applications in quantum information science. Unfortunately, many of these efforts are stymied by the difficulty of the required synthesis and characterization techniques. In particular, strontium ruthenate has received heavy scrutiny in recent decades due to its unconventional superconductivity and ferromagnetic instability. The controversial superconductivity was until very recently believed to be odd parity with potential for hosting Majorana fermions. Furthermore, theoretical calculations also predict topological phases in ruthenates when confined along atypical crystallographic orientations. In this project, the research team is investigating both behaviors by synthesis and band structure characterization of geometrically engineered ruthenate heterostructures. Innovative pulsed laser deposition techniques are adapted to stabilize the materials in the required orientations despite the polarity mismatch between layers. Surface preservation and cleaning procedures in combination with state-of-the-art characterization techniques such as angle-resolved photoemission spectroscopy and cross-sectional scanning tunneling microscopy are implemented to study these materials. Realization of topological phases in geometrically engineered oxides would provide key insight into their properties and facilitate their utilization in quantum information devices. 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.