University of Connecticut

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Condensed Matter Physics Seminar

Tuesday, May 1, 2018
2:00pm – 3:00pm

Storrs Campus
Physics Building, P121

Dr. Ryan E. Baumbach, National High Magnetic Field Laboratory, Florida State University

Probing hidden order in URu2Si2: Si → P chemical substitution as a new knob to turn

URu2Si2 persists as a confounding puzzle in condensed matter physics mainly because it hosts an unidentified ordered state ("hidden order") below T0 ≈ 17.6 K and unconventional superconductivity below Tc ≈ 1.5 K. These phenomena occur within a strongly hybridized f-electron lattice that is reminiscent of what is seen for structurally and chemically related systems, many of which which conform to the ubiquitous quantum critical point paradigm. For those materials, superconductivity is associated with quantum fluctuations that emerge as an ordered state (usually magnetic) is suppressed towards zero temperature. This is clearly not the case for URu2Si2, and various measurements show that (1) hidden order does not have an intrinsic magnetic moment and (2) the superconductivity is completely enclosed by hidden order. A multitude of theories have been proposed to describe this behavior, but no consensus has been reached regarding their success. In order to elucidate this situation we have tuned URu2Si2 using electronic shell filling (Si → P), where rich phenomena are observed. Importantly, both hidden order and superconductivity are replaced by heavy fermion metallic behavior without any ordering for chemical substitutions of less than 2%. Even as the ground state abruptly changes, the high temperature strongly hybridized correlated electron lattice remains close to its virgin state. In order to further expose this evolution, we have carried out Shubnikov de Haas quantum oscillation measurements probing the Fermi surface and charge carrier effective masses in the x region where hidden order is destroyed. I will discuss how these results may provide a window into the hidden order puzzle and their implications for different models of URu2Si2.


Prof. J. Hancock

Physics Department (primary)

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