CM Seminar - Unconventional magnetism and quantum disorder in NaYbO2

07 Nov2019

Speaker: Stephen Wilson

Time: November 7, 2019 :: 2:00PM - 3:00PM


Brimacombe 311

Abstract:  The triangular lattice of antiferromagetically coupled spins has long served as the paradigm of geometric magnetic frustration. An accompanying host of unconventional magnetic ground states predicted in this setting, and, as the spins on the lattice approach the quantum limit, these range from predictions of quantum spin liquid phases to unusual regimes of fluctuation-driven order.  While ideal manifestations of materials with perfect equilateral triangles of S=1/2 ions are rare, the field has recently enjoyed a resurgence due to the development of new classes of materials possessing nearly ideal triangular lattices decorated instead with rare-earth ions.  At sufficiently low temperatures for Kramers ions such as Yb, it then becomes possible to explore the magnetism of an ideal Jeff=1/2 triangular lattice of moments.  Here I will present some of our recent work exploring the magnetic ground state of one such compound, NaYbO2, which forms a model triangular lattice of frustrated Yb3+ ions within a chemically ideal framework.  Despite evidence for substantial magnetic exchange for a Yb-based compound, no signatures of magnetic order are detected down to 50 mK.  Instead a quantum disordered state manifests which can be driven via the application of a magnetic field into a fluctuation-driven “up-up-down” plateau phase prior to reaching the fully field-polarized state.  The implications of our findings regarding the formation of intrinsic quantum disorder in NaYbO2 will be discussed.

Biography:  Prof. Stephen Wilson serves as an Associate Professor and the Associate Chair of the Materials Department at the University of California, Santa Barbara.  After obtaining his Ph.D. from the Physics Department at University of Tennessee in 2007, he worked at Lawrence Berkeley National Laboratory as a postdoc prior to joining the faculty of the Physics Department at Boston College in 2010 as an Assistant Professor.  After moving to UC Santa Barbara in 2014, he has since been appointed an Associate Director of the California Nanosystems Institute and also serves as a co-director of the recently established NSF Quantum Foundry on campus.  His research group focuses on the exploration of novel electronic states and phase behaviors in a variety of materials ranging from quantum magnets to strongly spin-orbit coupled correlated electron systems.