Welcome to The Frustrated and Quantum Magnetism group and the Ross lab in the Department of Physics at Colorado State University.  

Important Update!

As of May 2022, the Quantum Magnetism group at CSU is no longer active.  Some of the Ph.D. candidates in the group are still active under new supervisors.  The PI, Kate Ross, has taken up a new position as part of her transition to a career in data science.  Thanks for reading!

Research Themes

Our research focuses on emergent phenomena in correlated electronic materials.  We focus on the synthesis (i.e. crystal growth) and characterization, via neutron scattering, of strongly interacting magnetic materials. A particularly exciting goal of this research is to realize what is known as the Quantum Spin Liquid state, where magnetic moments dance together in an entangled, correlated, but ultimately disordered and dynamic way.

Crystals with magnetic degrees of freedom offer enormous diversity of emergent phenomena arising from simple near-neighbor interactions in a vast group of magnetic ions (~1023 of them!). Dynamics ranging from “classical” spin waves that propagate a spin flip through an array of aligned moments, to emergent photon-like excitations that mimic electrodynamics, can be created, probed, and understood in this environment.

We use neutron scattering to directly probe the static and dynamic correlations in such materials. Neutron scattering has the advantage of providing directional and energy-resolved information, which can be successfully and simply compared with theory. Through collaborations with solid state chemists and condensed matter theorists, we strive to push the boundaries of magnetic solids towards strongly quantum entangled states.

New Capabilities Coming Online

Our group is developing a home-built resonant ultrasound spectroscopy (RUS) insert for the PPMS that will operate at fields up to H=9T and temperatures down to T=2K, with help from Prof. Leisure (CSU) and the Ultrasound group lead by Albert Migliori (Los Alamos National Lab).  We successfully acquired our first low temperature RUS spectrum in Jan 2018 and look forward to using this new tool.

Recent Adventures

Gavin and Danielle attended a polarized neutron spectroscopy workshop hosted by Oak Ridge National Lab.

Ross lab attended FRAMS 2019 where Kate gave an invited talk.

Colin and Steffen went to the NHMFL in Tallahassee, FL to run an experiment on the 30T magnet.

Danielle Yahne, Gavin Hester, and Colin Sarkis all presented their recent work at the 2019 Materials Research Society Spring meeting…

Student Awards

Danielle wins award for outstanding student presentation at APS 4CS meeting.

Gavin wins best poster award at the 5th Front Range Advanced Magnetics Symposium. Photo credit: Ron Goldfarb

Gavin’s talk, titled “A Novel Strongly Spin-Orbit Coupled Quantum Dimer Magnet: Yb2Si2O7”, wins a Best Presentation award at the Summer…

Danielle Yahne wins Best Poster award at the National High Magnetic Field Lab’s 2019 Theory Winter School in Tallahassee, FL….

Recent results

Partial antiferromagnetic helical order in single-crystal Fe3PO4O3

Recently published in Physical Review B: Magnetic frustration in Fe3PO4O3 produces an unusual magnetic state below Tn = 163K, where incommensurate antiferromagnetic order is restricted to nanosized needle-like domains. We report our single crystal neutron diffraction work, which show continuous rings of scattering in the ab-plane with a well-defined radius. Our analysis show Fe3PO4O3 does not choose a preferred ordering wavevector direction, despite having a fixed magnitude. We reproduce a quasi-degenerate manifold of ordering wavevectors using an antiferromagnetic Heisenberg model with nearest and second neighbor interactions. The state shows a stark similarity to the partially ordered phase of the skyrmion…

A Novel Strongly Spin-Orbit Coupled Quantum Dimer Magnet: Yb2Si2O7

Recently published in Physical Review Letters: The quantum dimer magnet (QDM) is the canonical example of “quantum magnetism”. We report our single crystal neutron diffraction, specific heat, and ultrasound velocity work on a new QDM in the strongly spin-orbit coupled, distorted honeycomb-lattice material Yb2Si2O7. These measurements reveal a gapped singlet zero field ground state with sharp, dispersive excitations. We find a field-induced magnetically ordered phase reminiscent of a BEC phase, with exceptionally low critical fields of Hc1 ~0.4 T and Hc2 ~1.4 T. These results raise the question of how anisotropy in strongly spin-orbit coupled materials modifies the field induced phases of…

Short-range order in the quantum XXZ honeycomb lattice material BaCo2(PO4)2

Recently published in Physical Review B: The magnetic honeycomb lattice with competing interactions can give rise to unconventional quantum phases.  We present observations of highly frustrated quasi two-dimensional (2D) magnetic correlations in the honeycomb lattice layers of the Seff = 1/2 compound BaCo2(PO4)2.  Specific heat lacks a sharp anomaly down to 2K although all spin entropy is recovered, indicating the absence of a transition to long range order in this material.  However, ac susceptibility shows that spins do not freeze into a spin-glass like state.    The spin correlations measured by neutron powder diffraction reveal short range quasi-2D order with…


Some invited talks online