Welcome!

Welcome to The Frustrated and Quantum Magnetism group and the Ross lab in the Department of Physics at Colorado State University. The group started in September 2015, and our lab is now fully operational. During our first year we’ve been busy with neutron scattering experiments, materials synthesis, and expanding our low temperature characterization tools.

We recently added a 3He / 4He dilution insert to our instrumentation, which allows us to take heat capacity measurements down to 50 mK and in magnetic fields up to 9T. This enables us to quickly search for phase transitions in strongly frustrated magnets, and to understand their low energy degrees of freedom.

Some pictures from our recent adventures:

: Dr. Nair at the Spallation Neutron Source

: Dr. Nair using the new dilution temperature insert

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 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).

Student Awards

Undergraduate researcher Tim Reeder won a prize for an excellent oral presentation that he gave at the Magnetics workshop held at CSU this fall.

Tim receiving a prize for an excellent oral presentation.

Undergraduate researcher Tyler Dodge has won prizes this year at two conferences (Front Range Advanced Magnetics Symposium 2016, and the APS Four Corners section meeting 2016) for his poster that described developing the Resonant Ultrasound Spectroscopy probe.

The award winning poster presenter, Tyler Dodge, and his poster on RUS

Recent results

Nanosized Helical Domains in Strongly frustrated Fe3PO4O3

Our first paper from an ongoing project started in the Neilson Lab was published in PRB as an editor’s suggestion. Fe3PO4O3 is a frustrated antiferromagnet with triangular motifs that decorate a simple rhombohedral lattice. The geometric frustration produces an anti-ferromagnetic helical magnetic structure with unusual needle-like domains. The domains are restricted to 70 Å in the hexagonal ab plane, while they are unrestricted along the c-axis, producing a very unusual neutron powder diffraction profile (see figure below) with broad and flat-topped magnetic peaks coexisting with a sharp magnetic peak. Due to the short correlation length of the domains in the ab plane, the material is expected to host many topological defects, i.e. domain walls or other defects, confined to be parallel to the c axis. Fe3PO4O3 could be of interest as a source of antiferromagnetic Skyrmions.

News

Oct. 2016: Tyler Dodge wins a best student poster prize at the APS Four Corners section meeting in Las Cruces, NM, for his work on Resonant Ultrasound Spectroscopy.
Oct. 2016: Kate wins the 2016 APS George E. Valley Jr. Prize
August 2016: Tyler Dodge wins a best student poster prize at FRAMS (Front Range Magnetics Symposium) for his work on Resonant Ultrasound Spectroscopy.
July 2016: Kate is appointed a CIFAR Global Scholar and joints the CIFAR Quantum Materials program for a 2 year term
May 2016: Cory Berg joins the group as an undergraduate researcher and Gavin Hester joins the group as a graduate researcher. Welcome Cory and Gavin!
Feb. 2016: Dr. Hari Nair joins the group. Welcome Hari!
Jan. 2016: Tim Reeder joins the group as an undergraduate researcher, and Jake Walker joins the group as a graduate researcher. Welcome Tim and Jake!
Jan. 2016: Optical Floating Zone Furnace installed in Ross lab
Nov. 2015: Kate was elected to the SNS-HFIR User Group Executive Committee (SHUG-EC) for a 3 year term.
Nov. 2015: Jesse attended his first neutron scattering experiment at the NIST Center for Neutron Research.
Oct. 2015: Jesse attended the APS Four Corners Meeting in Arizona and presented a poster about his ongoing research project.
July. 2015: Jesse and Kate attended the Kavli Institute for Theoretical Physics (KITP) meeting “Novel States in Spin–Orbit Coupled Quantum Matter”. Kate spoke about her recent work on Yb2Ti2O7.
June 2015: Kate spoke at the Gordon Research Conference on Neutron Scattering, held in Hong Kong.
March 2015: Kate gave an invited talk at the APS March Meeting in San Antonio, TX, on a new pyrochlore project: NaCaCo2F7
Jan. 2015: Kate taught at the Winter Theory School in Tallahassee, see slides from the school, including my lecture on “Experimental Pyrochlore Systems” here.
Nov. 2014: Kate received the Alice Wilson award from the Royal Society of Canada. From the RSC website: “The three Alice Wilson Awards are presented annually to women of outstanding academic qualifications … who are entering a career in scholarship or research at the postdoctoral level.”
Sept. 2014: Kate signed on as Assistant Professor in the Department of Physics at Colorado State University, beginning August 2015.
Sept. 2014: Kate took up an NSERC Post Doctoral Fellowship at Colorado State University, working in the Neilson Lab in the Department of Chemistry. She worked on crystal growth and synthesis, particularly on the material Fe3PO4O3.
Kate was awarded the 2014 Prize for Outstanding Student Research from the Neutron Scattering Society of America, and presented at the American Conference of Neutron Scattering (ACNS) in June, 2014.

Publication highlights

Nanosized Helical Domains in Strongly frustrated Fe3PO4O3. Phys. Rev. B 92, 134419 (2015)
Lightly stuffed pyrochlore structure of single-crystalline Yb2Ti2O7 grown by the optical floating zone technique. Phys. Rev. B 86, 174424 (2012)
Order by Quantum Disorder in Er₂Ti₂O₇. Phys. Rev. Lett. 109, 167201 (2012)
Quantum Excitations in Quantum Spin Ice. Phys. Rev. X 1, 021002 (2011).
Neutron Laue Diffraction Study on the Magnetic Phase Diagram of Multiferroic MnWO4 under Pulsed High Magnetic Fields. Phys. Rev. Lett., 106, 237202 (2011).

Some invited talks online

“”Quantum Spin Ice” Physics Determined from High Field Spin Wave Excitations in Yb2Ti2O7”: Exotic Phases of Frustrated Magnets, Kavli Institute for Theoretical Physics (KITP), Santa Barbara CA (October 2012)
“Effective Spin-1/2 Hamiltonians Determined for Er2Ti2O7 & Yb2Ti2O7 Through Inelastic Neutron Scattering”: 4-Corner Condensed Matter Symposium, Perimeter Institute, Waterloo ON (May 2012)

Welcome!

Publication highlights

Some invited talks online

See my personal website (coming soon!)