CIFAR’s program in Quantum Materials brings together some of the world’s foremost experts, both theoreticians and experimentalists, in condensed matter physics, quantum physics, materials engineering and related fields. Program fellows are making breakthrough discoveries in synthesizing and understanding the properties of new materials that promise to form the basis for emerging quantum technologies that could revolutionize communications, computers and other sectors.
One of the key techniques for materials characterization in quantum materials research is neutron scattering. Because neutrons are electrically neutral particles, they can penetrate deeply into materials and provide insight into their atomic structures. And because neutrons interact with magnetic fields, they are crucial tools for probing the often unusual magnetic properties of quantum materials that in turn affect their electronic behaviour, such as superconductivity (where electric current can pass without resistance). Several CIFAR fellows are top experts in neutron scattering, advancing its application as well as shaping the policies and infrastructure for the technique.
Broadly, there are two classes of neutron scattering techniques: neutron diffraction (or elastic neutron scattering), which is useful for determining magnetic spatial distribution; and inelastic neutron scattering, which allows for probing magnetic fluctuations, excitations and other dynamic properties. In combination, neutron scattering techniques are central to our understanding of the magnetic structure and behaviour of quantum materials.
Recent research involving neutron scattering conducted by fellows in CIFAR’s Quantum Materials program and their collaborators include:
- Investigations by Claudia Felser and colleagues on the magnetic structure of Heusler compounds, a large class of metal alloys that are multifunctional and highly tunable (with properties that can be adjusted, e.g., through temperature changes or chemical substitutions). These include IrMnGa, which exhibits spin glass behaviour (in which the magnetic orientation, or spin, of individual atoms is random, as opposed to being aligned as in “everyday” ferro-/ferrimagnets), and Mn1.4PtSn, a material hosting antiskyrmions (a kind of magnetic “vortices” which could form the basis of future devices for information storage and processing).
- Reports by Bruce Gaulin and colleagues on a variety of quantum materials, including TbInO3, a spin liquid (a crystalline compound in which the spin of component atoms, analogous to molecules in actual liquids, are disordered and dynamically fluctuating, and remain so down to very low temperatures); Yb2Ti2O7 and Ho2Ti2O7 (work done with Alannah Hallas), which are examples of spin ice (a particular class of spin liquids whose magnetic structure is analogous to the molecular structure of water ice); and La1.6−xNd0.4SrxCuO4, a family of high-temperature superconductors (including work done in collaboration with Louis Taillefer)
- Studies by Johnpierre Paglione and colleagues on (Li1−x−yFexMnyOD)FeSe, a compound that seems to demonstrate the coexistence of superconductivity and long-range magnetic order, and MoTe2, a candidate topological superconductor, both of which might be useful as a basis for “topological” quantum computers that are more robust to environmental perturbations; and Cu2OSeO3, a material hosting skyrmion magnetic vortices.
- Work by Kate Ross and colleagues on a variety of materials that help deepen our understanding of quantum magnetism, including Yb2Si2O7,Yb2Ge2O7, Er2Si2O7, K3Er(VO4)2, Fe3PO4O3, and HoAgGe. Ross is also a member of an advisory subcommittee that recently analyzed the scientific case for high-flux neutron sources for the United States Department of Energy.
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Gaudet J et al. 2018. Magnetoelastically induced vibronic bound state in the spin-ice pyrochlore Ho2Ti2O7. Phys. Rev. B 98:014419.
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Hester G et al. 2020. Evidence for a field-induced quantum phase transition in Ising-like D-Er2Si2O7. arXiv. Preprint.
Kroder J et al. 2019. Spin glass behavior in the disordered half-Heusler compound IrMnGa. Phys. Rev. B 99:174410.
Liu I-L et al. 2020. Quantum oscillations from networked topological interfaces in a Weyl semimetal. npj Quantum Mater. 5:62
Neves PM et al. 2020. Effect of chemical substitution on the skyrmion phase in Cu2OSeO3. Phys. Rev. B 102:134410.
Qianli M et al. 2020. Parallel spin stripes and their coexistence with superconducting ground states at optimal and high doping in La1.6−xNd0.4SrxCuO4. arXiv. Preprint.
Sarkis CL et al. 2020. Partial antiferromagnetic helical order in single-crystal Fe3PO4O3. Phys. Rev. B 101:184417.
Sarkis CL et al. 2020. Unravelling competing microscopic interactions at a phase boundary: A single-crystal study of the metastable antiferromagnetic pyrochlore Yb2Ge2O7. Phys. Rev. B 102:134418.
Vir P et al. 2019. Anisotropic topological Hall effect with real and momentum space Berry curvature in the antiskrymion-hosting Heusler compound Mn1.4PtSn. Phys. Rev. B. 99:140406(R).
Wilfong B et al. 2020. Long-range magnetic order in hydroxide-layer-doped (Li1−x−yFexMnyOD)FeSe. Phys. Rev. Mater. 4:034803.
Yahne DR et al. 2020. Pseudospin versus magnetic dipole moment ordering in the isosceles triangular lattice material K3Er(VO4)2. Phys. Rev. B 102:104423.
Zhao K et al. 2020. Realization of the kagome spin ice state in a frustrated intermetallic compound. Science 367:1218.