Condensed-Matter Physics & Materials Science Seminar

"Uncovering the interactions behind quantum phenomena"

Presented by Keith Taddei, Oak Ridge National Laboratory

Tuesday, December 18, 2018, 11:00 am — ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Quantum computing, spintronics and plasmonics are nascent fields with potential to radically change our technological landscape. Fundamental to advancing these technologies is a mastery of quantum materials such as superconductors, quantum-spin-liquids and multiferroics. Ideally, we would know exactly what interactions give rise to these phenomena and design materials suitable for applications however, such an understanding as of yet eludes us. Instead we are stuck digging around in the phase space of known quantum materials slowly uncovering pertinent details to their design, filling in pieces of our incomplete picture. In this presentation, I will discuss recent bits I have found in my use of neutron scattering to study quantum materials. Starting with a novel new family of quasi-one-dimensional (Q1D) superconductors (A1,2TM3As3 with A = alkali metal and TM = Cr, Mo) I will present findings of short-range structural order and a proximate magnetic instability which, due the radically different structure, allow for new insights to the pertinence to such orders to superconductivity. Importantly, in these materials the two orders break different symmetries and so their interactions with the superconducting order can be studied independently. Next, I will discuss an interesting yet neglected family of frustrated magnetic materials – the rare-earth pyrogermanates (REPG). We find the Er2Ge2O7 REPG to exhibit 'local-Ising' type magnetism in direct analogy to the spin-ice pyrochlores suggesting effects of local anisotropies and dipole interactions. Finally, I will present ongoing work investigating spin-driven polarization effects in the magnetically and structurally straightforward multiferroic BiCoO3. These results demonstrate the essential role of neutron and x-ray scattering techniques in studying these complex materials and the fruitful opportunities these systems present to advance our understanding of quantum materials.

Hosted by: Ian Robinson/Mark Dean

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