Add to Calendar 2026-03-26T10:00:00 2026-03-26T11:00:00 Real-Space Superconductivity: Schafroth, Bipolarons, Cuprates Event Information: The idea that superconductivity might arise from the condensation of real-space electron pairs was proposed by Swiss physicist Robert Schafroth several years before the development of BCS theory. Although this concept is now known as Bose-Einstein-condensation superconductivity, Schafroth’s contributions are largely forgotten. In this talk, I will briefly review Schafroth’s work and his complex relationships with John Bardeen and Leon Cooper. I will then describe a version of real-space superconductivity involving phonon bipolarons as normal-state charge carriers. I argue that anisotropic bipolarons account for many of the properties of the copper-oxide superconductors discovered in 1986. I will discuss how a deeper understanding of bipolarons might help raise the critical temperature beyond the current record of 133 K.     Event Location: BRIM 311

Add to Calendar 2026-04-02T10:00:00 2026-04-02T11:00:00 High rank multipole order: feeling the strain Event Information: Interactions can lead to a wide variety of ordered states in materials. Phase transitions in which local atomic states develop spontaneous high rank multipole order provides a particularly rich arena for new insights. A key element in the study of such systems is the ability to couple to the associated order parameter. I will describe how one can couple to a variety of different multipolar states, motivating new methodologies to measure a fundamental thermodynamic material property, the multipole susceptibility. One can also identify effective transverse fields, which, when applied inside the ordered state, induce quantum fluctuations and can drive a multipolar quantum phase transition. I will explain the very special roles that strain can play for each of the cases, and will outline new experimental approaches in which the materials 'feel the strain' in different ways. Even while we manipulate the crystal lattice to tune electronic order, hyperfine interactions are not always completely innocent. Along the way I will introduce the special case of an electro-nuclear quantum phase transition.  Event Location: BRIM 311