Engineering topics
Bauer, E. D.
Publications and source records attributed to Bauer, E. D..
Kondo quasiparticle dynamics observed by resonant inelastic x-ray scattering
Effective models focused on pertinent low-energy degrees of freedom have substantially contributed to our qualitative understanding of quantum materials. An iconic example, the Kondo model, was key to demonstrating that the rich phase diagrams of correlated metals originate from the interplay of localized and itinerant electrons. Modern electronic structure calculations suggest that to achieve quantitative material-specific models, accurate consideration of the crystal field and spin-orbit interactions is imperative. This poses the question of how local high-energy degrees of freedom become incorporated into a collective electronic state. Here, we use resonant inelastic x-ray scattering (RIXS) on CePd 3 to clarify the fate of all relevant energy scales. We find that even spin-orbit excited states acquire pronounced momentum-dependence at low temperature—the telltale sign of hybridization with the underlying metallic state. Our results demonstrate how localized electronic degrees of freedom endow correlated metals with new properties, which is critical for a microscopic understanding of superconducting, electronic nematic, and topological states.
Colossal anomalous Nernst effect in a correlated noncentrosymmetric kagome ferromagnet
Uranium-based ferromagnet demonstrates notable ability to convert heat to electricity.
Local characterization of a heavy-fermion superconductor via sub-Kelvin magnetic force microscopy
Using magnetic force microscopy operating at sub-Kelvin temperatures, we characterize the heavy fermion superconductor CeCoIn5. We pinpoint the absolute London penetration depth of λ(0)=435 ± 20 nm and report its temperature dependence, which is closely linked to the symmetry of the superconducting gap. In addition, we directly measure the pinning force of individual Abrikosov vortices and estimate the critical current density of jc=9×104 A/cm2. In contrast to the related, well-established tunnel diode oscillator technique, our method is capable of resolving inhomogeneities locally on the micrometer scale at ultra-low temperature.
Evidence for a pressure-induced antiferromagnetic quantum critical point in intermediate-valence UTe 2
Multicomponent superconductivity in intermediate-valence UTe 2 emerges from an antiferromagnetic quantum critical point.
Topological energy barrier for skyrmion lattice formation in MnSi
We report the direct measurement of the topological skyrmion energy barrier through a hysteresis of the skyrmion lattice in the chiral magnet MnSi. Measurements were made using small-angle neutron scattering with a custom-built resistive coil to allow for high-precision minor hysteresis loops. The experimental data were analyzed using an adapted Preisach model to quantify the energy barrier for skyrmion formation and corroborated by the minimum-energy path analysis based on atomistic spin simulations. Here, we reveal that the skyrmion lattice in MnSi forms from the conical phase progressively in small domains, each of which consisting of hundreds of skyrmions, and with an activation barrier of several eV.
Large tunable anomalous Hall effect in the kagome antiferromagnet U 3 Ru 4 Al 12
The Berry curvature in magnetic systems is attracting interest due to the potential tunability of topological features via the magnetic structure. f electrons, with their large spin-orbit coupling, abundance of noncollinear magnetic structures, and high electronic tunability, are attractive candidates to search for tunable topological properties. In this study, we measure anomalous Hall effect (AHE) in the distorted kagome heavy fermion antiferromagnet U 3 Ru 4 Al 12 . Furthermore, a large intrinsic AHE in high fields reveals the presence of a large Berry curvature. Moreover, the fields required to obtain the large Berry curvature are significantly different between B ∥ a and B ∥ a * , providing a mechanism to control the topological response in this system. Theoretical calculations illustrate that this sensitivity may be due to the heavy fermion character of the electronic structure. These results shed light on the Berry curvature of a strongly correlated band structure in magnetically frustrated heavy fermion materials but also emphasize 5 f electrons as an ideal playground for studying field-tuned topological states.