A new type of composite alloys hetero-crystals and relevant phenomena

When
Location
PAN 110
Who
Boqun Song, Iowa State University
Abstract
The speaker will present a concept, namely hetero-crystal materials, associated with new dimensions for tuning material properties. Distinct from surface-growing hetero-structures, the hetero-crystals are defined as bulk materials, which consist of layered skeleton structures and A-B stacking layers of hetero-cations. Varying the cation species leads to significant changes of symmetry and other parameters, granting an exceptional chance to manipulate spin textures, superconductivity, half- collapsing phases, etc. The recently discovered 1144-phase is chosen as a case study to demonstrate its stability, unique features and intimate links with different research interests.



The second part of the talk is about a phenomenon taking place in such systems (1144-phase KCaFe4As4): mutual induction of Superconductivity (SC) and anti-ferromagnetism (AF). The discovering line is similar to E-F fields. Faraday discovers the law of mutual induction for E-B fields; Maxwell equations reveal the Lorentz symmetry hidden underneath. In a similar vein, our work demonstrates that SC and SVC orders could induce each other (two-way) in generic situations (pure-SC, pure-AF, coexisting). The equation of motion reveals the symmetry imposed on them. That is to say, SC-AF could belong to the components of a single unified order parameter. Noteworthy, cuprate superconductors manifest similar features in previous studies, and this discovery may shed light on broader range of questions.
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