Palestrante: Dr. Narcizo M. DE S. Neto
Título: Condensed matter at Sirius, the new Brazilian synchrotron source
Data: 16/08/2022 às 16:30h – Adicione ao calendário
Assistir e Link para participante

Resumo: Sirius, the new Brazilian synchrotron light source at Campinas-SP, one of the brightest and first fourth-generation machines in the world, is opening up a plethora of opportunities to study areas such as condensed matter physics with conditions yet nonexistent. Today we have several challenges to provide a complete understanding of physical mechanisms in condensed matter phenomena, as superconductivity for example. That in part can be tackled by employing experimental x-ray techniques, such as XRD, XMCD, RIXS and ARPES, that will be available at Sirius to access, for example, how electronic states are affected depending on multiple factors (temperature, interface, crystallinity, applied fields and pressure, etc). This information could in principle be used to test, validate or propose new physics theories in ways not yet imagined. In this talk I will give an overview of several possibilities for condensed matter and materials research with synchrotron techniques at diverse conditions and sensitivities. The state-of-the-art light source will also be overviewed.


Palestrante: Prof. Dr. Marcos Gonçalves de Menezes (UFRJ)
Título: Franckeite as an Exfoliable Naturally Occurring Topological Insulator
Data: 23/08/2022 – Adicione ao calendário
Assistir e Link para participante

Resumo: Franckeite is a natural superlattice composed of two alternating layers of different composition which has shown potential for optoelectronic applications. In part, the interest in franckeite lies in its layered nature which makes it easy to exfoliate into very thin heterostructures. Not surprisingly, its chemical composition and lattice structure are so complex that franckeite has escaped screening protocols and high-throughput searches of materials with nontrivial topological properties. On the basis of density functional theory calculations, we predict a quantum phase transition originating from stoichiometric changes in one of franckeite composing layers (the quasihexagonal one). While for large concentrations of Sb franckeite is a sequence of type-II semiconductor heterojunctions, for a large concentration of Sn, these turn into type-III, much like InAs/GaSb artificial heterojunctions, and franckeite becomes a strong topological insulator. Transmission electron microscopy observations confirm that such a phase transition may actually occur in nature.