Armando Pezo

TITLE:

Spin- and orbital-charge conversion at the surface states of Bi1-xSbx Topological insulators

ABSTRACT:

Topological insulators are quantum materials characterized by Time-reversal protected surface states (TSS) which make them appealing candidates for the design of next generation of highly efficient spintronic devices. The very recent demonstration of large transient spin-charge conversion (SCC) and subsequent powerful THz emission from Co|Bi1-xSbx bilayers clearly demonstrate such potentiality and feasibility for the near future [1-3]. Amongst the exotic properties appearing in and at the surface of such quantum materials, spin-momentum locking (SML) remains as a key ingredient to effectively convert the spin degree of freedom into a charge or a voltage signal. In that sense, in this work we will provide clear theoretical and numerical insights implemented by multiorbital and multi-layered tight-binding methods (TB). These developments clarify our recent experimental results obtained by THz-TDS spectroscopy techniques in the time domain [2]; and allows us to disentangle the various magnetic SCC contributions. Taking advantage of their spin-momentum locking property, we also postulate the occurrence of Orbital-to-charge conversion (OCC) taking place also in these aforementioned experiments at equal footing to SCC. By extending the spin-to-charge conversion theory, we postulate the emergence of its orbital counterpart, namely the Orbital-charge conversion (OCC), covering different contributions in terms of the orbital degree of freedom. Our results unveil the interest and prospects for the use of specific materials as source of both spin and orbital current (as Ni); and we may anticipate the advantage of using lighter elements with the restricting requirement of large SOC would be avoided in the latter case.

BIO:

Armando Pezo is a theoretical physicist specializing in condensed matter theory, particularly in spintronics. He completed his Ph.D. at the University of ABC and he is currently affiliated to the Albert Fert Laboratory – Paris-Saclay University. His research involves first-principle calculations to investigate the electronic and magnetic properties of quantum materials. By integrating these simulations with linear response theory, he can access transport properties that are essential for understanding, modeling, and engineering electronic devices for future applications.