OHIO Researchers Manipulate Materials to Harness Novel Properties

Natalia Cortés [Photo by Jean Andrews/Ohio University]

Many researchers are currently interested in creating composite materials that are composed of two-dimensional atomic monolayers. A team of Ohio University researchers and their collaborators recently generated a theoretical model of one such system, describing the interactions between two drastically different materials. They described their work in an article published in Physical Review Letters in February.

The paper, titled “Tunable spin-polarized edge currents in proximitized transition metal dichalcogenides,” was led jointly by Universidad Técnica Federico Santa María doctoral student Natalia Cortés, and OHIO doctoral student Oscar Ávalos-Ovando, UTFSM professors Dr. Luis Rosales and Dr. Pedro Orellana, and OHIO Physics & Astronomy professor and NQPI member Dr. Sergio Ulloa. Cortés was previously a visiting student at OHIO, and she worked with Ulloa’s group, most recently during the spring of 2018.

In this paper, the authors focused on examining the properties of molybdenum ditelluride (MoTe₂) monolayers, deposited onto a ferromagnetic europium oxide (EuO) substrate. MoTe₂ is known to exhibit a direct bandgap and functions as a nonmagnetic conventional semiconductor.

The team was interested in modifying this property (when deposited on the ferromagnetic substrate) to explore the possibility of it on more efficient electronic devices. Their proposal consisted of depositing the material on top of a ferromagnetic substrate and studying the resulting properties of the combination.

“This combination provides a great example of the interesting ‘sharing’ of properties among materials by putting them in close proximity,” Cortés said.

Their results demonstrate that under appropriate conditions, the electronic states running along the sample edges form one-dimensional conducting channels with spin-polarized currents. By optimizing materials and conditions, this system could be applied to the creation of tunable spin device systems.

“This work is very exciting, as it can serve as a blueprint for experimentalists on which samples would be more promising to study,” Ávalos said. “We expect this will motivate further theoretical studies as well.”

Abstract: We explore proximity-induced ferromagnetism on transition metal dichalcogenides (TMDs), focusing on molybdenum ditelluride (MoTe2) ribbons with zigzag edges, deposited on ferromagnetic europium oxide (EuO). A tight-binding model incorporates exchange and Rashba fields induced by proximity to EuO or similar substrates. For in-gap Fermi levels, electronic modes in the nanoribbon are localized along the edges, acting as one-dimensional (1D) conducting channels with tunable spin-polarized currents. TMDs on magnetic substrates can become very useful in spintronics, providing versatile platforms to study proximity effects and electronic interactions in complex 1D systems.

Cortés was supported by CONICYT (Chile) and DGIIP USM. Rosales and Orellana were supported by Chilean FONDECYT and DGIIP USM. Avalos and Ulloa were supported by the National Science Foundation.