New polaritons multi-valley model may help valleytronics research

Researchers from the Institute for Basic Science (IBS) in Korea published a new paper that models the behavior of polaritons in microcavities, nanostructures made of a semiconductor material sandwiched between special mirrors (Bragg mirrors).

Plot of polaritons' energy dispersion vs momentum in a semiconductor microcavit

The new research helps to understand polaritons, microcavities and have potential implications for future valleytronics devices - such taht use valleys of polaritons. The IBS researchers have generated a theoretical model for valley polarization.

Researchers demonstrate the nematic quantum hill effect on crystal bismuth

Researchers from Princeton University and the University of Texas-Austin have demonstrated that electrons on a crystal bismuth exhibit the Nematic Quantum Hall Liquid effect at very low temperatures.

Nematic quantum Hall liquid on the surface of bismuth

This is the first time that a quantum fluid of electrons is visualized. As valleytronics aims to exploit the energy level of electrons in relation to their momentum, this is an important step toward realizing this technology.

Researchers use bi-layer graphene to create a device that control electron flow based on the valley degree of freedom

Researchers from Penn State University demonstrated a new device, based on bi-layer graphene, that provides an experimental proof of the ability to control electron-flow by the valley degree of freedom. This is still an early-stage development, but could be seen as an important step towards valleytronics.

Bi-layer graphene based valleytronics experiment (Penn State)

The device is built from a bi-layer graphene, and gates above and below the graphene layer. Adding an electric field perpendicular to the plane opens a bandgap in the bi-layer graphene, and a physical gap (70 nanometer in height) is left, in which one-dimensional metallic states (wires) exists. These states act as valleytronics valves.

Researchers suggest a way to pump carriers valley-selectively

Researchers at the University of Geneva proposed a novel approach to optically ‘pump’ carriers valley-selectively using a high-purity bismuth crystal.

UNIGE bismuth optically pump carriers valley selectively

In bismuth there are three valleys and the electrons orbit in magnetic field that are strongly elongated along one direction due the interaction with the atomic lattice. Each valley has its own direction - which means that the direction can be used to discriminate between the valleys.

Researchers demonstrate a valleytronics device based on TMDC

Researchers at Berkeley Lab have experimentally demonstrated the ability to electrically generate and control valley electrons in transition metal dichalcogenide (TMDC, a 2D semiconductor) .

Berkeley lab TMDC valleytronic schema

The researchers say that this is the first demonstration of electrical excitation and control of valley electrons. TDMCs are considered to be more mature (closer to production) than any other semiconductors that exhibit valleytronic properties.

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