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Biasing metal-semiconductor junctions involves applying a voltage across the junction. Specifically, the metal is connected to a voltage source, while the semiconductor is grounded. This technique is essential for controlling the direction and magnitude of current flow in electronic devices, including diodes, transistors, and photovoltaic cells.
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The contact of metal and semiconductor can lead to the formation of a junction with either Schottky or Ohmic behavior.
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The vacuum level denotes the energy threshold required for an electron to escape from a material surface. It is usually positioned above the conduction band of a semiconductor and acts as a benchmark for comparing electron energies within various materials.
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Weyl Semimetal Path to Valley Filtering in Graphene.

Ahmed M Khalifa1, Ribhu K Kaul1, Efrat Shimshoni2

  • 1Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506-0055, USA.

Physical Review Letters
|October 1, 2021
PubMed
Summary
This summary is machine-generated.

We developed a graphene-Weyl semimetal device that acts as a robust valley filter. This device controls electron flow in graphene valleys by utilizing bulk properties, not edge effects.

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Area of Science:

  • Condensed Matter Physics
  • Materials Science
  • Nanotechnology

Background:

  • Graphene exhibits unique electronic properties due to massless Dirac fermions.
  • Valleytronics aims to utilize electron valley degrees of freedom for information processing.
  • Existing valley filters often rely on complex edge structures or dimensions.

Purpose of the Study:

  • To propose and theoretically investigate a novel device for studying 2D to 3D massless Dirac fermion tunneling.
  • To demonstrate a robust and efficient valley filter based on graphene-Weyl semimetal heterostructures.
  • To explore a bulk-mediated mechanism for valley filtering in graphene.

Main Methods:

  • Theoretical modeling of a graphene-Weyl semimetal heterostructure.
  • Analysis of the reconstructed band structure and electron tunneling.
  • Simulation of electron transport and valley-dependent current flow.

Main Results:

  • The proposed device facilitates physical access to study tunneling from 2D to 3D massless Dirac fermions.
  • The reconstructed band structure of the coupled system enables robust valley filtering.
  • The Weyl semimetal selectively draws current from one graphene valley, allowing the other to pass.

Conclusions:

  • The graphene-Weyl semimetal device offers a novel platform for exploring Dirac fermion physics.
  • This device functions as an effective bulk-based valley filter, overcoming limitations of edge-dependent designs.
  • The findings pave the way for new strategies in valleytronics and electronic device applications.