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Current Affairs

Quantum materials for clean energy

Date: 01 November 2019 Tags: Energy

Issue

Researchers from IIT Bombay have discovered special properties in a class of materials called “semi-Dirac metals” which can be utilised for producing clean energy.

 

Background

A quantum material is a label that has come to signify the area of condensed-matter physics formerly known as strongly correlated electronic systems.

Although the field is broad, a unifying theme is the discovery and investigation of materials whose electronic properties cannot be understood with concepts from contemporary condensed-matter textbooks.

 

Details

  • Results in the study show a very high optical conductivity of semi-Dirac materials for electromagnetic waves [light waves] of a specific frequency and specific polarisation.

  • Normal metals like gold and silver are good conductors of electricity. A key aspect that decides the quality of conduction is the way energy depends on the momentum of electrons.

  • Dirac metals differ from normal metals in that the energy depends linearly on the momentum. This difference is responsible for their unique properties.

  • Semi-Dirac metals behave like Dirac metals in one direction and like normal metals in the perpendicular directions (since their microscopic structure is different along the two directions).

  • Within any material, charge carriers, such as electrons, acquire an effective mass which is different from their bare mass depending on the nature of the material. The effective mass and the number of states available for the electron to occupy when it is excited by an electric field, determine the conductivity and other such properties.

  • With the advent of man-made 2D materials, such properties have become quite tailor able in what comprises the active field of quantum materials. The velocities can be over a100 times more than normal metals, thus increasing the mobility and currents that can be carried across devices made of these so-called Dirac materials.

  • The semi-dirac materials are capable of producing Thermoelectricity. Thermoelectricity is a clean energy technology that uses waste heat to produce electricity typically in low power applications.

Semi-Dirac

  • Semi-Dirac metals are systems such as TiO2/V2O3 nanostructures. Through calculations, the researchers have shown that such materials would be transparent to light of a given frequency and polarisation when it is incident along a particular direction.

  • The material would be opaque to the same light when it falls on it from a different direction. There are many known applications for transparent conducting films, the common example being touch screens used in mobiles.