From UPSC perspective, the following things are important :
Prelims level : Dirac Metals
Mains level : Applications of Dirac materials
- Researchers from IIT Bombay have discovered special properties in a class of materials called “semi-Dirac metals” that have been recently talked about in the scientific literature.
What are Dirac metals?
- 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, for example, determine the conductivity and other such properties.
- This is also true of a semi-Dirac metal. In particular, the effective mass becomes zero for conduction along a special direction.
- Examples of semi-Dirac metals are systems such as TiO2/V2O3 nanostructures (Oxides of Titanium and Vanadium).
- Through calculations, the researchers have shown that such materials would be transparent to light of a given frequency and polarization 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.
- Optical conductivity is a measure of the opacity offered by the material to the passage of light through it.
- The research shows a very high optical conductivity of semi-Dirac materials for electromagnetic waves [light waves] of a specific frequency and specific polarization.
- The researchers show theoretically that semi-Dirac materials can display such thermoelectric properties.
- The study of thermoelectrics dwells on the heat-to electricity conversion efficiency, for which there has been recent and tremendous interest due to the advent of nanomaterials and quantum materials.
- Thermoelectricity is a clean energy technology that uses waste heat to produce electricity typically in low power applications.