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Dirac metals
What to study?
For Prelims and mains: Dirac and semi- Dirac metals- features, applications and the recent breakthrough.
Context: Researchers from IIT Bombay have discovered special properties in a class of materials called “semi-Dirac metals”- 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.
What are Dirac metals?
The quality of conduction in normal metals like gold and silver depends on 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.
What is Unique about semi- Dirac metal?
- 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.
- 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. There are many known applications for transparent conducting films – the common example being touch screens used in mobiles.
Significance of the recent breakthrough:
The energy-momentum dispersion relation can be linear, leading to large velocities and vanishingly small effective masses. The velocities can be over a 100 times more than normal metals, thus increasing the mobility and currents that can be carried across devices made of these so-called Dirac materials.
In the semi-Dirac metals, these properties are direction dependent. The direction-dependence of the microscopical properties gives the material special optical properties.
Sources: the Hindu.
