Gathering Data On Dirac Electrons

Dirac electrons can be simply described as electrons that follow the Dirac equation. In recent years more and more materials have been discovered in which electrons act as Dirac electrons. The basic difference can be seen by the fact that the kinetic energy of a particle is:                    E_{\text{k}}={\frac {p^{2}}{2m}}            while the energy of a photon is    E = pc  \,.

This means that the energy of particles with mass increases according to the momentum squared while the energy of massless particles increases linearly with momentum. Generally the band structure of materials is parabolic in the sense the electrons have maxima and minima of energy. But in some materials even the electrons have a linear dispersion of energy in relation to their momentum and in this way they act like photons. This doesn’t mean the electrons are now massless and they still can’t move at the speed of light but it does mean the electrons gain a lot of the other properties associated with photons such as a homogeneous velocity.

Investigating materials that have this effect can be done by mixing it with other quantum effects. Magnetism, for instance, has a very dramatic effect on the energy levels in Dirac materials. Both SrMnBi2 (strontium, manganese, bismuth) and CaMnBi2 (cadmium, manganese, bismuth) are Dirac materials and display magnetic properties and so were the focus of one of the most recent research papers. By using some advanced Raman scattering both materials estimations of the exchange energy (the energy released when two electrons, or any identical particle really, exchange position to become more stable) between equal orbitals but were calculated. It was also shown that magnetic fields caused the band structure of the materials to widen, a fact which explained some previously observed electrical properties. This study provides quantitative data which can be used in order to explain and predict the nature of Dirac materials and hopefully find unique applications for them in new and advanced electronics.


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