Quadron-polariton: a new semiconductor quasiparticle

Contrary to real particles whose basic properties (mass, charge, spin) are stable and may be determined once and forever, the properties of quasiparticles propagating in crystals can be tuned by a proper design of crystal structures and different external factors (heating, illumination of the crystal by light, application of electric or magnetic fields). This allows for creation of new kinds of quasiparticles by relatively simple means. This project proposes a new quasiparticle which has never been observed nor theoretically described before. We call it quadron-polariton. Quadron because it is composed by four elementary quasiparticles (three electrons and one hole) and polariton because it is created by light passing its polarization to the crystal. The quadron-polaritons are expected to have truly remarkable properties. They carry a negative charge equal to two electron charges. They have an effective mass which is approximately 10000 times lighter than the free electron mass. They are spatially extended over a few wave-lengths of light. Finally, they have an integer spin and obey the statistics of Bose-Einstein therefore. That is why, we expect that quadron-polaritons should be able to form a superfluid, i.e. roughly speaking, to unify their energies and velocities. Theoretically, because of the very light mass of quadron-polaritons, their condensation may happen even at room temperature in specially designed crystal structures. The superfluid of quadron-polaritons would be charged, that is why its creation is expected by us to lead to the phenomenon of superconductivity (circulation of current without any applied voltage). Observation of light-induced superconductivity would be an extraordinary discovery also having a considerable economic effect. We are going to pave the way towards this observation by complex theoretical and experimental studies of quadron-polaritons in ultrathin artificial crystal structures.