Charge density waves and superconductivity in the electron-hole gas: An intuitive physical explanation for nonexperts and experimentalists

In two recent papers by the author, the electron-positive fermion (hole) gas is simply modeled as two independent fermion gases interacting via the coulomb interaction. Known electron gas results are scaled to the mass of the positive fermion. Divergences in the linear response functions indicate instabilities. The divergence at q=0 occurs when the bulk modulus becomes zero. At mass ratios > 4.97 and certain densities, another divergence occurs at finite q. This new result is a charge density wave (CDW) enabled by the additional electronic screening of the holes. The large number of equations and algebra in these papers may obscure the simple physics which is emphasized in this presentation.

The effective electron-electron interaction has an attractive term due to the holes that contains the CDW divergence and leads to superconductivity. In the normal state, electron-hole scattering is the source of the T² electrical resistivity that also becomes large near the CDW.

If the electron-hole gas were to exist near the mass ratio and density of the CDW, it would have a large normal state resistivity with a T² temperature dependence and a high superconducting transition temperature.