Electron density of states in terahertz driven two-dimensional electron gases

In this paper, a detailed theoretical study of the density of states (DOS) is presented for free electrons in terahertz (THz) driven two-dimensional electron gases (2DEGs). Using the Green's function approach and including the electron-photon interaction exactly, we have derived the electronic DOS in a THz driven 2DEG. The results obtained show that: (1) in the presence of intense THz electromagnetic radiations, the maximum DOS in the system will be shifted to the high-energy regime; (2) a stronger effect of the radiation on electron DOS and Fermi energy can be observed at relatively low-frequency and/or high-intensity radiations where the energy shift induced by the radiation field plays an important role in determining the DOS and the Fermi energy; (3) the processes of the multiphoton absorption and emission will lead to a small increase in DOS; and (4) as a consequence of (1) and (2), an intense THz radiation will drive electrons in a 2DEG to occupy higher electronic subbands.