Riku’s paper with Mike Ridley on charge pumping in ac-driven graphene nanoribbons has been published in Physical Review B. Congrats!
Popular summary: Typically, electronic current flowing through a conductor needs a net voltage to be applied across the conductor. However, applying an alternating voltage, which is zero on average, may induce a direct current. This mechanism is known in the engineering literature as AC-DC conversion or rectification. Here we investigated this mechanism in a quantum transport setup consisting of graphene nanoribbons, and derived some general “rules of thumb” for quantum pumping.
Our preprint “Light-enhanced electron-phonon coupling from nonlinear electron-phonon coupling” is available on arXiv. In this work, it is shown how one can amplify electron-lattice coupling by using lasers that are tuned to a phonon, that is coupled quadratically to the electrons of the material. Such enhanced electron-lattice coupling can lead to the formation of polarons – electrons coupled to a “cloud” of lattice distortion – or even make the system superconducting. It has recently been debated how possible light-induced superconductivity in carbon football molecular crystal (“fullerenes”) may come about, and nonlinear electron-phonon coupling might play an important role. Similarly, more direct signatures of light-enhanced electron-lattice coupling have been observed in metallic bilayers of the carbon flatland material graphene. Now experiments have to be performed to check the hypothesis of our theory paper.
In a new theory published on arXiv today we show how a laser beam can exert control in a system with competing superconducting and charge orders. The underlying mechanism with a striking resonance for photon frequencies near the gap edge may even be used to understand light-induced superconductivity. The above figure illustrates how a symmetry between the competing orders allows for low-energy excitations corresponding to a rotation of a composite order parameter towards charge order (CDW, left) or towards superconductivity (SC, right).