Transfer of orbital angular momentum of light to plasmonic excitations in metamaterials

The emergence of the vortex beam with orbital angular momentum (OAM) has provided intriguing possibilities to induce optical transitions beyond the framework of the electric dipole interaction. The uniqueness stems from the OAM transfer from light to material, as demonstrated in electronic transitions in atomic systems. In this study, we report on the OAM transfer to electrons in solid-state systems, which has been elusive to date. Using metamaterials (periodically textured metallic disks), we show that multipolar modes of the surface electromagnetic excitations (so-called spoof localized surface plasmons) are selectively induced by the terahertz vortex beam. Our results reveal selection rules governed by the conservation of the total angular momentum, which is confirmed by numerical simulations. The efficient transfer of light’s OAM to elementary excitations in solid-state systems at room temperature opens up new possibilities of OAM manipulation.

Influence of magnetic confinement on the yellow excitons in cuprous oxide subject to an electric field

We study the spectrum of the yellow exciton series in crossed electric and magnetic fields. The electric field, applied along the optical axis, tilts the Coulomb potential between electron and hole, so that at sufficiently high fields exciton dissociation becomes possible, roughly when the electric dipole interaction energy exceeds the binding energy of an exciton state with principal quantum number n . For an applied voltage of U = 20 V all excitons above n = 6 are dissociated. Additional application of a magnetic field normal to the optical axis introduces magnetic confinement, due to which above a threshold field strength around B = 2.5 T the exciton lines re-emerge. The complex dispersion with increasing fields suggests quantum chaotic behavior in this crossed field configuration, so that the search for exceptional points may be promising.

BROWNIAN MOTORS BASED ON ELECTRIC DIPOLE INTERACTION

Brownian motors based on electric dipoles interaction are studied. Directed motion is induced by the transitions of the electric dipoles potentials between two states. The stationary probability current of the Brownian motors is evaluated. The current is sensitive to temperature and the values of the transition rates between two states. There are optimal values of temperature and the transition rates for the current, and for a suitable choice of the transition rates the current can be reversed.

DYNAMICS OF A FERMI SYSTEM IN A BLACKBODY RADIATION FIELD

We derive a quantum master equation for a system of fermions coupled to the blackbody radiation field through the electric-dipole interaction. This equation is of Lindblad's form, with a hamiltonian part of the shell-model, and a dissipative art with microscopic coefficients, depending on physical constants, matrix elements, and parametrically only on temperature.