311 research outputs found
Superatom molecular orbitals: a new type of long-lived electronic states
We present ab initio calculations of the quasiparticle decay times in a
Buckminsterfullerene based on the many-body perturbation theory. A particularly
lucid representation arises when the broadening of the quasiparticle states is
plotted in the angular momentum and energy coordinates. In this representation
the main spectroscopic features of the fullerene consist of two occupied nearly
parabolic bands, and delocalized plane-wave-like unoccupied states with a few
long-lived electronic states (the superatom molecular orbitals, SAMOs) embedded
in the continuum of Fermi-liquid states. SAMOs have been recently uncovered
experimentally by M. Feng, J. Zhao, and H. Petek [Science 320, 359 (2008)]
using scanning tunneling spectroscopy. The present calculations offer an
explanation of their unusual stability and unveil their long-lived nature
making them good candidates for applications in the molecular electronics. From
the fundamental point of view these states illustrate a concept of the
Fock-space localization [B. L. Altshuler, Y. Gefen, A. Kamenev, and L. S.
Levitov, Phys. Rev. Lett. 78, 2803 (1997)] with properties drastically
different from the Fermi-liquid excitations
Light-induced valley currents and magnetization in graphene rings
We study the non-equilibrium dynamics in a mesoscopic graphene ring excited
by picoseconds shaped electromagnetic pulses. We predict an ultrafast buildup
of charge polarization, currents and orbital magnetization. Applying the light
pulses identified here, non-equilibrium valley currents are generated in a
graphene ring threaded by a stationary magnetic flux. We predict a finite
graphene ring magnetization even for a vanishing charge current; the
magnetization emerges due to the light-induced difference of the valley
populations.Comment: 4 pages, 2 figures, submitted to Phys. Rev.
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