8 research outputs found
Spin-dependent Scattering by a Potential Barrier on a Nanotube
The electron spin effects on the surface of a nanotube have been considered
through the spin-orbit interaction (SOI), arising from the electron confinement
on the surface of the nanotube. This is of the same nature as the
Rashba-Bychkov SOI at a semiconductor heterojunction. We estimate the effect of
disorder within a potential barrier on the transmission probability. Using a
continuum model, we obtained analytic expressions for the spin-split energy
bands for electrons on the surface of nanotubes in the presence of SOI. First
we calculate analytically the scattering amplitudes from a potential barrier
located around the axis of the nanotube into spin-dependent states. The effect
of disorder on the scattering process is included phenomenologically and
induces a reduction in the transition probability. We analyzed the relative
role of SOI and disorder on the transmission probability which depends on the
angular and linear momentum of the incoming particle, and its spin orientation.
We demonstrated that in the presence of disorder perfect transmission may not
be achieved for finite barrier heights.Comment: 16 pages, 15 figure
Quantitative conditional quantum erasure in two-atom resonance fluorescence
We present a conditional quantum eraser which erases the a priori knowledge
or the predictability of the path a photon takes in a Young-type double-slit
experiment with two fluorescent four-level atoms. This erasure violates a
recently derived erasure relation which must be satisfied for a conventional,
unconditional quantum eraser that aims to find an optimal sorting of the system
into subensembles with particularly large fringe visibilities. The conditional
quantum eraser employs an interaction-free, partial which-way measurement which
not only sorts the system into optimal subsystems with large visibility but
also selects the appropriate subsystem with the maximum possible visibility. We
explain how the erasure relation can be violated under these circumstances.Comment: Revtex4, 12pages, 4 eps figures, replaced with published version,
changes in Sec. 3, to appear in Physical Review
Anomalous Photon-Assisted Tunneling in Graphene
We investigated the Dirac electrons transmission through a potential barrier
in the presence of circularly polarized light. An anomalous photon-assisted
enhanced transmission is predicted and explained in a comparison with the
well-known Klein paradox. It is demonstrated that the perfect transmission for
nearly-head-on collision in an infinite graphene is suppressed in gapped
dressed states of electrons, which is further accompanied by shift of peaks as
a function of the incident angle away from the head-on collision. In addition,
the perfect transmission in the absence of potential barrier is partially
suppressed by a photon-induced gap in illuminated graphene. After the effect of
rough edges of the potential barrier or impurity scattering is included, the
perfect transmission with no potential barrier becomes completely suppressed
and the energy range for the photon-assisted perfect transmission is reduced at
the same time
Ultrafast optical detection of magnetic inhomogeneity in ferromagnetic La
Optically excited spin wave resonances in ferromagnetic La0.67Ca0.33MnO3 (LCMO) thin films are probed by subpicosecond Kerr-rotation experiments at 10 K. We identify an extra fundamental mode along with the confined spin wave modes, whose frequency and intensity are independent of film thickness, but depend strongly on the applied magnetic field. We attribute the origin of this mode to magnetic inhomogeneity at the FM ground state. Our results show that the picosecond time-resolved magneto-optical method is a powerful tool for detecting dynamic magnetic inhomogeneity in colossal magneto-resistance manganites