33 research outputs found
Observation of charged excitons in hole-doped carbon nanotubes using photoluminescence and absorption spectroscopy
We report the first observation of trions (charged excitons), three-particle
bound states consisting of one electron and two holes, in hole-doped carbon
nanotubes at room temperature. When p-type dopants are added to carbon nanotube
solutions, the photoluminescence and absorption peaks of the trions appear far
below the E11 bright exciton peak, regardless of the dopant species. The
unexpectedly large energy separation between the bright excitons and the trions
is attributed to the strong electron-hole exchange interaction in carbon
nanotubes
Modulated vortex states in Rashba non-centrosymmetric superconductors
Vortex lattice structures to occur in Rashba non-centrosymmetric
superconductors under a magnetic field parallel to the basal plane are studied
by assuming a singlet Cooper pairing and taking account of both the
paramagnetic and orbital depairings. A vortex lattice of
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) type with modulation perpendicular to
the field is expected to occur in the limit of vanishing , where
is the spin-orbit coupling {\it normalized} by Fermi energy. As
increases, however, this state tends to be replaced by another
new vortex lattice with a modulation of the gap amplitude parallel to the
helical phase modulation induced by the absence of inversion symmetry.
Differences of the present results from those in the Pauli limit and a
correlation of a structural transition with the -curve are discussed
in relation to possible experimental realization.Comment: Final version accepted for publication in Phys.Rev.B (Rapid Commmun.
Raman study on the interlayer interactions and the band structure of bilayer graphene synthesized by alcohol chemical vapor deposition
We investigated the electronic band structure and interlayer interactions in graphene synthesized by alcohol-chemical vapor deposition (a-CVD) using microprobe Raman spectroscopy and tight-binding band-structure calculations. The number of graphene layers was determined from the spectrally integrated intensity ratios of the G phonon to 2D phonon peaks. We found that the value of the parameter determining interlayer interactions in a-CVD bilayer graphene was less than half that of exfoliated bilayer graphene. The weak interlayer interaction in a-CVD bilayer graphene was attributed to non-AB stacking order
Dynamics of light-induced anomalous Hall effect in the three-dimensional Dirac semimetal CdAs
We experimentally study the dynamical behavior of the light-induced anomalous
Hall effect in a three-dimensional Dirac semimetal, CdAs. An
ultrashort, circularly polarized, multi-terahertz pump pulse breaks the
time-reversal symmetry of a thin film sample. The resulting anomalous Hall
effect is clearly observed through the polarization rotation of a single-cycle
terahertz probe pulse. Comparing the experimental result with theory, we find
that the field-induced injection current dominates the anomalous Hall effect
during pump irradiation, while the Berry curvature of the Floquet-Weyl
semimetal state does not appreciably contribute. Remarkably, even after pump
irradiation, we observe an anomalous Hall effect that lasts for more than 10
ps. A model fit to the Hall conductivity spectrum reveals a relatively long
scattering time over 400 fs. This result shows that circularly polarized light
creates a polarization of the isospin degree of freedom in the Dirac semimetal,
which labels the crystallographic point group representation of the overlapping
Weyl semimetal bands. Our observation paves the way for conversion of a robust
isospin flow into an electric current at room temperature, being a new analogue
of the inverse spin Hall effect.Comment: 44 pages, 14 figure