111,443 research outputs found
Vortex structures of rotating spin-orbit coupled Bose-Einstein condensates
We consider the quasi-2D two-component Bose-Einstein condensates with Rashba
spin-orbit (SO) coupling in a rotating trap. An external Zeeman term favoring
spin polarization along the radial direction is also considered, which has the
same form as the non-canonical part of the mechanical angular momentum. The
rotating condensate exhibits rich structures as varying the strengths of
trapping potential and interaction. With a strong trapping potential, the
condensate exhibits a half-quantum vortex-lattice configuration. Such a
configuration is driven to the normal one by introducing the external radial
Zeeman field. In the case of a weak trap potential, the condensate exhibits a
multi-domain pattern of plane-wave states under the external radial Zeeman
field.Comment: 8 pages, 7 figures, two figures are adde
Generating mid-IR octave-spanning supercontinua and few-cycle pulses with solitons in phase-mismatched quadratic nonlinear crystals
We discuss a novel method for generating octave-spanning supercontinua and
few-cycle pulses in the important mid-IR wavelength range. The technique relies
on strongly phase-mismatched cascaded second-harmonic generation (SHG) in
mid-IR nonlinear frequency conversion crystals. Importantly we here investigate
the so-called noncritical SHG case, where no phase matching can be achieved but
as a compensation the largest quadratic nonlinearities are exploited. A
self-defocusing temporal soliton can be excited if the cascading nonlinearity
is larger than the competing material self-focusing nonlinearity, and we define
a suitable figure of merit to screen a wide range of mid-IR dielectric and
semiconductor materials with large effective second-order nonlinearities
. The best candidates have simultaneously a large bandgap and a
large . We show selected realistic numerical examples using one of
the promising crystals: in one case soliton pulse compression from 50 fs to 15
fs (1.5 cycles) at 3.0\mic is achieved, and at the same time a 3-cycle
dispersive wave at 5.0\mic is formed that can be isolated using a long-pass
filter. In another example we show that extremely broadband supercontinua can
form spanning the near-IR to the end of the mid-IR (nearly 4 octaves).Comment: submitted to Optics Materials Express special issue on mid-IR
photonic
Giant Microwave Absorption in Metallic Grains: Relaxation Mechanism
We show that the low frequency microwave absorption of an ensemble of small
metallic grains at low temperatures is dominated by a mesoscopic relaxation
mechanism. Giant positive magnetoresistance and very strong temperature
dependence of the microwave conductivity is predicted.Comment: 4 pages, REVTeX3+mutlticol+epsf, one EPS figur
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