4,633 research outputs found
Tuning a magnetic Feshbach resonance with spatially modulated laser light
We theoretically investigate the control of a magnetic Feshbach resonance
using a bound-to-bound molecular transition driven by spatially modulated laser
light. Due to the spatially periodic coupling between the ground and excited
molecular states, there exists a band structure of bound states, which can
uniquely be characterized by some extra bumps in radio-frequency spectroscopy.
With the increasing of coupling strength, the series of bound states will cross
zero energy and directly result in a number of scattering resonances, whose
position and width can be conveniently tuned by the coupling strength of the
laser light and the applied magnetic field (i.e., the detuning of the ground
molecular state). In the presence of the modulated laser light, universal
two-body bound states near zero-energy threshold still exist. However, compared
with the case without modulation, the regime for such universal states is
usually small. An unified formula which embodies the influence of the modulated
coupling on the resonance width is given. The spatially modulated coupling also
implies a local spatially varying interaction between atoms. Our work proposes
a practical way of optically controlling interatomic interactions with high
spatial resolution and negligible atomic loss.Comment: 9pages, 5figur
Ballistic Thermal Rectification in Asymmetric Three-Terminal Mesoscopic Dielectric Systems
By coupling the asymmetric three-terminal mesoscopic dielectric system with a
temperature probe, at low temperature, the ballistic heat flux flow through the
other two asymmetric terminals in the nonlinear response regime is studied
based on the Landauer formulation of transport theory. The thermal
rectification is attained at the quantum regime. It is a purely quantum effect
and is determined by the dependence of the ratio
on , the phonon's frequency.
Where and are respectively the
transmission coefficients from two asymmetric terminals to the temperature
probe, which are determined by the inelastic scattering of ballistic phonons in
the temperature probe. Our results are confirmed by extensive numerical
simulations.Comment: 10 pages, 4 figure
Secrecy sum rate maximization in non-orthogonal multiple access
Non-orthogonal multiple access (NOMA) has been recognized as a promising technique for providing high data rates in 5G systems. This letter is to study physical layer security in a single-input single-output (SISO) NOMA system consisting of a transmitter, multiple legitimate users and an eavesdropper. The aim of this letter is to maximize the secrecy sum rate (SSR) of the NOMA system subject to the users' quality of service (QoS) requirements. We firstly identify the feasible region of the transmit power for satisfying all users' QoS requirements. Then we derive the closed-form expression of an optimal power allocation policy that maximizes the SSR. Numerical results are provided to show a significant SSR improvement by NOMA compared with conventional orthogonal multiple access (OMA)
- …