Effects of topological edge states on the thermoelectric properties of Bi nanoribbons

Using first-principles calculations combined with Boltzmann transport theory, we investigate the effects of topological edge states on the thermoelectric properties of Bi nanoribbons. It is found that there is a competition between the edge and bulk contributions to the Seebeck coefficients. However, the electronic transport of the system is dominated by the edge states because of its much larger electrical conductivity. As a consequence, a room temperature value exceeding 3.0 could be achieved for both p- and n-type systems when the relaxation time ratio between the edge and the bulk states is tuned to be 1000. Our theoretical study suggests that the utilization of topological edge states might be a promising approach to cross the threshold of the industrial application of thermoelectricity

The Ultraviolet flash accompanying GRBs from neutron-rich internal shocks

In the neutron-rich internal shocks model for Gamma-ray Burts (GRBs), the Lorentz factors (LFs) of ions shells are variable, so are the LFs of accompanying neutron shells. For slow neutron shells with a typical LF tens, the typical beta-decay radius reads R_{\beta,s} several 10^{14} cm, which is much larger than the typical internal shocks radius 10^{13} cm, so their impact on the internal shocks may be unimportant. However, as GRBs last long enough (T_{90}>20(1+z) s), one earlier but slower ejected neutron shell will be swept successively by later ejected ion shells in the range 10^{13}-10^{15} cm, where slow neutrons have decayed significantly. We show in this work that ion shells interacting with the beta-decay products of slow neutron shells can power a ultraviolet (UV) flash bright to 12th magnitude during the prompt gamma-ray emission phase or slightly delayed, which can be detected by the upcoming Satellite SWIFT in the near future.Comment: 6 pages (2 eps figures), accepted for publication in ApJ

Tuning the carrier concentration to improve the thermoelectric performance of CuInTe2 compound

The electronic and transport properties of CuInTe2 chalcopyrite are investigated using density functional calculations combined with Boltzmann theory. The band gap predicted from hybrid functional is 0.92 eV, which agrees well with experimental data and leads to relatively larger Seebeck coefficient compared with those of narrow-gap thermoelectric materials. By fine tuning the carrier concentration, the electrical conductivity and power factor of the system can be significantly optimized. Together with the inherent low thermal conductivity, the ZT values of CuInTe2 compound can be enhanced to as high as 1.72 at 850 K, which is obviously larger than those measured experimentally and suggests there is still room to improve the thermoelectric performance of this chalcopyrite compound

Theory of control of spin/photon interface for quantum networks

A cavity coupling a charged nanodot and a fiber can act as a quantum interface, through which a stationary spin qubit and a flying photon qubit can be inter-converted via cavity-assisted Raman process. This Raman process can be controlled to generate or annihilate an arbitrarily shaped single-photon wavepacket by pulse-shaping the controlling laser field. This quantum interface forms the basis for many essential functions of a quantum network, including sending, receiving, transferring, swapping, and entangling qubits at distributed quantum nodes as well as a deterministic source and an efficient detector of a single photon wavepacket with arbitrarily specified shape and average photon number. Numerical study of noise effects on the operations shows high fidelity.Comment: 4 pages, 2 figure

Perturbation Theory for Plasmonic Modulation and Sensing

We develop a general perturbation theory to treat small parameter changes in dispersive plasmonic nanostructures and metamaterials. We specifically apply it to dielectric refractive index, and metallic plasma frequency modulation in metal- dielectric nanostructures. As a numerical demonstration, we verify the theory's accu- racy against direct calculations, for a system of plasmonic rods in air where the metal is defined by a two-pole fit of silver's dielectric function. We also discuss new optical behavior related to plasma frequency modulation in such systems. Our approach provides new physical insight for the design of plasmonic devices for biochemical sensing and optical modulation, and future active metamaterial applications.Comment: 17 pages, 6 figure