Tunable Fano-Kondo resonance in side-coupled double quantum dot system

We study the interference between the Fano and Kondo effects in a side-coupled double-quantum- dot system where one of the quantum dots couples to conduction electron bath while the other dot only side-couples to the first dot via antiferromagnetic (AF) spin exchange coupling. We apply both the perturbative renormalization group (RG) and numerical renormalization group (NRG) approaches to study the effect of AF coupling on the Fano lineshape in the conduction leads. With particle-hole symmetry, the AF exchange coupling competes with the Kondo effect and leads to a local spin-singlet ground state for arbitrary small coupling, so called "two-stage Kondo effect". As a result, via NRG we find the spectral properties of the Fano lineshape in the tunneling density of states (TDOS) of conduction electron leads shows double dip-peak features at the energy scale around the Kondo temperature and the one much below it, corresponding to the two-stage Kondo effect; it also shows an universal scaling behavior at very low energies. We find the qualitative agreement between the NRG and the perturbative RG approach. Relevance of our work to the experiments is discussed.Comment: 7 pages, 7 figure

Properties of Microlensing Central Perturbations by Planets in Binary Stellar Systems under the Strong Finite-Source Effect

We investigate high-magnification events caused by planets in wide binary stellar systems under the strong finite-source effect, where the planet orbits one of the companions. From this, we find that the pattern of central perturbations in triple lens systems commonly appears as a combination of individual characteristic patterns of planetary and binary lens systems in a certain range where the sizes of the caustics induced by a planet and a binary companion are comparable, and the range changes with the mass ratio of the planet to the planet-hosting star. Specially, we find that because of this central perturbation pattern, the characteristic feature of high-magnification events caused by the triple lens systems appears in the residual from the single-lensing light curve despite the strong finite-source effect, and it is discriminated from those of the planetary and binary lensing events and thus can be used for the identification of the existence of both planet and binary companion. This characteristic feature is a simultaneous appearance of two features. First, double negative-spike and single positive-spike features caused by the binary companion appear together in the residual, where the double negative spike occurs at both moments when the source enters and exits the caustic center and the single positive spike occurs at the moment just before the source enters into or just after the source exits from the caustic center. Second, the magnification excess before or after the single positive-spike feature is positive due to the planet, and the positive excess has a remarkable increasing or decreasing pattern depending on the source trajectory.Comment: 12 pages, 3 figures, accepted for publication in Ap

The use of COD as an indicator for evaluation of pretreatment of nitrocellulose with acid hydrolysis

Nitrocellulose is a toxic waste by definition. It is widely used in military and commercial industries. Nitrocellulose fines escaped from the manufacture\u27s process has created problems in receiving water. However, little information is available for the treatment of nitrocellulose. Nitrocellulose is difficult to treat by microorganisms without any pretreatment. Therefore, the main objective of this study is to use acid hydrolysis to break down this material before biological treatment, and find the optimal operation conditions in this process. In this work, the results indicate that percentage of nitrocellulose decomposing in hydrolysis depends on types of acid, acid concentration, reaction temperature, and reaction time. For single stage hydrolysis system, the maximum decomposition occurred when acid was 18 N and 36 N H2SO4 at any reaction temperature or 38 % HCI at high temperature. In two stage hydrolysis system, it was found that the second stage reaction had significant effect on the yield of glucose. However, the rate and amount of nitrocellulose dissolved was smaller than that of the first stage system

6.4 GHz Acoustic Sensor for In-situ Monitoring of AFM Tip Wear

This paper demonstrates an acoustic sensor that can resolve atomic force microscopy (AFM) tip blunting with a frequency sensitivity of 0.007%. The AFM tip is fabricated on a thin film piezoelectric aluminum nitride (AlN) membrane that is excited as a film bulk acoustic resonator (FBAR). We demonstrate that cutting 0.98 μm off of the tip apex results in a resonance frequency change of 0.4MHz at 6.387GHz. This work demonstrates the potential for in-situ monitoring of AFM tip wear

Properties of the Planetary Caustic Perturbation

Just two of 10 extrasolar planets found by microlensing have been detected by the planetary caustic despite the higher probability of planet detection relative to the central caustic which has been responsible for four extrasolar planet detections. This is because the perturbations induced by the planetary caustic are unpredictable, thus making it difficult to carry out strategic observations. However, if future high-cadence monitoring surveys are conducted, the majority of planetary caustic events including the events by free-floating planets and wide-separation planets would be detected. Hence, understanding the planetary caustic perturbations becomes important. In this paper, we investigate in detail the pattern of the planetary caustic perturbations. From this study, we find three properties of the planetary caustic perturbations. First, planetary systems with the same star-planet separation (s) basically produce perturbations of constant strength regardless of the planet/star mass ratio (q), but the duration of each perturbation scales with sqrt{q}. Second, close planetary systems with the same separation produce essentially the same negative perturbations between two triangular-shaped caustics regardless of q, but the duration of the perturbations scales with sqrt{q}. Third, the positive perturbations for planetary systems with the same mass ratio become stronger as the caustic shrinks with the increasing |log s|, while the negative perturbations become weaker. We estimate the degeneracy in the determination of q that occurs in planetary caustic events. From this, we find that the mass ratio can be more precisely determined as q increases and |log s| decreases. We also find that the degeneracy range of events for which the source star passes close to the planetary caustic is usually very narrow, and thus it would not significantly affect the determination of q.Comment: 5 pages, 3 figures, 2 tables, accepted in MNRA

Distinguishing central perturbations by binary stellar and planetary systems under the moderately strong finite-source effect

We investigate high-magnification events caused by wide binary stellar and planetary systems under the moderately strong finite-source effect where the diameter of the source star is comparable with the caustics induced by a binary companion and a planet. From this investigation, we find that a characteristic feature in the central perturbations induced by the binary systems commonly appears in a constant range where the size of the caustic induced by the binary companion is between 1.5 and 1.9 times of the diameter of the source, whereas in the central perturbations induced by the planetary systems the feature commonly appears in a range where the ratio of the size of the caustic induced by the planet to the source diameter changes with the planet/primary mass ratio. High-magnification events caused by the binary and planetary systems with the characteristic feature produce a distinctive short-duration bump in the residuals from the single-lensing light curve, where the bump occurs near the time of peak magnification of the events. Because of a well-known planet/binary degeneracy, we compare binary- and planetary-lensing events with the short-duration bump in the residuals. As a result, we find the features of the binary-lensing events that are discriminated from the planetary-lensing events despite the moderately strong finite-source effect and thus can be used to immediately distinguish between the binary and planetary companions. We also find the feature that appears only in binary-lensing events with a very low mass ratio or planetary-lensing events. This implies that the lens systems with the feature have a very low mass binary companion (such as a brown dwarf) or a planet.Comment: 18 pages, 7 figures, accepted by Ap

A Suspended Nanogap Formed by Field-Induced Atomically Sharp Tips

A sub-nanometer scale suspended gap (nanogap) defined by electric field-induced atomically sharp metallic tips is presented. A strong local electric field (\u3e109 V=m) across micro/nanomachined tips facing each other causes the metal ion migration in the form of dendrite-like growth at the cathode. The nanogap is fully isolated from the substrate eliminating growth mechanisms that involve substrate interactions. The proposed mechanism of ion transportation is verified using real-time imaging of the metal ion transportation using an in situ biasing in transmission electron microscope (TEM). The configuration of the micro/nanomachined suspended tips allows nanostructure growth of a wide variety of materials including metals, metal-oxides, and polymers. VC 2012 American Institute of Physics

A Planetary lensing feature in caustic-crossing high-magnification microlensing events

Current microlensing follow-up observations focus on high-magnification events because of the high efficiency of planet detection. However, central perturbations of high-magnification events caused by a planet can also be produced by a very close or a very wide binary companion, and the two kinds of central perturbations are not generally distinguished without time consuming detailed modeling (a planet-binary degeneracy). Hence, it is important to resolve the planet-binary degeneracy that occurs in high-magnification events. In this paper, we investigate caustic-crossing high-magnification events caused by a planet and a wide binary companion. From this study, we find that because of the different magnification excess patterns inside the central caustics induced by the planet and the binary companion, the light curves of the caustic-crossing planetary-lensing events exhibit a feature that is discriminated from those of the caustic-crossing binary-lensing events, and the feature can be used to immediately distinguish between the planetary and binary companions. The planetary-lensing feature appears in the interpeak region between the two peaks of the caustic-crossings. The structure of the interpeak region for the planetary-lensing events is smooth and convex or boxy, whereas the structure for the binary-lensing events is smooth and concave. We also investigate the effect of a finite background source star on the planetary-lensing feature in the caustic-crossing high-magnification events. From this, we find that the convex-shaped interpeak structure appears in a certain range that changes with the mass ratio of the planet to the planet-hosting star.Comment: 14 pages, 4 figures. Accepted for publication in Ap