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We observed an isostructural phase transition in the solid nitrogen λ-N2 at approximately 50 GPa accompanied by anomalies in lattice parameters, atomic volume and Raman vibron modes. The anomalies are ascribed to a slight reorientation of the nitrogen molecules, which does not seem to affect the monoclinic symmetry (space group P21/c). Our ab initio calculations further confirm the phenomena, and suggest an optimized structure for the λ-N2 phase. In addition, a new high-pressure amorphous phase of η′-N2 was also discovered by a detailed investigation of the pressure-temperature phase diagram of nitrogen with the aim of probing the phase stability of λ-N2. Our result may provide helpful information about the crystallographic nature of dissociation transitions in diatomic molecular crystals (H2, O2, N2, etc).

We periodically modulate the lattice trapping potential of a $^{87}$Sr optical clock to Floquet engineer the clock transition. In the context of atomic gases in lattices, Floquet engineering has been used to shape the dispersion and topology of Bloch quasi-energy bands. Differently from these previous works manipulating the external (spatial) quasi-energies, we target the internal atomic degrees of freedom. We shape Floquet spin quasi-energies and measure their resonance profiles with Rabi spectroscopy. We provide the spectroscopic sensitivity of each band by measuring the Fisher information and show that this is not depleted by the Floquet dynamical modulation. The demonstration that the internal degrees of freedom can be selectively engineered by manipulating the external degrees of freedom inaugurates a novel device with potential applications in metrology, sensing and quantum simulations., 6 pages, 4 figures, including supplementary material, comments are welcome and more information at http://cqutp.org/users/xfzhang/

There is a considerable amount of work that shows the biomagnetism of organic components without ferromagnetic components at the molecular level, but it is of great challenge to cover the giant gap of biomagnetism between their experimental and theoretical results. Here we show that the diamagnetism of aromatic peptides is greatly enhanced for about 11 times by self-assembling, reaching two orders of magnitude higher than the mass susceptibility of pure water. The self-assembly of aromatic rings in the peptide molecules plays the key role in such a strong diamagnetism.

We report a continuous-wave end-pumped Nd:YVO4 zigzag slab laser with multilayer amplified spontaneous emission (ASE) absorbing coatings. The coatings are deposited on the slab faces. A five-layer structure consists of SiO2-Ti-SiO2-Ti-Au, and the thicknesses are 2520 nm, 10 nm, 160 nm, 24 nm and 200 nm, respectively. The designed coatings show good performance for the ASE control in the experimental tests. A stable-unstable hybrid laser oscillator along orthogonal directions in the slab aperture is further configured, achieving the 117W output at a pump of 328 W. The beam quality factors M2 in the unstable direction and stable direction are 1.57 and 1.66, respectively.

The spin-polarized photocurrent is used to study the in-plane electric field dependent spin transport in undoped InGaAs/AlGaAs multiple quantum wells. In the temperature range of 77–297 K, the spin-polarized photocurrent shows an anisotropic spin transport under different oriented in-plane electric fields. We ascribe this characteristic to two dominant mechanisms: the hot phonon effect and the Rashba spin-orbit effect which is influenced by the in-plane electric fields with different orientations. The formulas are proposed to fit our experiments, suggesting a guide of potential applications and devices.

We demonstrate a high power, high brightness, slab amplifier based on face-pumped Nd:YAG slab gain modules, having a high efficient hybrid cooling system of the conduction cooling and forced convection cooling. Using a single gain module, a laser output power up to 4.5 kW with a remarkable optical-optical conversion efficiency of 51% is realized, indicating an excellent lasing performance of the Nd:YAG slab module. The amplifier operates at a repetition rate of 700 Hz and delivers a maximum average output power exceeding 10.5 kW with pulse duration of 150 μs. A good beam quality factor is measured to be β = 1.9. To the best of our knowledge, this is the highest brightness for a 10 kW level Nd:YAG slab amplifier.

Surface leakage currents of AlGaN/GaN high electron mobility transistors are investigated by utilizing a circular double-gate structure to eliminate the influence of mesa leakage current. Different mechanisms are found under various passivation conditions. The mechanism of the surface leakage current with Al2O3 passivation follows the two-dimensional variable range hopping model, while the mechanism of the surface leakage current with SiN passivation follows the Frenkel-Poole trap assisted emission. Two trap levels are found in the trap-assisted emission. One trap level has a barrier height of 0.22 eV for the high electric field, and the other trap level has a barrier height of 0.12 eV for the low electric field.

Nanocrystalline La0.5Na0.5TiO3 powders were prepared by the stearic acid-gel method, and the grain sizes could be controlled by varying annealing temperatures. The sizes were determined to be from 14 to 50 nm using Scherrer's formula. A very strong blue-light emission band around 480 nm was clearly observed in the nano-sized La0.5Na0.5TiO3 with a grain size of 14 nm at room temperature. Also, nano-size effects on the luminescence properties were investigated. These results could be explained with the aid of a self-trapped exciton model.

We report the ultra-high efficiency transport of cold 87Rb atoms using a moving magnetic quadrupole potential generated by three overlapping pairs of fixed coils. The transfer efficiency is better than 97%, which is the highest ever reported to our knowledge. The temperature increase due to heating is less than 10 when the initial cloud temperature is 110 μK. Our setup is similar to the magnetic transferring belt design [Phys. Rev. A 63 (2001) 031401(R)], although it is simpler because the push coil is not required. We use it to transport atoms away from a magneto-optical trap to very close to the wall of the glass cell, facilitating future experiments employing three-dimensional optical lattices, high resolution in-situ imaging, and magnetic Feshbach resonances.

In this paper, we re-analyze the $1^{-+}$ and $0^{++}$ light hybrids from QCD sum rules with a Monte-Carlo based uncertainty analysis. With $30\%$ uncertainties in the accepted central values for QCD condensates and other input parameters, we obtain a prediction on $1^{-+}$ hybrid mass of $1.71 \pm 0.22$\,GeV, which covers the mass of $\pi_1(1600)$. However, the $0^{++}$ hybrid mass prediction is more than 4\,GeV, which is far away from any known $a_0$ meson. We also study the correlations between the input and output parameters of QCD sum rules.

Considering the inclusive process, we study the doubly heavy baryon Ξcc (Ξbb) production through e+e− annihilation. Both the diquark QQ in color sextet and triplet are discussed. The results show that the contributions from these two color states play equally important roles. At the Z0 pole, a significant enhancement can be found in the doubly heavy baryon production.

We investigate the electronic structures and magnetic properties of ZnO doped with N, Cu, and (Cu+N) by using a first principles method and considering the strong correlation effect. It is interesting to compare these three systems. ZnO:N has weak p-type doping and unstable ferromagnetism, while ZnO:Cu becomes insulating due to the Jahn—Teller effect. Cu and N codoping can not only greatly improve the dopability of p-type doping accompanying the Jahn—Teller fading, but also enhance the ferromagnetism at the same time. The calculation results indicate that there is a win-win effect between N and Cu dopants in the ZnO:(Cu+N) system, which could possibly find applications in spintronics besides optoelectronics.

The noise suppression effect and its mechanism are investigated for a composite sheet and a composite film made of glass-covered amorphous CoFeSiBCr wires. Both samples show a significant noise suppression effect. The power loss ratio of the composite sheet is above 80% from 1.6 GHz to 8.5 GHz, and that of the composite film is above 70% from 3.2 GHz to 8.5 GHz even if its thickness is only 0.20 mm. The composite sheet demonstrates high real and imaginary permittivity above 30.7 and low real and imaginary permeability below 1.2. The surface resistivities of the two composite samples are as high as about 3×1012Ω/square. The power loss of the composite containing glass-covered wires should be mainly contributed by dielectric loss derived from electronic polarization and relaxation.

After the prediction of the giant electroresistance effect, much work has been carried out to find this effect in practical devices. We demonstrate a novel way to obtain a large electroresistance (ER) effect in the multilayer system at room temperature. The current-in-plane (CIP) electric transport measurement is performed on the multilayer structure consisting of (011)-Pb(Mg1/3Nb2/3)O3-PbTiO3(PMN-PT)/Ta/Al-O/metal. It is found that the resistance of the top metallic layer shows a hysteretic behavior as a function electric field, which corresponds well with the substrate polarization versus electric field (P—E) loop. This reversible hysteretic R—E behavior is independent of the applied magnetic field as well as the magnetic structure of the top metallic layer and keeps its memory state. This novel memory effect is attributed to the polarization reversal induced electrostatic potential, which is felt throughout the multilayer stack and is enhanced by the dielectric Al-O layer producing unique hysteretic, reversible, and reproducible resistance switching behavior. This novel universal electroresistance effect will open a new gateway to the development of future multiferroic memory devices operating at room temperature.

Binding of methylene blue (MB) and DNA, photosensitization of MB in DNA, and correlation of photosensitization and binding mode are studied at different concentration ratios of DNA and MB. The absorption spectra indicate that the electrostatic binding is the main mode at low γ ratios (γ ≤ 2), while at high γ ratios (γ > 2) the intercalative binding is dominated. Studies on dynamics of photosensitization formation of singlet oxygen (1O2) for MB in DNA are carried out by using time-resolved technology. There are no obvious changes of the singlet oxygen lifetime and the triplet state MB molecule (MB3+*) lifetime at low ratios, they are about 4 μs and 1 μs, respectively. However, we could not obtain the 1O2 lifetime and MB3+* lifetime due to the great decrease of 1O2 phosphorescence signals at high ratios. These results show that the photosensitization and binding mode of MB in DNA possess high correlation. When MB binds with DNA by electrostatic interaction, type-II photosensitization of MB plays a major role in photodynamic effect, the damage of DNA probably could be ascribed to 1O2. However, at high ratios, binding mode between MB and DNA turns to intercalative binding, which greatly weakens the type-II photosensitization process. Charge transfer between MB and DNA possibly becomes the main damage mechanism.

Mg-doped AlxGa1-xN epilayers were grown on AlN/sapphire templates by metal organic chemical vapor deposition (MOCVD) using an indium-assisted growth method. At room temperature, the resistivity of Mg-doped Al0.43Ga0.57N epilayer grown under indium (In) ambient is of the order of 104 Ω-cm, while the resistivity of Mg-doped Al 0.43Ga0.57N grown without In assistance is of the order of 106 Ω-cm. The ultraviolet light-emitting diodes (UV-LEDs) using the In-assisted Mg-doped Al0.43Ga0.57N as the p-type layers were fabricated to verify the function of indium ambient. It is found that there are a lower turn-on voltage and a lower diode series resistance in the UV-LEDs fabricated with p-type Al0.43Ga0.57N layers grown under In-ambient.