An ytterbium quantum gas microscope with narrow-line laser cooling

We demonstrate site-resolved imaging of individual bosonic $^{174}\mathrm{Yb}$ atoms in a Hubbard-regime two-dimensional optical lattice with a short lattice constant of 266 nm. To suppress the heating by probe light with the $^1S_0$-$^1P_1$ transition of the wavelength $\lambda$ = 399 nm for high-resolution imaging and preserve atoms at the same lattice sites during the fluorescence imaging, we simultaneously cool atoms by additionally applying narrow-line optical molasses with the $^1S_0$-$^3P_1$ transition of the wavelength $\lambda$ = 556 nm. We achieve a low temperature of $T = 7.4(1.3)\ \mu\mathrm{K}$, corresponding to a mean oscillation quantum number along the horizontal axes of 0.22(4) during imaging process. We detect on average 200 fluorescence photons from a single atom within 400 ms exposure time, and estimate the detection fidelity of 87(2)%. The realization of a quantum gas microscope with enough fidelity for Yb atoms in a Hubbard-regime optical lattice opens up the possibilities for studying various kinds of quantum many-body systems such as Bose and Fermi gases, and their mixtures, and also long-range-interacting systems such as Rydberg states.Comment: 14 pages, 6 figure

An Enantioselective Synthesis of 2-Imidazolidinones through Bifunctional Thiourea-Catalyzed Tandem Mannich/Cyclization of Isocyanatomalonate Diester

A chiral bifunctional thiourea-catalyzed Mannich reaction of diethyl 2-isocyanatomalonate with N-sulfonylimines was described. The tandem cyclization proceeded smoothly after Mannch reaction, directly furnishing chiral 2-imidazolidinones in 72‒99% yields with 83‒98% ees. Sterically demanding sulfonyl group was crucial for aliphatic imines to afford the corresponding product in high enantioselectivity

Interface and oxide trap states of SiO2/GaN metal–oxide–semiconductor capacitors and their effects on electrical properties evaluated by deep level transient spectroscopy

The relationship between the electrical properties and the carrier trap properties of the SiO2/GaN metal–oxide–semiconductor (MOS) capacitors was investigated using electrical measurements and deep level transient spectroscopy (DLTS). The capacitance–voltage (C–V) measurement showed that the frequency dispersion of the C–V curves became smaller after an 800 °C annealing in O2 ambient. DLTS revealed that before the annealing, the interface trap states, in a broad energy range above the midgap of GaN, were detected with the higher interface state density at around 0.3 and 0.9 eV below the conduction band minimum (Ec) of GaN. Moreover, the oxide trap states were formed at around 0.1 eV below the Ec of GaN, plausibly indicating a slow electron trap with a tunneling process. Although both trap states affect the electrical reliability and insulating property of the SiO2/GaN MOS capacitors, they were found to drastically decrease after the annealing, leading to the improvement of the electrical properties.Shingo Ogawa, Hidetoshi Mizobata, Takuma Kobayashi, Takayoshi Shimura, Heiji Watanabe; Interface and oxide trap states of SiO2/GaN metal–oxide–semiconductor capacitors and their effects on electrical properties evaluated by deep level transient spectroscopy. J. Appl. Phys. 7 September 2023; 134 (9): 095704. https://doi.org/10.1063/5.016589

Control on the density and optical properties of color centers at SiO2/SiC interfaces by oxidation and annealing

Color centers in solids can serve as single photon emitters (SPEs) those are important in many quantum applications. Silicon carbide (SiC) is a promising host for color centers because of its well-established crystal growth and device technologies. Although color centers with extremely high brightness were found at the silicon dioxide (SiO2)/SiC interface, controlling their density and optical properties remains a challenge. In this study, we demonstrate control over the color centers at the SiO2/SiC interface by designing the oxidation and annealing conditions. We report that post-oxidation CO2 annealing has the ability to reduce the color centers at the interface and form well-isolated SPEs with bright emission. We also discuss the correlation between the color centers and electrically active defects.Takato Nakanuma, Kosuke Tahara, Katsuhiro Kutsuki, Takayoshi Shimura, Heiji Watanabe, Takuma Kobayashi; Control on the density and optical properties of color centers at SiO2/SiC interfaces by oxidation and annealing. Appl. Phys. Lett. 4 September 2023; 123 (10): 102102. https://doi.org/10.1063/5.016674

Erosion control effect of red soil such as Kunigami mji soil by the addition of soil conditioner

Kunigami maji soil is a red soil that distributes in the central north of the main island of Okinawa Prefecture, Since this soil is abundant in fine particles and poor in coagulation force, it is extremely vulnerable to water, causing severe soil runoff when it faces rainfall. The muddy water generated by soil runoff inflicts serious effects on downstream territories, farm fields, rivers and oceans. Muddy water is factor to pollute water environment and destroy ecosystem. This research used a soil conditioner to control soil loss, and examined its control effect. As the soil conditioner, E-soiru was used. In an experiment using artificial rainfall, the amount of dispersed soil occupied about 20-30% of the amount of eroded soil, showing that this factor cannot be neglected. By blending E-soiru, the amount of eroded soil decreased by 39-92% at an inclination of 1.7° and by 59-89% at an inclination of 8.0°. The result showed the significant effect of the addition of E-soiru on soil loss control. In particular, when the volume ratio of Kunigami maji soil and E-soiru was at 1:05, the mixture showed the maximum effect