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論文

Gate-tunable resistance drops related to local superconducting gaps in thin TaS$$_2$$ layers on SrTiO$$_3$$ substrates

小杉 美央子*; 齊藤 英治; 吉川 貴史*; 他11名*

APL Materials (Internet), 11(8), p.081106_1 - 081106_6, 2023/08

https://doi.org/10.1063/5.0147818
 被引用回数：1 パーセンタイル：13.37(Nanoscience & Nanotechnology)

Strontium titanate [SrTiO$$_{3}$$ (STO)], a perovskite oxide with an extremely high gate-tunable dielectric constant ($$varepsilon$$) due to quantum paraelectric phases, is attracting considerable attention for yielding various physical phenomena when two-dimensional (2D) layers are integrated. Superconductivity is such a typical phenomenon. However, the influence of the STO substrates on enhancing transition temperatures ($$T$$$$_{rm c}$$) for (atomically) thin 2D flakes attached to them has been rarely investigated. Here, we report gate-tunable and gradual four-terminal resistance drops with critical onset $$T$$ ($$T$$$$_{rm CR}$$) and scanning tunneling spectroscopy (STS) spectra in devices comprising thin TaS$$_{2}$$ flakes attached on monolayer hexagonal boron nitride (hBN) spacer/STO substrates. Observation of STS spectra confirms the presence of local superconducting gaps. (similar to 1.5 meV) with transition $$T$$($$T_{Delta rm C})$$ three-times higher than previous reports of $$T$$$$_{rm c}$$ under absent pressure and strong position dependence of $${Delta}$$. Depending on $$Delta$$ on back gate voltages ($$V$$$$_{rm bg}$$) and magnetic fields, there is a strong correlation between $$T$$$$_{rm CR}$$ and the onset $$T$$$$_{rm c}$$ of superconductivity, implying an enhancement of approximately five times compared with the previous highest-onset $$T$$$$_{rm c}$$ values without pressure as the applied $$V$$$$_{rm bg}$$ increases. The high onset $$T$$$$_{rm c}$$ and. are discussed based on screening of the long-range Coulomb interaction (CI) due to the high-$$varepsilon$$ of SrTiO$$_{3}$$, while the short-ranged CI remains strong in the 2D limit, causing the superconductivity. Using a monolayer hBN/SrTiO$$_{3}$$ substrate with $$V$$$$_{rm bg}$$ opens doors to $$T$$$$_{rm c}$$ enhancement in thin superconducting layers integrated on it and wide application due to the solid-state high-$$varepsilon$$ substrates.

論文

One-pot synthesis of superparamagnetically modified zeolite chabazite for removal of Cs$$^{+}$$ from radioactively contaminated water

伊藤 あずさ; Karmaoui, M.*; Thirunavukkarasu, G.*; Hriljac, J. A.*

APL Materials (Internet), 11(4), p.041105_1 - 041105_9, 2023/04

https://doi.org/10.1063/5.0139282
 被引用回数：3 パーセンタイル：27.36(Nanoscience & Nanotechnology)

Composites of zeolite Na-chabazite particles with attached superparamagnetic nanoparticles of Fe$$_{3}$$O$$_{4}$$ and CoFe$$_{2}$$O$$_{4}$$ ferrite spinels have been produced using a novel solvothermal route. These have been characterized by a combination of techniques including powder X-ray diffraction, X-ray fluorescence spectroscopy, Raman spectroscopy, vibrating sample magnetometry and both scanning and transmission electron microscopy. These confirm the nature of the attached nanoparticles and the microscope images show a good dispersion of nanoparticles with a narrow size range deposit uniformly on the surface of the zeolite particles. The magnetisation is of sufficient strength to allow magnetic separation from solution. Both time and pH dependent Cs uptake experiments show the magnetised systems are still excellent for the rapid uptake of Cs via an ion exchange process with no reduction in property due to the attached nanoparticles.

論文

Li$$_{4}$$FeH$$_{6}$$; Iron-containing complex hydride with high gravimetric hydrogen density

齋藤 寛之; 高木 成幸*; 松尾 元彰*; 飯島 祐樹*; 遠藤 成輝*; 青木 勝敏*; 折茂 慎一*

APL Materials (Internet), 2(7), p.076103_1 - 076103_7, 2014/07

https://doi.org/10.1063/1.4886219
 被引用回数：25 パーセンタイル：68.14(Nanoscience & Nanotechnology)

Li$$_{4}$$FeH$$_{6}$$, which has the highest gravimetric hydrogen density of iron-containing complex hydrides reported so far, is synthesized by hydrogenation of a powder mixture of iron and LiH above 6.1 GPa at 900 $$^{circ}$$C. ${it In situ}$ synchrotron radiation X-ray diffraction measurements reveal that while kinetics require high temperature and thus high pressure for the synthesis, Li$$_{4}$$FeH$$_{6}$$ is expected to be thermodynamically stable slightly below room temperature at ambient pressure; further synthetic studies to suppress the kinetic effects may enable us to synthesize Li$$_{4}$$FeH$$_{6}$$ at moderate pressures. Li$$_{4}$$FeH$$_{6}$$ can be recovered at ambient conditions where Li$$_{4}$$FeH$$_{6}$$ is metastable.

論文

Synthesis and formation process of Al$$_{2}$$CuH$$_{x}$$; A New class of interstitial aluminum-based alloy hydride

齋藤 寛之; 高木 成幸*; 遠藤 成輝; 町田 晃彦; 青木 勝敏; 折茂 慎一*; 片山 芳則

APL Materials (Internet), 1(3), p.032113_1 - 032113_7, 2013/09

https://doi.org/10.1063/1.4821632
 被引用回数：15 パーセンタイル：52.02(Nanoscience & Nanotechnology)

Aluminum-based alloy hydride Al$$_{2}$$CuH$$_{x}$$ (x$$sim$$1) is synthesized by hydrogenating Al$$_{2}$$Cu alloy using high-temperature and high-pressure hydrogen atmosphere. Al$$_{8}$$Cu square antiprisms in Al$$_{2}$$Cu twist around the c axis of a tetragonal unit cell by hydrogenation. The twist enlarges the interstitial spaces for accommodating hydrogen atoms which align linearly parallel to the c axis in Al$$_{2}$$CuH$$_{x}$$. Thermodynamic stability of Al$$_{2}$$CuH$$_{x}$$ results from the balance of stabilization by H 1s and Al 3sp hybridization and destabilization owing to the Fermi-level lifting upon hydrogenation. The crystal and electronic structures of Al$$_{2}$$CuH$$_{x}$$ illustrate the formation of an interstitial hydride of aluminum-based alloy.

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