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• ### Giant converse magnetoelectric effect in a multiferroic heterostructure with polycrystalline Co2FeSi

We show giant converse magnetoelectric effect in a multiferroic heterostructure consisting of ferromagnetic Heusler alloy Co2FeSi and ferroelectric-oxide Pb(Mg1/3Nb2/3)O3-PbTiO3 for an electric-field control of magnetization vectors. In this system, the non-volatile and repeatable magnetization vector switchings in remanent states are also demonstrated. This approach can lead to a new solution to the reduction in the write power in spintronic memory architectures at room temperature.

• Shumpei Fujii
• Takamasa Usami
• Kohei Hamaya
Article Open Access
• ### Triplet-radical spin entanglement: potential of molecular materials for high-temperature quantum information processing

An illustration of the optically controlled entanglement between a radical spin and a triplet state on an optically active moiety such as a phthalocyanine molecule. The optical excitations and the resulting strong exchange interactions, in combination with the recent spin manipulation in molecules at high temperature, imply this entangling mechanism has a great potential for room temperature quantum computing.

• Lin Ma
• Jiawei Chang
• Hai Wang
Article Open Access
• ### Role of magnetostriction on power losses in nanocrystalline soft magnets

We formulated micromagnetic simulation models of nanocrystalline soft magnetic materials including effects of magnetostriction, and simulated motions of domain walls to clarify mechanism of energy dissipations in the nanocrystalline soft magnetic materials. The magnetostriction is nonuniformly distributed, and magnetic energy induced by external field is converted into elastic energy due to the magnetostriction. This energy consumption generates an excess loss in the nanocrystalline soft magnetic materials even there is no eddy current. The simulation results enable us to reduce the core loss in the nanocrystalline soft magnetic materials.

• Hiroshi Tsukahara
• Hiroshi Imamura
• Kanta Ono
Article Open Access
• ### Unidentified major p-type source in SnSe: Multivacancies

Single Sn vacancies are dominant in slow solidification speed, while multivacancies are dominant in high solidification speed SnSe crystals. The multivacancies also provide hole carrier to the crystal and are major p-type sources in high solidification speed SnSe crystals especially in polycrystalline SnSe.

• Van Quang Nguyen
• Thi Ly Trinh
• Sunglae Cho
Article Open Access
• ### In-plane optical and electrical anisotropy in low-symmetry layered GeS microribbons

Two-dimensional distorted orthorhombic GeS microribbons has been synthesized applying vapor-liquid-solid and vapor-solid mechanism-based chemical vapor transport. Polarized Raman and photoluminescence characterizations show the significantly angle-dependent intensity and anisotropic optical properties. Additionally, we probed the anisotropic electric properties by fabricating back-gate cross-shaped field effect transistors. In-plane direct current measurement demonstrated the charge carrier transport anisotropy and its anisotropic current ratio can be linearly adjusted by changing the gate voltage under dark and illumination conditions.

• Zhangfu Chen
• Woohyun Hwang
• Heon-Jin Choi
Article Open Access
• ### Individually addressable and flexible pressure sensor matrixes with ZnO nanotube arrays on graphene

A novel technique is demonstrated for the fabrication of individually addressable, high-density, flexible pressure sensor arrays composed of 1D ZnO nanotubes on graphene. The individually addressable pixel matrix was fabricated by arranging the top and bottom electrodes of the sensors in a crossbar configuration. A high spatial resolution of 1058 dpi was achieved for a Schottky diode-based force/pressure sensor composed of piezoelectric ZnO nanotubes on a flexible substrate.

• Junbeom Park
• Ramesh Ghosh
• Gyu-Chul Yi
Article Open Access
• ### Mechanically resilient integrated electronics realized using interconnected 2D gold-nanosheet elastomeric electrodes

A mechanically percolated network of 2D gold nanosheets embedded within a PDMS elastomer enables the realization of elastomeric electrodes with superior mechanical sustainability and high electrical conductivity. Owing to such highly durable elastomeric electrodes facilitate the development of elastomeric electronics, including transistors, inverters, NOR, and NAND, which is expected to broaden the scope of soft electronic applications.

• Seojun Heo
• Seongsik Jeong
• Hae-Jin Kim
Article Open Access
• ### Porous microcapsules encapsulating β cells generated by microfluidic electrospray technology for diabetes treatment

The β-cell microcapsules prepared by the microfluidic electrospray method were transplanted into the omentum pouch of mice for intelligent release of insulin to treat diabetes. Studies have shown that microcapsules can encapsulate cells while allowing nutrients and metabolites to enter and exit. This ability helps protect cells, improve cell activity, and reduce inflammation. In addition, the β-cell microcapsules can intelligently release insulin. The constructed living cell biosystem was further demonstrated its potential as artificial islets to be transplanted into diabetic mice omentum pouch to control blood glucose levels and thus treat diabetes of mice.

• Xiaoyu Liu
• Yunru Yu
• Ling Li
Article Open Access
• ### Robust dual topological insulator phase in NaZnBi

We report that recently synthesized NaZnBi is a new dual topological insulator, with $${\Bbb Z}_2$$ ${\mathbb{Z}}_{2}$ indices $$(\nu _0;\nu _1\nu _2\nu _3) = (1;000)$$ $\left({\nu }_{0};{\nu }_{1}{\nu }_{2}{\nu }_{3}\right)=\left(1;000\right)$ and odd mirror Chern numbers ±1, based on the first-principles calculations. NaZnBi, which crystallizes in a tetragonal structure with the P4/nmm space group, consists of ZnBi layers and embedded Na atoms. The (100) surface electronic structure exhibits the gapless surface states, which connect the valence and conduction bulk bands. These gapless surface states form the topological Dirac point at the Brillouin zone center $$\overline{\Gamma}$$ $\overline{\mathrm{\Gamma }}$ . This characteristic clearly shows the topological insulating phase in NaZnBi. Moreover, by applying an external magnetic field in various directions, we verify that the topological Dirac point at $$\overline {\Gamma}$$ $\overline{\mathrm{\Gamma }}$ is protected by the time-reversal and mirror symmetries, and confirm that NaZnBi belongs to the class of dual topological insulators.

• Hyunggeun Lee
• Yoon-Gu Kang
• Kee Joo Chang
Article Open Access
• ### Preparation of dual-cross network polymers by the knitting method and evaluation of their mechanical properties

The “molecular knitting method” improves toughness and Young’s modulus. We prepared dual cross-network (DC) elastomers with a knitting structure and single movable cross-network elastomers with penetrating polymers (SCP elastomers) by swelling the single movable cross-network (SC) elastomers in liquid monomers. The DC elastomers showed a high toughness and a high Young’s modulus. SAXS indicated that the DC elastomers exhibited heterogeneity at the nanoscale. The DC elastomers showed a significantly broader relaxation time distribution than the SC and SCP elastomers. Thus, the nanoscale heterogeneity and broader relaxation time distribution were important to increase toughness.

• Yusaku Kawai
• Junsu Park
• Yoshinori Takashima
Article Open Access
• ### Suppressed phonon conduction by geometrically induced evolution of transport characteristics from Brownian motion into Lévy flight

Despite extensive previous research, the suppression in phonon conduction at the nanoscale still calls into questions on the interaction of phonons with various sources of boundary scatterings. In this work, a combination of Boltzmann transport model and the experiments finds that the bridges contribute to phonon mean free paths proportional to its volume fraction despite its negligible contribution to net heat flux. A statistical analysis of boundary scattering reveals that transport characteristics of phonon evolves from Brownian motion to Lévy walk due to phonons trapped within the bridges.

• Yongjoon Kim
• Takashi Kodama
• Woosung Park
Article Open Access
• ### Nanoscale limit of the thermal conductivity in crystalline silicon carbide membranes, nanowires, and phononic crystals

In this work, we systematically study heat conduction in SiC nanostructures, including nanomembranes, nanowires, and phononic crystals. Our measurements show that the thermal conductivity of nanostructures is several times lower than that in bulk and the values scale proportionally to the narrowest dimension of the structures. Additionally, we probed phonon mean free path and coherent heat conduction in these nanostructures. Our theoretical model links the observed suppression of heat conduction with the surface phonon scattering, which limits the phonon mean free path and thus reduces the thermal conductivity.

• Roman Anufriev
• Yunhui Wu
• Masahiro Nomura
Article Open Access
• ### Reversible colossal barocaloric effect dominated by disordering of organic chains in (CH3–(CH2)n−1–NH3)2MnCl4 single crystals

For the emergent colossal, reversible barocaloric effect in organic–inorganic perovskite hybrids (CH3–(CH2)n−1–NH3)2MnCl4 (n = 9, 10), we successfully grew a single crystal, and the underlying mechanism was determined by high-resolution SC-XRD, IR spectroscopy and DFT calculations. The drastic transformation of organic chains confined to the metallic frame from ordered rigidity to disordered flexibility is responsible for the large phase-transition entropy, which is comparable to the melting entropy of organic chains. The result provides new insights into designing novel barocaloric materials by utilizing the disordering of organic chains of organic–inorganic hybrid materials.

• Yihong Gao
• Hongxiong Liu
• Baogen Shen
Article Open Access
• ### Possible permanent Dirac- to Weyl-semimetal phase transition by ion implantation

(Left, above) Schematic diagram describing the process of the Au implantation into the Dirac semimetal (DSM) Bi0.96Sb0.04. (Left, below) Positive longitudinal magnetic resistance (LMR) is observed in the crystal without ion implantation, but negative LMR behavior becomes apparent for ϕG ≥ 3.2 × 1016 Au cm−2 (≡ ϕC, critical implant fluence), and reaches a maximum for ϕG = 8.0 × 1016 Au cm−2. (Middle) Quantum oscillation parameters for the β Fermi pockets showing abrupt changes near ϕC, typical of phase transition. No such behavior is observed for the α Fermi pockets. (Right) A drastic change in the Raman spectra is observed for ϕG ≥ ϕC. In particular, a new peak appears at 85.7 cm−1, between the well-known Raman modes, suggesting that the inversion symmetry breaking in the crystal occurred for ϕG ≥ ϕC, resulting in the transition of the DSM to a Weyl semimetal.

• Won Jun Lee
• Suk-Ho Choi
Article Open Access
• ### Large barocaloric effect in intermetallic La1.2Ce0.8Fe11Si2H1.86 materials driven by low pressure

A rare-earth intermetallic La-Ce-Fe-Si-H has been directly measured to cool 8 K when it is under a 1 kbar pressure. This barocaloric strength significantly outperforms those in previously reported phase-transitioned alloys. A multifield-dependent neutron diffraction has revealed that the large isotropic transition volume change for La-Ce-Fe-Si-H plays a crucial role in exploring the giant barocaloric effect.

• Yanfeng Liu
• Xinqi Zheng
• Jian Liu
Article Open Access
• ### Gelation and anomalous viscosity dynamics in aqueous dispersions of synthetic hectorite

Clay nanosheets (CNSs) of synthetic hectorite have been used for synthesizing advanced functional gels that exhibit high mechanical toughness and many unprecedented characteristics, such as cell harvesting, instant strong adhesion, and self-healing. Upon varying the pH and salt concentration, the aqueous CNS dispersions were found to exhibit a maximum viscosity accompanied by gelation, in addition to large and complex time-dependent viscosity changes in the static state. Such anomalous viscosity dynamics depended on the types of clay and acid (salt), temperature, number of repetitions, and agitation conditions; their mechanisms were also discussed in terms of variations in the CNS microstructures.

• Yuji Kimura
• Shoichi Shimizu
• Kazutoshi Haraguchi
Article Open Access
• ### Precise orientation control of a liquid crystal organic semiconductor via anisotropic surface treatment

It is the first work demonstrating the modulating opto-electrical signals of organic semiconductors by the liquid crystal properties. Through flipping the anisotropic surface treatment-based sandwich cells, the liquid crystal organic semiconductor responds to the given surface anchoring condition with temperature gradient, showing tunable molecular orientation with the corresponding charge carrier mobility of organic field-effect transistors.

• Moon Jong Han
• Dayan Wei
• Dong Ki Yoon
Article Open Access
• ### Smart hydrogels with wide visible color tunability

Smart hydrogels with wide visible color tunability and highly tunable color saturations and transmittances are created. The hydrogels with flexible light-interacting configuration changes, can harvest energy from selected wavelengths of visible light to display complementary colors across a wide visible range. The hydrogels are used as optical filters and colorimetric sensors to demonstrate their versatility.

• Guo-Yu Wen
• Xing-Long Zhou
• Liang-Yin Chu
Article Open Access
• ### Detection of cracked teeth using a mechanoluminescence phosphor with a stretchable photodetector array

We demonstrate the early diagnosis of cracked tooth syndrome (CTS) by imaging the microcracks on a tooth in the closed mouth condition using a mechanoluminescence (ML) phosphor and a stretchable and self-healable photodetector array that can conformably cover a single tooth. This method does not require sophisticated equipment and hence will be useful in the early diagnosis of CTS. To the best of our knowledge, this is the first report on the use of ML for the detection of the position of tooth cracks.

• Ha Jun Kim
• Sangyoon Ji
• Won Bin Im
Article Open Access
• ### Controllable tuning of polymetallic Co-Ni-Ru-S-Se ultrathin nanosheets to boost electrocatalytic oxygen evolution

In this study, regulating composition and morphology of the trimetallic Co-Ni-Ru sulfoselenide and bimetallic sulfoselenide nanosheets are designed for efficient and durable OER electrocatalysts. The sheet structure has a large specific surface area to promote the contact between the catalyst and the electrolyte. Density functional theory (DFT) calculations show that appropriate Ru and Ni doping simultaneously (Co-Ni-Ru-S-Se) can increase the density of states of the Fermi level, resulting in excellent charge density and low intermediate adsorption energy.

• Wei Deng
• Wenshuo Xie
• Fei Jiang
Article Open Access