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1. In-plane anisotropic two-dimensional materials for twistronics

   https://doi.org/10.1088/1361-6528/ad2c53  

   Kim, Hangyel; Kim, Changheon; Jung, Yeonwoong; Kim, Namwon; Son, Jangyup; Lee, Gwan-Hyoung (April 2024, Nanotechnology)

   Abstract In-plane anisotropic two-dimensional (2D) materials exhibit in-plane orientation-dependent properties. The anisotropic unit cell causes these materials to show lower symmetry but more diverse physical properties than in-plane isotropic 2D materials. In addition, the artificial stacking of in-plane anisotropic 2D materials can generate new phenomena that cannot be achieved in in-plane isotropic 2D materials. In this perspective we provide an overview of representative in-plane anisotropic 2D materials and their properties, such as black phosphorus, group IV monochalcogenides, group VI transition metal dichalcogenides with 1T′ and T_dphases, and rhenium dichalcogenides. In addition, we discuss recent theoretical and experimental investigations of twistronics using in-plane anisotropic 2D materials. Both in-plane anisotropic 2D materials and their twistronics hold considerable potential for advancing the field of 2D materials, particularly in the context of orientation-dependent optoelectronic devices. 

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2. Controlling the roll-to-helix transformation in electron-beam-patterned gel-based micro-ribbons

   https://doi.org/10.1039/D4SM00666F  

   Wu, Xinpei; Zhang, Teng; Libera, Matthew (October 2024, Soft Matter)

   Shape changes in electron-beam patterned poly(acrylic acid) can be controlled by the many patterning parameters to create gel-based ribbons with both in-plane and out-of-plane pH-dependent swelling anisotropies. 

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3. Black Arsenic: A Layered Semiconductor with Extreme In‐Plane Anisotropy

   https://doi.org/10.1002/adma.201800754  

   Chen, Yabin; Chen, Chaoyu; Kealhofer, Robert; Liu, Huili; Yuan, Zhiquan; Jiang, Lili; Suh, Joonki; Park, Joonsuk; Ko, Changhyun; Choe, Hwan_Sung; et al (June 2018, Advanced Materials)

   Abstract 2D layered materials have emerged in recent years as a new platform to host novel electronic, optical, or excitonic physics and develop unprecedented nanoelectronic and energy applications. By definition, these materials are strongly anisotropic between the basal plane and cross the plane. The structural and property anisotropies inside their basal plane, however, are much less investigated. Black phosphorus, for example, is a 2D material that has such in‐plane anisotropy. Here, a rare chemical form of arsenic, called black‐arsenic (b‐As), is reported as a cousin of black phosphorus, as an extremely anisotropic layered semiconductor. Systematic characterization of the structural, electronic, thermal, and electrical properties of b‐As single crystals is performed, with particular focus on its anisotropies along two in‐plane principle axes, armchair (AC) and zigzag (ZZ). The analysis shows that b‐As exhibits higher or comparable electronic, thermal, and electric transport anisotropies between the AC and ZZ directions than any other known 2D crystals. Such extreme in‐plane anisotropies can potentially implement novel ideas for scientific research and device applications. 

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4. Types of noncovalent bonds within complexes of thiazole with CF ₄ and SiF ₄

   https://doi.org/10.1039/D4CP00057A  

   Scheiner, Steve; Amonov, Akhtam (February 2024, Physical Chemistry Chemical Physics)

   The five-membered heteroaromatic thiazole molecule contains a number of electron-rich regions that could attract an electrophile, namely the N and S lone pairs that lie in the molecular plane, and π-system areas above the plane. 

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5. First-principles prediction of thermal conductivity of bulk hexagonal boron nitride

   https://doi.org/10.1063/5.0210935  

   Guo, Ziqi; Han, Zherui; Alkandari, Abdulaziz; Khot, Krutarth; Ruan, Xiulin (April 2024, Applied Physics Letters)

   Despite its importance, a sophisticated theoretical study of thermal conductivity in bulk h-BN has been lacking to date. In this study, we predict thermal conductivity in bulk h-BN crystals using first-principles predictions and the Boltzmann transport equation. We consider three-phonon (3ph) scattering, four-phonon (4ph) scattering, and phonon renormalization. Our predicted thermal conductivity is 363 and 4.88 W/(m K) for the in-plane and out-of-plane directions at room temperature, respectively. Further analysis reveals that 4ph scattering reduces thermal conductivity, while phonon renormalization weakens phonon anharmonicity and increases thermal conductivity. Eventually, the in-plane and out-of-plane thermal conductivities show intriguing ∼T−0.627 and ∼T−0.568 dependencies, respectively, far deviating from the traditional 1/T relation. 

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