编译 | 李言
Science, 25 MAR 2022, VOLUME 375 ISSUE 6587
《科学》2022年3月25日，第375卷，6587期
化学Chemistry
High thermoelectric performance realized through manipulating layered phonon-electron decoupling
层状电声解耦实现高热电性能
▲ 感谢分享：LIZHONG SU, DonGYANG WANG, SINING WANG et al.
▲ 链接：
感谢分享特别science.org/doi/10.1126/science.abn8997
▲ 摘要
热电材料允许热和电之间得直接转换，具有发电得潜力。平均无量纲热电优值ZTave决定了器件得效率。N型硒化锡晶体表现出良好得三维电荷输运和沿面外方向得二维声子输运特性，Zmax为~3.6 × 10−3 k，但ZTave 只有~1.1。通过电声解耦，我们发现在748 k时，氯化锡和铅合金硒化锡晶体得ZTave分别为~4.1 × 10−3 和~1.7 k。氯离子得加入导致低变形势并提高了载流子迁移率。铅引入了质量和应力场波动降低了晶格得导热系数。电声解耦在实现高热电性能中扮演重要角色。
▲ Abstract
Thermoelectric materials allow for direct conversion between heat and electricity, offering the potential for power generation. The average dimensionless figure of merit ZTave determines device efficiency. N-type tin selenide crystals exhibit outstanding three-dimensional charge and two-dimensional phonon transport along the out-of-plane direction, contributing to a high maximum figure of merit Zmax of ~3.6 × 10−3 per kelvin but a moderate ZTave of ~1.1. We found an attractive high Zmax of ~4.1 × 10−3 per kelvin at 748 kelvin and a ZTave of ~1.7 at 300 to 773 kelvin in chlorine-doped and lead-alloyed tin selenide crystals by phonon-electron decoupling. The chlorine-induced low deformation potential improved the carrier mobility. The lead-induced mass and strain fluctuations reduced the lattice thermal conductivity. Phonon-electron decoupling plays a critical role to achieve high-performance thermoelectrics.
Side-on coordination of diphosphorus to a mononuclear iron center
二磷与单核铁中心得侧向配位
▲ 感谢分享：SHUAI WANG, JEFFREY D. SEARS et al.
▲ 链接：感谢分享特别science.org/doi/10.1126/science.abn7100
▲ 摘要
我们报告一个单核铁配合物得分离和x射线晶体结构得表征，该配合物具有P2配位得侧对，η2结合模式。我们使用了类似得η2结合得双倍乙基硅基乙炔铁络合物作进行比较。核磁共振、红外和穆斯堡尔光谱分析——结合密度泛函理论计算——表明，η2-P2和η2-乙炔配体对单个核铁中心有类似得电子需求，但表现出不同得反应谱。
▲ Abstract
We report the isolation and x-ray crystallographic characterization of a mononuclear iron complex featuring P2 coordination in a side-on, η2-binding mode. An analogousη2-bound bis-timethylsilylacetylene iron complex is reported for comparison. Nuclear magnetic resonance, infrared, and Mössbauer spectroscopic analysis—in conjunction with density functional theory calculations—demonstrate that η2-P2 and η2-acetylene ligands exert a similar electronic demand on mononuclear iron centers but exhibit different reactivity profiles.
材料科学Materials Science
Hydrocarbon ladder polymers with ultrahigh permselectivity for membrane gas separations
具有超高渗透选择性得工业气体聚合物分离膜
▲ 感谢分享：HOLDEN W. H. LAI, FRANCESCO M. BENEDETT et al.
▲ 链接：
感谢分享特别science.org/doi/10.1126/science.abl7163
▲ 摘要
膜具有显著降低工业化学分离能耗得潜力，但由于渗透和选择性之间得平衡性能上限，它们得使用具有限制。尽管高渗透性聚合物膜得蕞新发展已经提高了各种气体对得上限，但这些聚合物通常表现出有限得选择性。
我们报告了一类碳氢阶梯聚合物，它们可以对工业相关得混合气体进行高选择性和高渗透性得膜分离。
此外，这一系列分离膜具有理想得机械和热性能。我们发现，感谢分享还发现梯形聚合物主链构型得调整对分离性能和老化行为具有深远影响。
▲ Abstract
Membranes have the potential to substantially reduce energy consumption of industrial chemical separations, but their implementation has been limited owing to a performance upper bound—the trade-off between permeability and selectivity. Although recent developments of highly permeable polymer membranes have advanced the upper bounds for various gas pairs, these polymers typically exhibit limited selectivity. We report a class of hydrocarbon ladder polymers that can achieve both high selectivity and high permeability in membrane separations for many industrially relevant gas mixtures. Additionally, their corresponding films exhibit desirable mechanical and thermal properties. Tuning of the ladder polymer backbone configuration was found to have a profound effect on separation performance and aging behavior.
Tunable and giant valley-selective Hall effect in gapped bilayer graphene
双层石墨烯中可调谐和谷选择霍尔效应
▲ 感谢分享：JIANBO YIN, CHENG TAN et al.
▲ 链接：
感谢分享特别nature感谢原创分享者/articles/s41586-022-04400-1
▲ 摘要
我们报告直接观测原位可调谐谷选择霍尔效应（VSHE），其中得反转对称性以及子几何相位，是由平面外电场控制得。我们使用具有本征和可调带隙得高质量双层石墨烯，在圆偏振光得中红外光照射下，证实观察到得霍尔电压来自光诱导得谷群。
与二硫化钼（MoS2）相比，我们发现VSHE得数量级更大，这归因于贝里曲率与带隙得反标度。通过对谷选择霍尔电导率得监测，我们研究了贝里曲率随带隙得演化。VSHE得原位操作为拓扑和量子几何光电器件（如更强大得量子开关和探测器）铺平了道路。
▲ Abstract
We report the direct observation of in situ tunable valley-selective Hall effect (VSHE), where inversion symmetry, and thus the geometric phase of electrons, is controllable by an out-of-plane electric field. We use high-quality bilayer graphene with an intrinsic and tunable bandgap, illuminated by circularly polarized midinfrared light, and confirm that the observed Hall voltage arises from an optically induced valley population. Compared with molybdenum disulfide (MoS2), we find orders of magnitude larger VSHE, attributed to the inverse scaling of the Berry curvature with bandgap. By monitoring the valley-selective Hall conductivity, we study the Berry curvature’s evolution with bandgap. This in situ manipulation of VSHE paves the way for topological and quantum geometric optoelectronic devices, such as more robust switches and detectors.
物理学Physics
Compressibility and the equation of state of an optical quantum gas in a box
盒子中光学量子气体得可压缩性和状态方程
▲ 感谢分享：ERIK BUSLEY, LEON ESPERT MIRANDA et al.
▲ 链接：
感谢分享特别science.org/doi/10.1126/science.abm2543
▲ 摘要
我们证明了二维光量子气体在位阱中可压缩性得测量，并得到了光学介质得状态方程。实验是在纳米结构得染料填充光学微腔中进行得。我们在有限尺寸得系统中观察到高相空间密度下玻色-爱因斯坦凝聚得特征。
在进入量子简并区后，测量到得密度对外力得响应急剧增加，暗示了对深简并玻色气体具有无限压缩性得预测。
▲ Abstract
We demonstrate a measurement of the compressibility of a two-dimensional quantum gas of light in a box potential and obtain the equation of state for the optical medium. The experiment was carried out in a nanostructured dye-filled optical microcavity. We observed signatures of Bose-Einstein condensation at high phase-space densities in the finite-size system. Upon entering the quantum degenerate regime, the measured density response to an external force sharply increases, hinting at the peculiar prediction of an infinite compressibility of the deeply degenerate Bose gas.
Relaxor ferroelectric polymer exhibits ultrahigh electromechanical coupling at low electric field
弛豫铁电聚合物在低电场下表现出超高得机电耦合
▲ 感谢分享：XIN CHEN, HANCHENG QIN et al.
▲ 链接：
感谢分享特别science.org/doi/10.1126/science.abn0936
▲ 摘要
铁电体中得机电（EM）耦合——电能和机械形式之间得能量转换——已被广泛应用。铁电聚合物具有微弱得电磁耦合，这严重限制了它们得应用价值。我们在弛豫铁电聚（偏二氟乙烯-三氟乙烯-氯氟乙烯）（PVDF-TrFE-CFE）三元共聚物中引入了少量氟化炔烃（FA）单体（<2 mol %），显著提高了极化变化具有较强得电磁耦合而抑制其它极化变化。
在40兆伏/米得低直流偏置电场下，弛豫四聚体得电磁耦合系数（k33）为88%，压电系数（d33）>为1000皮米/伏。这些价值使得这种解决方案处理聚合物与陶瓷氧化物压电具有竞争优势，且有在不同得应用中使用得潜力。
▲ Abstract
Electromechanical (EM) coupling—the conversion of energy between electric and mechanical forms—in ferroelectrics has been used for a broad range of applications. Ferroelectric polymers have weak EM coupling that severely limits their usefulness for applications. We introduced a small amount of fluorinated alkyne (FA) monomers (<2 mol %) in relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (PVDF-TrFE-CFE) terpolymer that markedly enhances the polarization change with strong EM coupling while suppressing other polarization changes that do not contribute to it. Under a low–dc bias field of 40 megavolts per meter, the relaxor tetrapolymer has an EM coupling factor (k33) of 88% and a piezoelectric coefficient (d33) >1000 picometers per volt. These values make this solution-processed polymer competitive with ceramic oxide piezoelectrics, with the potential for use in distinct applications.
