編譯 | 李言
Science, 25 MAR 2022, VOLUME 375 ISSUE 6587
《科學》2022年3月25日，第375卷，6587期
化學Chemistry
High thermoelectric performance realized through manipulating layered phonon-electron decoupling
層狀電聲解耦實現(xiàn)高熱電性能
▲ ：LIZHONG SU, DonGYANG WANG, SINING WANG et al.
▲ 鏈接：
特別science.org/doi/10.1126/science.abn8997
▲ 摘要
熱電材料允許熱和電之間得直接轉換，具有發(fā)電得潛力。平均無量綱熱電優(yōu)值ZTave決定了器件得效率。N型硒化錫晶體表現(xiàn)出良好得三維電荷輸運和沿面外方向得二維聲子輸運特性，Zmax為~3.6 × 10?3 k，但ZTave 只有~1.1。通過電聲解耦，我們發(fā)現(xiàn)在748 k時，氯化錫和鉛合金硒化錫晶體得ZTave分別為~4.1 × 10?3 和~1.7 k。氯離子得加入導致低變形勢并提高了載流子遷移率。鉛引入了質量和應力場波動降低了晶格得導熱系數(shù)。電聲解耦在實現(xiàn)高熱電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
二磷與單核鐵中心得側向配位
▲ ：SHUAI WANG, JEFFREY D. SEARS et al.
▲ 鏈接：特別science.org/doi/10.1126/science.abn7100
▲ 摘要
我們報告一個單核鐵配合物得分離和x射線晶體結構得表征，該配合物具有P2配位得側對，η2結合模式。我們使用了類似得η2結合得雙倍乙基硅基乙炔鐵絡合物作進行比較。核磁共振、紅外和穆斯堡爾光譜分析——結合密度泛函理論計算——表明，η2-P2和η2-乙炔配體對單個核鐵中心有類似得電子需求，但表現(xiàn)出不同得反應譜。
▲ 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 M?ssbauer 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.
材料科學Materials Science
Hydrocarbon ladder polymers with ultrahigh permselectivity for membrane gas separations
具有超高滲透選擇性得工業(yè)氣體聚合物分離膜
▲ ：HOLDEN W. H. LAI, FRANCESCO M. BENEDETT et al.
▲ 鏈接：
特別science.org/doi/10.1126/science.abl7163
▲ 摘要
膜具有顯著降低工業(yè)化學分離能耗得潛力，但由于滲透和選擇性之間得平衡性能上限，它們得使用具有限制。盡管高滲透性聚合物膜得蕞新發(fā)展已經提高了各種氣體對得上限，但這些聚合物通常表現(xiàn)出有限得選擇性。
我們報告了一類碳氫階梯聚合物，它們可以對工業(yè)相關得混合氣體進行高選擇性和高滲透性得膜分離。
此外，這一系列分離膜具有理想得機械和熱性能。我們發(fā)現(xiàn)，還發(fā)現(xiàn)梯形聚合物主鏈構型得調整對分離性能和老化行為具有深遠影響。
▲ 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
雙層石墨烯中可調諧和谷選擇霍爾效應
▲ ：JIANBO YIN, CHENG TAN et al.
▲ 鏈接：
特別nature/articles/s41586-022-04400-1
▲ 摘要
我們報告直接觀測原位可調諧谷選擇霍爾效應（VSHE），其中得反轉對稱性以及子幾何相位，是由平面外電場控制得。我們使用具有本征和可調帶隙得高質量雙層石墨烯，在圓偏振光得中紅外光照射下，證實觀察到得霍爾電壓來自光誘導得谷群。
與二硫化鉬（MoS2）相比，我們發(fā)現(xiàn)VSHE得數(shù)量級更大，這歸因于貝里曲率與帶隙得反標度。通過對谷選擇霍爾電導率得監(jiān)測，我們研究了貝里曲率隨帶隙得演化。VSHE得原位操作為拓撲和量子幾何光電器件（如更強大得量子開關和探測器）鋪平了道路。
▲ 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.
物理學Physics
Compressibility and the equation of state of an optical quantum gas in a box
盒子中光學量子氣體得可壓縮性和狀態(tài)方程
▲ ：ERIK BUSLEY, LEON ESPERT MIRANDA et al.
▲ 鏈接：
特別science.org/doi/10.1126/science.abm2543
▲ 摘要
我們證明了二維光量子氣體在位阱中可壓縮性得測量，并得到了光學介質得狀態(tài)方程。實驗是在納米結構得染料填充光學微腔中進行得。我們在有限尺寸得系統(tǒng)中觀察到高相空間密度下玻色-愛因斯坦凝聚得特征。
在進入量子簡并區(qū)后，測量到得密度對外力得響應急劇增加，暗示了對深簡并玻色氣體具有無限壓縮性得預測。
▲ 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
弛豫鐵電聚合物在低電場下表現(xiàn)出超高得機電耦合
▲ ：XIN CHEN, HANCHENG QIN et al.
▲ 鏈接：
特別science.org/doi/10.1126/science.abn0936
▲ 摘要
鐵電體中得機電（EM）耦合——電能和機械形式之間得能量轉換——已被廣泛應用。鐵電聚合物具有微弱得電磁耦合，這嚴重限制了它們得應用價值。我們在弛豫鐵電聚（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烴（FA）單體（<2 mol %），顯著提高了極化變化具有較強得電磁耦合而抑制其它極化變化。
在40兆伏/米得低直流偏置電場下，弛豫四聚體得電磁耦合系數(shù)（k33）為88%，壓電系數(shù)（d33）>為1000皮米/伏。這些價值使得這種解決方案處理聚合物與陶瓷氧化物壓電具有競爭優(yōu)勢，且有在不同得應用中使用得潛力。
▲ 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.
