Compile the | Li Yan
Science, 21 JAN 2022, VOL 375, ISSUE 6578
Science, January 21, 2022, Vol. 375, No. 6578
Physics Physics
Attosecond coherent electron motion in Auger-Meitner decay
Atsecond coherent electron motion in Auger-Meitner decay
▲ 作者:SIQI LI, TARANDRIVER, PHILIPP ROSENBERGER, ELIO G. CHAMPENOIS et al.
▲ Link:
https://www.science.org/doi/10.1126/science.abj2096
▲ Abstract
In quantum systems, the coherent superposition of electron states evolves on ultrafast time scales (from a few femtoseconds to atelectrons; 1 atassecond = 0.001 femtosecond = 10−18 sec) towards time-dependent charge density. Here, we perform time-resolved measurements using atsecond soft X-ray pulses generated by free electron lasers to track the evolution of coherent nucleus-hole excitation in nitric oxide.
Using an additional circularly polarized infrared laser pulse, we created a clock for time-resolved electron dynamics and demonstrated controlling coherent electron motion by adjusting the photon energy of the X-ray pulse. The nuclear excited state provides a basic experimental platform for studying the coherent electron dynamics in highly excited states and strongly correlated substances.
▲ Abstract
In quantum systems, coherent superpositions of electronic states evolve on ultrafast time scales (few femtoseconds to attoseconds; 1 attosecond = 0.001 femtoseconds = 10−18 seconds), leading to a time-dependent charge density. Here we performed time-resolved measurements using attosecond soft x-ray pulses produced by a free-electron laser, to track the evolution of a coherent core-hole excitation in nitric oxide. Using an additional circularly polarized infrared laser pulse, we created a clock to time-resolve the electron dynamics and demonstrated control of the coherent electron motion by tuning the photon energy of the x-ray pulse. Core-excited states offer a fundamental test bed for studying coherent electron dynamics in highly excited and strongly correlated matter.
Materials Science
Conformal quantum dot–SnO2 layers as electron transporters for efficient perovskitesolar cells
The conformal quantum dot SnO2 layer acts as an electron transport layer for high-efficiency perovskite solar cells
▲ 作者:MINJIN KIM, XJAEKIJEONG, HAIZHOU LU, TAE KYUNG LEE et al.
https://www.science.org/doi/10.1126/science.abh1885
Improvements to perovskite solar cells (PSCs) are focused on improving their power conversion efficiency (PCE), operational stability, and maintaining high performance as they expand to module size. We reported a thin layer of polyacrylic acid (PAA) stabilized QD-SnO2 (paa-QD- SnO2), enhanced light absorption, and greatly inhibited non-radiative recombination on perovskite films.
The textured paa-QD-SnO2 double film brings the PCE to 25.7% (certified at 25.4%), and the corresponding PSC has high stability. THE PCEs of PSCs with an active area of 1, 20 and 64 square centimeters were 23.3, 21.7 and 20.6%, respectively.
Improvements to perovskite solar cells (PSCs) have focused on increasing their power conversion efficiency (PCE) and operational stability and maintaining high performance upon scale-up to module sizes. We report that replacing the commonly used mesoporous–titanium dioxide electron transport layer (ETL) with a thin layer of polyacrylic acid–stabilized tin(IV) oxide quantum dots (paa-QD-SnO2) on the compact–titanium dioxide enhanced light capture and largely suppressed nonradiative recombination at the ETL–perovskite interface. The use of paa-QD- SnO2 as electron-selective contact enabled PSCs (0.08 square centimeters) with a PCE of 25.7% (certified 25.4%) and high operational stability and facilitated the scale-up of the PSCs to larger areas. PCEs of 23.3, 21.7, and 20.6% were achieved for PSCs with active areas of 1, 20, and 64 square centimeters, respectively.
Three-dimensional direct lithography of stable perovskite nanocrystals in glass
Three-dimensional direct writing of stable perovskite nanocrystals in glass
▲ 作者：KE SUN, DEZHI TAN,XINYUAN FANG, XINTAO XIA et al.
https://www.science.org/doi/10.1126/science.abj2691
Material composition engineering and device fabrication of perovskite nanocrystals (PNCs) in solution introduce organic contamination and require multiple steps of synthesis, processing, and stabilization. We report three-dimensional direct writing of tunable components and band gap perovskite nanocrystals. Femtosecond laser-induced liquid phase nanophase separation technology is used to control the distribution of halide ions at the nanoscale.
PNCs have significant stability under ultraviolet irradiation, in organic solutions and at high temperatures (up to 250°C). 3D printed structures in glass are used for optical storage, miniature light-emitting diodes, and holographic displays. The PNC formation mechanism and composition tunables have been verified.
Material composition engineering and device fabrication of perovskite nanocrystals (PNCs) in solution can introduce organic contamination and entail several synthetic, processing, and stabilization steps. We report three-dimensional (3D) direct lithography of PNCs with tunable composition and bandgap in glass. The halide ion distribution was controlled at the nanoscale with ultrafast laser–induced liquid nanophase separation. The PNCs exhibit notable stability against ultraviolet irradiation, organic solution, and high temperatures (up to 250°C). Printed 3D structures in glass were used for optical storage, micro–light emitting diodes, and holographic displays. The proposed mechanisms of both PNC formation and composition tunability were verified.
Visualizing broken symmetry and topological defects in a quantum Hall ferromagnet
Visualization of symmetry breakage and topological defects in quantum Hall ferromagnets
▲ 作者:XIAOMENG LIU, GELAREHFARAHI, CHENG-LI CHIU, ZLATKO PAPIC, KENJI WATANABE et al.
https://www.science.org/doi/10.1126/science.abm3770
Under the action of a strong magnetic field, the interaction between electrons in graphene forms a rich set of spin or valley symmetrical quantum Hall ferromagnetic phases (QHFM). The trough order characteristics of graphene QHFM phases and the spectral characteristics of fractional-order quantum Hall phases were analyzed by visualizing the electron wave function at the atomic scale using scanning tunneling spectroscopy (STS).
Under charge neutrality, we observe a field-tuned continuous quantum phase transition from valley polarization to inter-valley coherence with Kekulé distortion of its electron density. Mapping the grain texture extracted from the STS measurement of the Kekulé phase, we can see the valley soliton excitation near the charged defect. Our techniques can be applied to study the valley sequence phases and their topological excitations in a variety of materials.
The interaction between electrons in graphene under high magnetic fields drives the formation of a rich set of quantum Hall ferromagnetic (QHFM) phases with broken spin or valley symmetry. Visualizing atomic-scale electronic wave functions with scanning tunneling spectroscopy (STS), we resolved microscopic signatures of valley ordering in QHFM phases and spectral features of fractional quantum Hall phases of graphene. At charge neutrality, we observed a field-tuned continuous quantum phase transition from a valley-polarized state to an intervalley coherent state, with a Kekulé distortion of its electronic density. Mapping the valley texture extracted from STS measurements of the Kekulé phase, we could visualize valley skyrmion excitations localized near charged defects. Our techniques can be applied to examine valley-ordered phases and their topological excitations in a wide range of materials.
Social Psychology Social Psychology
Early concepts of intimacy: Young humans use saliva sharing to infer close relationships
Early concept of intimacy: Infants and young children infer intimacy by sharing saliva
▲ 作者：ASHLEY J. THOMAS, XBRANDON WOO, DANIEL NETTLE et al.
https://www.science.org/doi/10.1126/science.abh1054
Throughout human society, people form "intimate" relationships characterized by strong attachments, obligations, and mutual responses. People in intimate relationships share food utensils, kisses, or have other special exchanges, including sharing saliva. We found from the behavior of children and infants that two people who share saliva (rather than other positive social interactions) have very different relationships.
Children want to share saliva in the nuclear family. Infants and young children believe that people who share saliva will respond to each other's pain. Parents have confirmed that sharing saliva is a valid clue to how close their children are in their social environment. The ability to use unique interactions to infer categories of relationships arises early in life without clear teaching; This enables young people to quickly identify intimate relationships inside and outside the home.
Across human societies, people form “thick” relationships characterized by strong attachments, obligations, and mutual responsiveness. People in thick relationships share food utensils, kiss, or engage in other distinctive interactions that involve sharing saliva. We found that children, toddlers, and infants infer that dyads who share saliva (as opposed to other positive social interactions) have a distinct relationship. Children expect saliva sharing to happen in nuclear families. Toddlers and infants expect that people who share saliva will respond to one another in distress. Parents confirm that saliva sharing is a valid cue of relationship thickness in their children’s social environments. The ability to use distinctive interactions to infer categories of relationships thus emerges early in life, without explicit teaching; this enables young humans to rapidly identify close relationships, both within and beyond families.
Geoscience for Earth Sciences
Protectingconnectivity promotes successful biodiversity and fisheries conservation
Protecting connectivity contributes to the successful conservation of biodiversity and fisheries
▲ いい:LUISA FONTOURA, STEPHANIED'AGATA, MAJAMBO GAMOYODIEGO R. BARNECHE et al.
https://www.science.org/doi/10.1126/science.abg4351
The decline in coral reefs around the world has led to calls for strategies to coordinate biodiversity conservation and fisheries interests. However, there are still considerable gaps in our understanding of the spatial ecology of ecosystem services. We combined spatial information from larval dispersal networks with estimates of human stress to test the importance of connectivity for ecosystem service delivery.
We combined spatial information from larval dispersal networks with estimates of human stress to test the importance of connectivity for ecosystem service delivery. We found that coral reefs that receive larvae from highly connected dispersed channels are associated with higher fish species richness. In general, larval "sinks" contain twice as much fish biomass as "sources" and, when protected, exhibit greater resilience to human stress.
Despite their potential to support biodiversity sustainability and sustainable fisheries, up to 70 per cent of important proliferation corridors, sinks and source reefs remain unprotected, underscoring the need to strengthen well-connected coral reef networks.
The global decline of coral reefs has led to calls for strategies that reconcile biodiversity conservation and fisheries benefits. Still, considerable gaps in our understanding of the spatial ecology of ecosystem services remain. We combined spatial information on larval dispersal networks and estimates of human pressure to test the importance of connectivity for ecosystem service provision. We found that reefs receiving larvae from highly connected dispersal corridors were associated with high fish species richness. Generally, larval “sinks” contained twice as much fish biomass as “sources” and exhibited greater resilience to human pressure when protected. Despite their potential to support biodiversity persistence and sustainable fisheries, up to 70% of important dispersal corridors, sinks, and source reefs remain unprotected, emphasizing the need for increased protection of networks of well-connected reefs.