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Anomalous valley Hall effect in two-dimensional valleytronic materials
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作者 陈洪欣 原晓波 任俊峰 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第4期2-14,共13页
The anomalous valley Hall effect(AVHE)can be used to explore and utilize valley degrees of freedom in materials,which has potential applications in fields such as information storage,quantum computing and optoelectron... The anomalous valley Hall effect(AVHE)can be used to explore and utilize valley degrees of freedom in materials,which has potential applications in fields such as information storage,quantum computing and optoelectronics.AVHE exists in two-dimensional(2D)materials possessing valley polarization(VP),and such 2D materials usually belong to the hexagonal honeycomb lattice.Therefore,it is necessary to achieve valleytronic materials with VP that are more readily to be synthesized and applicated experimentally.In this topical review,we introduce recent developments on realizing VP as well as AVHE through different methods,i.e.,doping transition metal atoms,building ferrovalley heterostructures and searching for ferrovalley materials.Moreover,2D ferrovalley systems under external modulation are also discussed.2D valleytronic materials with AVHE demonstrate excellent performance and potential applications,which offer the possibility of realizing novel low-energy-consuming devices,facilitating further development of device technology,realizing miniaturization and enhancing functionality of them. 展开更多
关键词 anomalous valley Hall effect valley polarization valleytronics two-dimensional materials
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Progress on two-dimensional ferrovalley materials
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作者 李平 刘邦 +2 位作者 陈帅 张蔚曦 郭志新 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第1期32-43,共12页
The electron's charge and spin degrees of freedom are at the core of modern electronic devices. With the in-depth investigation of two-dimensional materials, another degree of freedom, valley, has also attracted t... The electron's charge and spin degrees of freedom are at the core of modern electronic devices. With the in-depth investigation of two-dimensional materials, another degree of freedom, valley, has also attracted tremendous research interest. The intrinsic spontaneous valley polarization in two-dimensional magnetic systems, ferrovalley material, provides convenience for detecting and modulating the valley. In this review, we first introduce the development of valleytronics.Then, the valley polarization forms by the p-, d-, and f-orbit that are discussed. Following, we discuss the investigation progress of modulating the valley polarization of two-dimensional ferrovalley materials by multiple physical fields, such as electric, stacking mode, strain, and interface. Finally, we look forward to the future developments of valleytronics. 展开更多
关键词 ferrovalley valley polarization two-dimensional materials multi-field tunable
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Recent progress on valley polarization and valley-polarized topological states in two-dimensional materials
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作者 王斐 张亚玲 +2 位作者 杨文佳 张会生 许小红 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第1期16-31,共16页
Valleytronics, using valley degree of freedom to encode, process, and store information, may find practical applications in low-power-consumption devices. Recent theoretical and experimental studies have demonstrated ... Valleytronics, using valley degree of freedom to encode, process, and store information, may find practical applications in low-power-consumption devices. Recent theoretical and experimental studies have demonstrated that twodimensional(2D) honeycomb lattice systems with inversion symmetry breaking, such as transition-metal dichalcogenides(TMDs), are ideal candidates for realizing valley polarization. In addition to the optical field, lifting the valley degeneracy of TMDs by introducing magnetism is an efficient way to manipulate the valley degree of freedom. In this paper, we first review the recent progress on valley polarization in various TMD-based systems, including magnetically doped TMDs,intrinsic TMDs with both inversion and time-reversal symmetry broken, and magnetic TMD heterostructures. When topologically nontrivial bands are empowered into valley-polarized systems, valley-polarized topological states, namely valleypolarized quantum anomalous Hall effect can be realized. Therefore, we have also reviewed the theoretical proposals for realizing valley-polarized topological states in 2D honeycomb lattices. Our paper can help readers quickly grasp the latest research developments in this field. 展开更多
关键词 valley polarization valley-polarized topological states two-dimensional material
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Valleytronic topological filters in silicene-like inner-edge systems
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作者 谢航 吕小龙 杨加恩 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第1期66-74,共9页
Inner edge state with spin and valley degrees of freedom is a promising candidate for designing a dissipationless device due to the topological protection. The central challenge for the application of the inner edge s... Inner edge state with spin and valley degrees of freedom is a promising candidate for designing a dissipationless device due to the topological protection. The central challenge for the application of the inner edge state is to generate and modulate the polarized currents. In this work, we discover a new mechanism to generate fully valley-and spin–valley-polarized current caused by the Bloch wavevector mismatch(BWM). Based on this mechanism, we design some serial-typed inner-edge filters. By using once of the BWM, the coincident states could be divided into transmitted and reflected modes, which can serve as a valley or spin–valley filter. In particular, while with twice of the BWM, the incident current is absolutely reflected to support an off state with a specified valley and spin, which is different from the gap effect.These findings give rise to a new platform for designing valleytronics and spin-valleytronics. 展开更多
关键词 topological insulator inner-edge state valley polarization spin polarization quantum transport
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The 2022 Extreme Heatwave in Shanghai,Lower Reaches of the Yangtze River Valley:Combined Influences of Multiscale Variabilities
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作者 Ping LIANG Zhiqi ZHANG +2 位作者 Yihui DING Zeng-Zhen HU Qi CHEN 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2024年第4期593-607,共15页
In the summer of 2022,China(especially the Yangtze River Valley,YRV)suffered its strongest heatwave(HW)event since 1961.In this study,we examined the influences of multiscale variabilities on the 2022 extreme HW in th... In the summer of 2022,China(especially the Yangtze River Valley,YRV)suffered its strongest heatwave(HW)event since 1961.In this study,we examined the influences of multiscale variabilities on the 2022 extreme HW in the lower reaches of the YRV,focusing on the city of Shanghai.We found that about 1/3 of the 2022 HW days in Shanghai can be attributed to the long-term warming trend of global warming.During mid-summer of 2022,an enhanced western Pacific subtropical high(WPSH)and anomalous double blockings over the Ural Mountains and Sea of Okhotsk,respectively,were associated with the persistently anomalous high pressure over the YRV,leading to the extreme HW.The Pacific Decadal Oscillation played a major role in the anomalous blocking pattern associated with the HW at the decadal time scale.Also,the positive phase of the Atlantic Multidecadal Oscillation may have contributed to regulating the formation of the double-blocking pattern.Anomalous warming of both the warm pool of the western Pacific and tropical North Atlantic at the interannual time scale may also have favored the persistency of the double blocking and the anomalously strong WPSH.At the subseasonal time scale,the anomalously frequent phases 2-5 of the canonical northward propagating variability of boreal summer intraseasonal oscillation associated with the anomalous propagation of a weak Madden-Julian Oscillation suppressed the convection over the YRV and also contributed to the HW.Therefore,the 2022 extreme HW originated from multiscale forcing including both the climate warming trend and air-sea interaction at multiple time scales. 展开更多
关键词 extreme heatwave multiscale variability air-sea interaction warming trend Yangtze River valley SHANGHAI
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Features of sampling stream sediments of large river valleys under cryolithogenesis conditions in the Balygychan-Sugoy trough,North-East of Russia
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作者 Artem S.Makshakov Raisa G.Kravtsova 《Acta Geochimica》 EI CAS CSCD 2024年第4期638-660,共23页
Comprehensive research has been implemented to raise the efficiency of the geochemical survey of stream sediments(SSs)that formed under the cryolithogenesis conditions.The authors analysed the composition,structure an... Comprehensive research has been implemented to raise the efficiency of the geochemical survey of stream sediments(SSs)that formed under the cryolithogenesis conditions.The authors analysed the composition,structure and specific features of the formation of exogenous anomalous geochemical fields(AGFs)identified through SSs of large river valleys of IV order.In our case,these were the valleys of Maly Ken,Ken and Tap Rivers.These rivers are located in the central and southern parts of the Balygychan-Sugoy trough enclosed in the Magadan region,North-East of Russia.The authors proposed a new technique to sample loose alluvium of SSs in the large river valleys along the profiles.The profiles were located across the valleys.The AGFs of Au,Ag,Pb,Zn,Sn,Bi,Mo and W were studied.Correlations between elements have been established.These elements are the main indicator elements of Au-Ag,Ag-Pb,Sn-Ag,Mo-W and Sn-W mineralization occurring on the sites under study.The results obtained were compared with the results of geochemical surveys of SSs.It is concluded that the AGFs recognized along the profiles reflect the composition and structure of eroded and drained ore zones,uncover completely and precisely the pattern of element distribution in loose sediments of large water flows.The alluvium fraction<0.25 mm seems to be most significant in a practical sense,as it concentrated numerous ore elements.Sampling of this fraction in the river valleys of IV order does not cause any difficulty,for this kind of material is plentiful.The developed technique of alluvium sampling within large river valleys is efficient in searching for diverse mineralization at all stages of prognostic prospecting.It is applicable for geochemical survey of SSs performed at different scales both in the North-East of Russia,as well as other regions with similar climatic conditions,where the SSs are formed under the cryolithogenesis conditions. 展开更多
关键词 Stream sediments Large river valleys Geochemical fields MINERALIZATION Indicator elements Geochemical survey
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Fully spin-polarized, valley-polarized and spin-valley-polarized electron beam splitters utilizing zero-line modes in a three-terminal device
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作者 吕小龙 杨加恩 谢航 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第6期596-603,共8页
Topological zero-line modes(ZLMs) with spin and valley degrees of freedom give rise to spin, valley and spinvalley transport, which support a platform for exploring quantum transport physics and potential applications... Topological zero-line modes(ZLMs) with spin and valley degrees of freedom give rise to spin, valley and spinvalley transport, which support a platform for exploring quantum transport physics and potential applications in spintronic/valleytronic devices. In this work, we investigate the beam-splitting behaviors of the charge current due to the ZLMs in a three-terminal system. We show that with certain combinations of ZLMs, the incident charge current along the interface between different topological phases can be divided into different polarized currents with unit transmittance in two outgoing terminals. As a result, fully spin-polarized, valley-polarized and spin-valley-polarized electron beam splitters are generated. The mechanism of these splitters is attributed to the cooperative effects of the distribution of the ZLMs and the intervalley and intravalley scatterings that are modulated by the wave-vector mismatch and group velocity mismatch. Interestingly, half-quantized transmittance of these scatterings is found in a fully spin-valley-polarized electron beam splitter.Furthermore, the results indicate that these splitters can be applicable to graphene, silicene, germanene and stanene due to their robustness against the spin–orbit coupling. Our findings offer a new way to understand the transport mechanism and investigate the promising applications of ZLMs. 展开更多
关键词 topological zero-line modes spin polarization valley polarization quantum transport
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Topological edge and corner states of valley photonic crystals with zipper-like boundary conditions
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作者 沈云峰 许孝芳 +2 位作者 孙铭 周文佶 常雅箐 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第4期480-491,共12页
We present a stable valley photonic crystal(VPC)unit cell with C_(3v)symmetric quasi-ring-shaped dielectric columns and realize its topological phase transition by breaking mirror symmetry.Based on this unit cell stru... We present a stable valley photonic crystal(VPC)unit cell with C_(3v)symmetric quasi-ring-shaped dielectric columns and realize its topological phase transition by breaking mirror symmetry.Based on this unit cell structure,topological edge states(TESs)and topological corner states(TCSs)are realized.We obtain a new type of wave transmission mode based on photonic crystal zipper-like boundaries and apply it to a beam splitter assembled from rectangular photonic crystals(PCs).The constructed beam splitter structure is compact and possesses frequency separation functions.In addition,we construct a box-shaped triangular PC structures with zipper-like boundaries and discover phenomena of TCSs in the corners,comparing its corner states with those formed by other boundaries.Based on this,we explore the regularities of the electric field patterns of TESs and TCSs,explain the connection between the characteristic frequencies and locality of TCSs,which helps better control photons and ensures low power consumption of the system. 展开更多
关键词 valley photonic crystal topological edge states topological corner states higher-order topological insulators topological phase transition
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Valley transport in Kekulé structures of graphene
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作者 王娟娟 汪军 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第1期44-53,共10页
Valleytronics is an emergent discipline in condensed matter physics and offers a new way to encode and manipulate information based on the valley degree of freedom in materials. Among the various materials being studi... Valleytronics is an emergent discipline in condensed matter physics and offers a new way to encode and manipulate information based on the valley degree of freedom in materials. Among the various materials being studied, Kekulé distorted graphene has emerged as a promising material for valleytronics applications. Graphene can be artificially distorted to form the Kekulé structures rendering the valley-related interaction. In this work, we review the recent progress of research on Kekulé structures of graphene and focus on the modified electronic bands due to different Kekulé distortions as well as their effects on the transport properties of electrons. We systematically discuss how the valley-related interaction in the Kekulé structures was used to control and affect the valley transport including the valley generation, manipulation, and detection. This article summarizes the current challenges and prospects for further research on Kekulé distorted graphene and its potential applications in valleytronics. 展开更多
关键词 GRAPHENE Y-shaped Kekulé(Y-Kek)lattice distortion structure O-Kekulé(O-Kek)structure valley current
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Protectivity of Freeze Dried Inactivated Rift Valley Fever Vaccine
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作者 Diana M. Abulmagd Mohamed Hassan Atwa +2 位作者 Noha Ezz Aldin Marwa Yehia Hammad Taradi Abdel Fattah Said 《Open Journal of Veterinary Medicine》 CAS 2024年第2期21-37,共17页
Background: Vaccinations for animals are crucial for food production, animal welfare, public health, and animal health. They are an affordable way to stop animal sickness, increase food production efficiency, and less... Background: Vaccinations for animals are crucial for food production, animal welfare, public health, and animal health. They are an affordable way to stop animal sickness, increase food production efficiency, and lessen or stop the spread of zoonotic diseases to humans. Animal vaccines that are both safe and efficacious are vital to modern culture. The vaccine should induce a strong, protective and prolonged immune response against the antigenic factor. In order to achieve these goals, novel vaccination techniques and an efficient adjuvant are required to render the vaccine immunogenically protective and trigger a strong immune response. Aim: Our study aims to promote and enhance the immunogenicity against RVF virus disease through lyophilized inactivated RVF vaccine through induction of early cellular, high and prolonged humeral immunity in vaccinated animals using cabopol as stabilizer and Saponin or normal saline as a diluent at time of vaccination. Moreover, manufacturing of these vaccines is easy to be done. Results: The gained results revealed that RVF freeze-dried vaccine with Carbopol that reconstituted using Saponin elicited better immune response than that reconstituted using normal saline (NaCl). The cell mediated immune response as represented by lymphocyte blastogenesis and phagocytic activity were markedly increased with high levels when we used Saponin as a diluent than that in group vaccinated with vaccine diluted with NaCl, on the other side the humeral immune response in group vaccinated using the Saponin as diluent is more detected and stayed within the protective level till the end of 11<sup>th</sup> month post vaccination (1.5 TCID<sub>50</sub>) while the immune response induced after using normal saline as a diluent stayed within the protective level till the end of 10<sup>th</sup> month post vaccination (1.8 TCID<sub>50</sub>). Conclusion: The use of Saponin as a diluent for reconstitution of the freeze dried RVF vaccine is preferable than the use of normal saline enhancing both sheep cellular and humeral immune response. 展开更多
关键词 Rift valley Fever SAPONIN Cabopol Binary Ethylenemine Serum Neutralization Test
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Using a New Glacial History Paradigm and Bald Eagle Through Valley Topographic Map Evidence to Determine Central Pennsylvania’s Geomorphic History, USA
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作者 Eric Clausen 《Open Journal of Geology》 CAS 2024年第9期880-899,共20页
A new glacial history paradigm that describes huge and prolonged southwest-oriented meltwater floods flowing along the rising rim of a deep “hole” (which a large continental icesheet created and occupied) is used to... A new glacial history paradigm that describes huge and prolonged southwest-oriented meltwater floods flowing along the rising rim of a deep “hole” (which a large continental icesheet created and occupied) is used to explain previously unexplained or poorly explained central Pennsylvania Bald Eagle through valley region topographic map evidence. Pennsylvania’s Bald Eagle through valley as defined here extends in a northeast direction from near Altoona to near Williamsport along the Allegheny Front escarpment base and forms the boundary between the Appalachian Plateau to the northwest and the Ridge and Valley Province to the southeast. The Lycoming and Towanda Creek valleys follow a probable northeastern Bald Eagle through valley extension and a probable southern extension continues southward along the Allegheny Front base by crossing Juniata River tributary drainage basins to reach the Potomac River drainage basin. Landform features identified on topographic maps, which include through valleys (valleys crossing drainage divides), barbed tributaries, drainage route orientations, drainage route direction changes, water gaps, and gaps located along the Allegheny Front crest, are used to reconstruct how the Pennsylvania Susquehanna and Juniata River drainage systems developed. The resulting geomorphic history describes how massive southwest-oriented floods moving across what was probably a low relief and rising surface (now preserved if preserved at all by the region’s highest elevations) flowed to an actively eroding Potomac River drainage system before being captured and sometimes reversed first by Juniata River valley headward erosion, second by West Branch Susquehanna River valley headward erosion (to create northeast-oriented Bald Eagle Creek and the northeast-oriented West Branch Susquehanna River segment) and third by North Branch Susquehanna River valley headward erosion. This interpretation explains most if not all of the previously poorly explained and unexplained topographic map evidence. 展开更多
关键词 Allegheny Front Appalachian Plateau Barbed Tributaries Juniata River Susquehanna River Ridge and valley Province
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Integrated Development of Tea and Tourism in Taishan Mountain Tea Valley in the Context of Rural Revitalization
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作者 Dongmei ZHANG Mengzhen SONG 《Asian Agricultural Research》 2024年第1期1-9,共9页
In recent years,the integrated development of the tea and tourism has become an important way to promote the rural revitalization of Tai'an tea-producing areas,but the state of industrial upgrading still needs to ... In recent years,the integrated development of the tea and tourism has become an important way to promote the rural revitalization of Tai'an tea-producing areas,but the state of industrial upgrading still needs to be improved.In order to better integrate tea and tourism in Tea Valley,this paper uses questionnaire and SWOT analysis to study.It found the following problems:(i)45.7%of tourists were interested in tea culture,but they know litle about it,and the integration of tea culture and tea tourism products is low.(i)50.54%of the tourists were interested in the tea picking experience project and wanted to add the tea food experience item.(ii)The acceptance of 45.7%of tourists to scenic spots was 1-2 h,which shows that the quality of transportation service facilities and personnel needs to be improved.Combined with the SWOT analysis,it is found that the scenic spot is rich in resources,convenient transportation,profound cultural heritage,and good govern-ment policy support conditions,which is suitable for the SO strategy(growth development strategy),so the scenic spot relies on internal ad-vantages and seizes external opportunities to develop the integration of tea and tourism.Based on the analysis results,it came up with the perti-nent recommendations for the key problems:(i)The infrastructure service is not well established.It is suggested that scenic spots should in-crease investment,regularly train service personnel to improve their quality,and improve transportation services,accommodation,catering and public service hardware facilities.(i)Tea tourism products are insufficient.It is suggested that tea tourism products should be innovatively designed and tea tourism experiential products and tourism commodities should be planned.(i)Tea culture and tourism lack organic combi-nation.It is recommended to deeply excavate tea culture,and take consideration of both spiritual and material aspects.The specific methods include building teahouses,Taishan Mountain(Mount Tai)tea culture throughout the whole process of tea production,development and pro-cessing,and AR tea culture experience hall can be built to make tourists feel tea culture from dfferent perspectives.(iv)The publicity is in-sufficient.Strategies should be made in three aspects:improving the Internet media,taking into account the traditional media,and expanding the market based on the surrounding areas.(v)The tea industry chain is short.It is recommended to add four new industrial chain designs of"tea+accommodation,tea+catering,tea+Intemet,tea+training",hoping to bring some inspiration and ideas to the managers of scenic spots. 展开更多
关键词 Integrated development of tea and tourism Tai'an Tea valley Problems Countermeasures and recommendations
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Temporal, Spatial, and Hypsometrical Dispersion of Nutrients in the Hula Valley, Israel
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作者 Moshe Gophen Valerie Orlov-Levin 《Open Journal of Ecology》 2024年第8期604-628,共25页
Until 1957 most of the Hula Valley was occupied by swampy wetland covered by dense vegetation and old Lake Hula. Organic matter was accumulated in the bottom, decomposed under anoxic conditions creating Peat material.... Until 1957 most of the Hula Valley was occupied by swampy wetland covered by dense vegetation and old Lake Hula. Organic matter was accumulated in the bottom, decomposed under anoxic conditions creating Peat material. The wetland and the old lake were drained and the land-use was converted into agricultural development. Nutrients migrations from the Hula Valley through the headwater discharges carrying nutrients, where nitrogen enhancement is critical, significantly affecting water quality in down-stream Lake Kinneret. The fate of the Hula originated nutrients is partly known whilst fate of the others which might be probably a threat on the Kinneret water quality is unknown. The hypsometrical and spatial distribution of the Hula Valley originated nutrients within three depths level was indicated: shallowest level of surface water, intermediate level of underground water table and the deepest level of Lignite waters. The Hypsometrical and spatial distribution and regional origin of the nutrient in the Hula Valley was defined. Organic Nitrogen, Sulfate and Nitrates are mostly Hula Valley originated nutrients whilst most of the Phosphorus externally contributed to Lake Kinneret originate outside the Hula Valley. An underground north-south Hydrological gradient and nutrient migration along was indicated. It is suggested that an underground plastic barrier do not totally prevent horizontal nutrient migration. Hypsometrical downward migrated nutrients probably accumulate within the “Lignite” depth level. Management policy of increasing Peat Soil moisture, is recommended. 展开更多
关键词 Hula valley Kinneret NUTRIENTS RUNOFF UNDERGROUND LIGNITE
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Salinization-Desalinization (SDS) Processes—A Linkage between Hula Valley and Lake Kinneret Ecosystem Management
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作者 Moshe Gophen 《Open Journal of Ecology》 2024年第9期731-746,共16页
The salinization process resulted in agricultural damage in the Hula Valley and water quality deterioration in Lake Kinneret. Therefore, salinization-desalinization (SDS) processes have been emphasized in the last two... The salinization process resulted in agricultural damage in the Hula Valley and water quality deterioration in Lake Kinneret. Therefore, salinization-desalinization (SDS) processes have been emphasized in the last two decades. Global and regional extreme climatological events and water scarcity strengthen the link between Hula Valley and Lake Kinneret management design. A bond between optimizing Hula agricultural maintenance and Kinneret water quality protection is conclusively suggested. Saline contribution originated from the southern Hula Valley region to the underground and surface water is higher than from the northern organic soil. The impact of eastern water Intrusion from the Golan Heights as surface waters, river discharge and underground seepage into the Hula Valley represent north-south gradient enhancement. Salinized surface water contribution from the Hula Valley to Lake Kinneret is unwanted because presently Kinneret desalinization management policy is critically required. The present salinization of surface and underground water in the Hula Valley indicates the upper limit suitable for agricultural crop optimization and the decline of salinity is crucial. Enhancement of the portion of Jordan water within the total balance in the valley is beneficial for Hula agricultural crops but serves as a disadvantage to Kinneret desalinization implementation. Therefore, the enhancement of lake water exchange is recommended. 展开更多
关键词 Hula valley Lake Kinneret SALINIZATION Desalinization
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Flood Risk Assessment in the Lower Valley of Ouémé, Benin
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作者 Yaovi Aymar Bossa Octave Djangni +3 位作者 Yacouba Yira Jean Hounkpè Angèle D. Avossè Luc Ollivier Sintondji 《Open Journal of Modern Hydrology》 CAS 2024年第2期130-151,共22页
In response to the increased frequency of flood events in recent years, it has become crucial to enhance preparedness and anticipation through precise flood risk assessments. To this end, this study aims to produce up... In response to the increased frequency of flood events in recent years, it has become crucial to enhance preparedness and anticipation through precise flood risk assessments. To this end, this study aims to produce updated and precise flood risk maps for the Lower Valley of Ouémé River Basin, located in the South of Benin. The methodology used consisted of a combination of geographical information systems (GIS) and multi-criteria analysis, including Analytical Hierarchy Process (AHP) methods to define and quantify criteria for flood risk assessment. Seven hydro-geomorphological indicators (elevation, rainfall, slope, distance from rivers, flow accumulation, soil type, and drainage density), four socio-economic vulnerability indicators (female population density, literacy rate, poverty index, and road network density), and two exposure indicators (population density and land use) were integrated to generate risk maps. The results indicate that approximately 21.5% of the Lower Valley is under high and very high flood risk, mainly in the south between Dangbo, So-Ava, and Aguégués. The study findings align with the historical flood pattern in the region, which confirms the suitability of the used method. The novelty of this work lies in its comprehensive approach, the incorporation of AHP for weighting factors, and the use of remote sensing data, GIS technology, and spatial analysis techniques which adds precision to the mapping process. This work advances the scientific understanding of flood risk assessment and offers practical insights and solutions for flood-prone regions. The detailed flood risk indicator maps obtained stand out from previous studies and provide valuable information for effective flood risk management and mitigation efforts in the Lower Valley of Ouémé. 展开更多
关键词 Flood Hazard Exposure VULNERABILITY Risk Lower valley of Ouémé
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Hydrogeochemical Characterization of Aquifer Systems and Surface Water/Groundwater Relations in the Lower Senegal River Valley
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作者 Abibatou Camara Fatou Diop Ngom +2 位作者 Moctar Diaw Cheikh Tidiane Wade Ibrahima Mall 《Journal of Geoscience and Environment Protection》 2024年第6期232-254,共23页
This study assesses the chemical quality of water resources in the Lower Senegal River valley, based on 35 samples collected in November 2022. Major ion concentrations in surface water and groundwater were analyzed us... This study assesses the chemical quality of water resources in the Lower Senegal River valley, based on 35 samples collected in November 2022. Major ion concentrations in surface water and groundwater were analyzed using classical geochemical interpretation diagrams (Piper, GIBBS, etc.) and multivariate geostatistical analyses, including hierarchical cluster analysis (HCA) and principal component analysis (PCA). The results revealed three types of facies: Ca-Mg-HCO3-type facies, characteristic of poorly mineralized waters such as surface waters and groundwater from dune formations and the alluvial plain close to the hydraulic axis;Na-Cl type facies associated with well waters located in the alluvial plain that tap Inchirian or Nouakchottian shallow reservoirs and Maastrichtian deep borehole waters;and mixed Ca-Cl and Na-HCO3 type facies observed in certain floodplain and dune reservoirs. The results showed a strong correlation between sodium, chlorides, bromides, and electrical conductivity, indicating a significant contribution of these ions to groundwater mineralization. The various sources of water mineralization include mixing processes between surface water or rainwater, or calcite or dolomite dissolution processes (for weakly mineralized waters), basic exchanges or inverse basic exchanges between the aquifer and the water table (for moderately mineralized waters), and evaporation processes, halite dissolution, and paleosalinity during periods of marine transgression and regression (for highly mineralized waters). The study also highlighted the high vulnerability of the alluvial aquifer to pollution from intensive irrigated agriculture, as significant quantities of sulfates and nitrates were measured in some samples. These results also highlight the importance of water quality management in the Lower Senegal Valley, particularly as concerns the protection of the alluvial aquifer against pollution from irrigated agriculture. 展开更多
关键词 Senegal River valley GROUNDWATER POLLUTION Agriculture Alluvial Aquifer
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Design of sign-reversible Berry phase effect in 2D magneto-valley material
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作者 韩曰通 杨宇贤 +1 位作者 李萍 张昌文 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第9期400-407,共8页
Manipulating sign-reversible Berry phase effects is both fundamentally intriguing and practically appealing for searching for exotic topological quantum states.However,the realization of multiple Berry phases in the m... Manipulating sign-reversible Berry phase effects is both fundamentally intriguing and practically appealing for searching for exotic topological quantum states.However,the realization of multiple Berry phases in the magneto-valley lattice is rather challenging due to the complex interactions from spin-orbit coupling(SOC),band topology,and magnetic ordering.Here,taking single-layer spin-valley RuCl_(2)as an example,we find that sign-reversible Berry phase transitions from ferrovalley(FV)to half-valley semimetal(HVS)to quantum anomalous valley Hall effect(QAVHE)can be achieved via tuning electronic correlation effect or biaxial strains.Remarkably,QAVHE phase,which combines both the features of quantum anomalous Hall and anomalous Hall valley effect,is introduced by sign-reversible Berry curvature or band inversion of d_(xy)/d_(x^(2)-y^(2))and d_(z^(2))orbitals at only one of the K/K′valleys of single-layer RuCl_(2).And the boundary of QAVHE phase is the HVS state,which can achieve 100%intrinsically valley polarization.Further,a k·p model unveiled the valleycontrollable sign-reversible Berry phase effects.These discoveries establish RuCl_(2)as a promising candidate to explore exotic quantum states at the confluence of nontrivial topology,electronic correlation,and valley degree of freedom. 展开更多
关键词 valley polarization topological phase transition half-valley semimetal quantum anomalous valley Hall effect first-principles calculations
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Gate tunable spatial accumulation of valley-spin in chemical vapor deposition grown 40°-twisted bilayer WS2
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作者 Siwen Zhao Gonglei Shao +2 位作者 Zheng Vitto Han Song Liu Tongyao Zhang 《Journal of Semiconductors》 EI CAS CSCD 2023年第1期74-78,共5页
The emerging two-dimensional materials,particularly transition metal dichalcogenides(TMDs),are known to exhibit valley degree of freedom with long valley lifetime,which hold great promises in the implementation of val... The emerging two-dimensional materials,particularly transition metal dichalcogenides(TMDs),are known to exhibit valley degree of freedom with long valley lifetime,which hold great promises in the implementation of valleytronic devices.Especially,light-valley interactions have attracted attentions in these systems,as the electrical generation of valley magnetization can be readily achieved—a rather different route toward magnetoelectric(ME)effect as compared to that from conventional electron spins.However,so far,the moiré patterns constructed with twisted bilayer TMDs remain largely unexplored in regard of their valley spin polarizations,even though the symmetry might be distinct from the AB stacked bilayer TMDs.Here,we study the valley Hall effect(VHE)in 40°-twisted chemical vapor deposition(CVD)grown WS2moiré transistors,using optical Kerr rotation measurements at 20 K.We observe a clear gate tunable spatial distribution of the valley carrier imbalance induced by the VHE when a current is exerted in the system. 展开更多
关键词 transition metal dichalcogenides valleytronic devices light-valley interactions valley Hall effect
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Perspectives of spin-valley locking devices
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作者 陶玲玲 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第10期15-21,共7页
Valleytronics is an emerging field of research which utilizes the valley degree of freedom to encode information.However,it is technically nontrivial to produce a stable valley polarization and to achieve efficient co... Valleytronics is an emerging field of research which utilizes the valley degree of freedom to encode information.However,it is technically nontrivial to produce a stable valley polarization and to achieve efficient control and manipulation of valleys.Spin–valley locking refers to the coupling between spin and valley degrees of freedom in the materials with large spin–orbit coupling(SOC)and enables the manipulation of valleys indirectly through controlling spins.Here,we review the recent advances in spin–valley locking physics and outline possible device implications.In particular,we focus on the spin–valley locking induced by SOC and external electric field in certain two-dimensional materials with inversion symmetry and demonstrate the intriguing switchable valley–spin polarization,which can be utilized to design the promising electronic devices,namely,valley-spin valves and logic gates. 展开更多
关键词 spin–valley locking SPINTRONICS valleytronics spin–orbit coupling
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Single-layer intrinsic 2H-phase LuX_(2)(X=Cl,Br,I)with large valley polarization and anomalous valley Hall effect
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作者 胡春生 仵允京 +4 位作者 刘元硕 傅帅 崔晓宁 王易昊 张昌文 《Chinese Physics B》 SCIE EI CAS CSCD 2023年第3期478-483,共6页
Manipulation of the valley degree of freedom provides a new path for quantum information technology,but the real intrinsic large valley-polarization materials are rarely reported up to date.Here,we perform first-princ... Manipulation of the valley degree of freedom provides a new path for quantum information technology,but the real intrinsic large valley-polarization materials are rarely reported up to date.Here,we perform first-principles calculations to predict a class of 2H-phase single layer(SL)materials LuX_(2)(X=Cl,Br,I)to be ideal candidates.SL-Lu X_(2)are ferrovalley materials with a giant valley-polarization of 55 meV–148 meV as a result of its large spin–orbital coupling(SOC)and intrinsic ferromagnetism(FM).The magnetic transition temperatures of SL-LuI_(2)and SL-LuCl2are estimated to be 89 K–124 K,with a sizable magnetic anisotropy at out-of-plane direction.Remarkably,the anomalous valley Hall effect(AVHE)can be controlled in SL-LuX_(2)when an external electric field is applied.Moreover,the intrinsic valleypolarization of SL-LuI_(2)is highly robust for biaxial strain.These findings provide a promising ferrovalley material system for the experimentation of valleytronics and subsequent applications. 展开更多
关键词 intrinsic ferrovalley anomalous valley Hall effect first-principles calculations
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