Systems hosting flat bands offer a powerful platform for exploring strong correlation physics.Theoretically,topological degeneracy arising in systems with non-trivial topological orders on periodic manifolds of non-ze...Systems hosting flat bands offer a powerful platform for exploring strong correlation physics.Theoretically,topological degeneracy arising in systems with non-trivial topological orders on periodic manifolds of non-zero genus can generate ideal flat bands.However,experimental realization of such geometrically engineered systems is very difficult.In this work,we demonstrate that flat planes with strategically patterned hole defects can engineer ideal flat bands.We construct two families of models:singular flat band systems where degeneracy is stabilized by non-contractible loop excitations tied to hole defects and perfectly nested van Hove systems where degeneracy arises from line excitations in momentum space.These models circumvent the need for exotic manifolds while retaining the essential features of topological flat bands.By directly linking defect engineering to degeneracy mechanisms,our results establish a scalable framework for experimentally accessible flat band design.展开更多
The change in Egypt is a result of three factors:the autocratic rule of the Mubarak regime being challenged by globalization;the imbalance between economic growth and social development which created severe unemployme...The change in Egypt is a result of three factors:the autocratic rule of the Mubarak regime being challenged by globalization;the imbalance between economic growth and social development which created severe unemployment and poverty problems,worsened by imported inflation resulting from the global financial crisis;and,the pro-US and pro-Israel foreign policy pursued by the Mubarak regime which caused resentment among the Egyptian people and stimulated protests.To realize the socioeconomic development,establish a comprehensive development model,and create a stable and sustainable political structure will be formidable tasks for Egyptians in the post-Mubarak era.Thus,change will be a long-run process.Egypt would implement a more independent and neutral foreign policy,and will form with some other countries like Turkey a third group,i.e.a group in the middle.A new strategic structure in the Middle East would emerge through the change,with pro-US group,anti-US group,and a group in the middle as three main groups,based on competition between the Iranian model and the Turkish model,and US hegemonic power in the region would be weakened correspondingly.展开更多
基金supported by the Ministry of Science and Technology(Grant No.2022YFA1403901)the National Natural Science Foundation of China(Grant Nos.12494594,11888101,12174428,and 12504192)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB28000000)the New Cornerstone Investigator Program,the Chinese Academy of Sciences through the Youth Innovation Promotion Association(Grant No.2022YSBR-048)the Shanghai Science and Technology Innovation Action Plan(Grant No.24LZ1400800).
文摘Systems hosting flat bands offer a powerful platform for exploring strong correlation physics.Theoretically,topological degeneracy arising in systems with non-trivial topological orders on periodic manifolds of non-zero genus can generate ideal flat bands.However,experimental realization of such geometrically engineered systems is very difficult.In this work,we demonstrate that flat planes with strategically patterned hole defects can engineer ideal flat bands.We construct two families of models:singular flat band systems where degeneracy is stabilized by non-contractible loop excitations tied to hole defects and perfectly nested van Hove systems where degeneracy arises from line excitations in momentum space.These models circumvent the need for exotic manifolds while retaining the essential features of topological flat bands.By directly linking defect engineering to degeneracy mechanisms,our results establish a scalable framework for experimentally accessible flat band design.
文摘The change in Egypt is a result of three factors:the autocratic rule of the Mubarak regime being challenged by globalization;the imbalance between economic growth and social development which created severe unemployment and poverty problems,worsened by imported inflation resulting from the global financial crisis;and,the pro-US and pro-Israel foreign policy pursued by the Mubarak regime which caused resentment among the Egyptian people and stimulated protests.To realize the socioeconomic development,establish a comprehensive development model,and create a stable and sustainable political structure will be formidable tasks for Egyptians in the post-Mubarak era.Thus,change will be a long-run process.Egypt would implement a more independent and neutral foreign policy,and will form with some other countries like Turkey a third group,i.e.a group in the middle.A new strategic structure in the Middle East would emerge through the change,with pro-US group,anti-US group,and a group in the middle as three main groups,based on competition between the Iranian model and the Turkish model,and US hegemonic power in the region would be weakened correspondingly.
