Artificial microstructures,which allow us to control and change the properties of wave fields through changing the geometrical parameters and the arrangements of microstructures,have attracted plenty of attentions in ...Artificial microstructures,which allow us to control and change the properties of wave fields through changing the geometrical parameters and the arrangements of microstructures,have attracted plenty of attentions in the past few decades.Some artificial microstructure based research areas,such as metamaterials,metasurfaces and phononic topological insulators,have seen numerous novel applications and phenomena.The manipulation of different dimensions(phase,amplitude,frequency or polarization)of wave fields,particularly,can be easily achieved at subwavelength scales by metasurfaces.In this review,we focus on the recent developments of wave field manipulations based on artificial microstructures and classify some important applications from the viewpoint of different dimensional manipulations of wave fields.The development tendency of wave field manipulation from single-dimension to multidimensions provides a useful guide for researchers to realize miniaturized and integrated optical and acoustic devices.展开更多
Twisted bilayer graphene(TBG),which has drawn much attention in recent years,arises from van der Waals materials gathering each component together via van der Waals force.It is composed of two sheets of graphene rotat...Twisted bilayer graphene(TBG),which has drawn much attention in recent years,arises from van der Waals materials gathering each component together via van der Waals force.It is composed of two sheets of graphene rotated relatively to each other.Moirépotential,resulting from misorientation between layers,plays an essential role in determining the band structure of TBG,which directly relies on the twist angle.Once the twist angle approaches a certain critical value,flat bands will show up,indicating the suppression of kinetic energy,which significantly enhances the importance of Coulomb interaction between electrons.As a result,correlated states like correlated insulators emerge from TBG.Surprisingly,superconductivity in TBG is also reported in many experiments,which drags researchers into thinking about the underlying mechanism.Recently,the interest in the atomic reconstruction of TBG at small twist angles comes up and reinforces further understandings of properties of TBG.In addition,twisted multilayer graphene receives more and more attention,as they could likely outperform TBG although they are more difficult to handle experimentally.In this review,we mainly introduce theoretical and experimental progress on TBG.Besides the basic knowledge of TBG,we emphasize the essential role of atomic reconstruction in both experimental and theoretical investigations.The consideration of atomic reconstruction in small-twist situations can provide us with another aspect to have an insight into physical mechanism in TBG.In addition,we cover the recent hot topic,twisted multilayer graphene.While the bilayer situation can be relatively easy to resolve,multilayer situations can be really complicated,which could foster more unique and novel properties.Therefore,in the end of the review,we look forward to future development of twisted multilayer graphene.展开更多
基金This work was supported by the National Key Research and Development Program of China(2016YFA0301102 and 2017YFA0303800)the National Natural Science Fund for Distinguished Young Scholar(11925403)+2 种基金the National Natural Science Foundation of China(11974193,91856101,and 11774186)Natural Science Foundation of Tianjin for Distinguished Young Scientists(18JCJQJC45700)the China Postdoctoral Science Foundation(2020M680851).
文摘Artificial microstructures,which allow us to control and change the properties of wave fields through changing the geometrical parameters and the arrangements of microstructures,have attracted plenty of attentions in the past few decades.Some artificial microstructure based research areas,such as metamaterials,metasurfaces and phononic topological insulators,have seen numerous novel applications and phenomena.The manipulation of different dimensions(phase,amplitude,frequency or polarization)of wave fields,particularly,can be easily achieved at subwavelength scales by metasurfaces.In this review,we focus on the recent developments of wave field manipulations based on artificial microstructures and classify some important applications from the viewpoint of different dimensional manipulations of wave fields.The development tendency of wave field manipulation from single-dimension to multidimensions provides a useful guide for researchers to realize miniaturized and integrated optical and acoustic devices.
文摘Twisted bilayer graphene(TBG),which has drawn much attention in recent years,arises from van der Waals materials gathering each component together via van der Waals force.It is composed of two sheets of graphene rotated relatively to each other.Moirépotential,resulting from misorientation between layers,plays an essential role in determining the band structure of TBG,which directly relies on the twist angle.Once the twist angle approaches a certain critical value,flat bands will show up,indicating the suppression of kinetic energy,which significantly enhances the importance of Coulomb interaction between electrons.As a result,correlated states like correlated insulators emerge from TBG.Surprisingly,superconductivity in TBG is also reported in many experiments,which drags researchers into thinking about the underlying mechanism.Recently,the interest in the atomic reconstruction of TBG at small twist angles comes up and reinforces further understandings of properties of TBG.In addition,twisted multilayer graphene receives more and more attention,as they could likely outperform TBG although they are more difficult to handle experimentally.In this review,we mainly introduce theoretical and experimental progress on TBG.Besides the basic knowledge of TBG,we emphasize the essential role of atomic reconstruction in both experimental and theoretical investigations.The consideration of atomic reconstruction in small-twist situations can provide us with another aspect to have an insight into physical mechanism in TBG.In addition,we cover the recent hot topic,twisted multilayer graphene.While the bilayer situation can be relatively easy to resolve,multilayer situations can be really complicated,which could foster more unique and novel properties.Therefore,in the end of the review,we look forward to future development of twisted multilayer graphene.
