Two-dimensional(2D)melting is a fundamental research topic in condensed matter physics,which can also provide guidance on fabricating new functional materials.Nevertheless,our understanding of 2D melting is still far ...Two-dimensional(2D)melting is a fundamental research topic in condensed matter physics,which can also provide guidance on fabricating new functional materials.Nevertheless,our understanding of 2D melting is still far from being complete due to existence of possible complicate transition mechanisms and absence of effective analysis methods.Here,using Monte Carlo simulations,we investigate 2D melting of 60°rhombs which melt from two different surface-fullycoverable crystals,a complex hexagonal crystal(cHX)whose primitive cell contains three rhombs,and a simple rhombic crystal(RB)whose primitive cell contains one rhomb.The melting of both crystals shows a sequence of solid,hexatic in molecular orientation(Hmo),and isotropic phases which obey the Berezinskii-Kosterlitz-Thouless-Halperin-Nelson-Young(BKTHNY)theory.However,local polymorphic configuration(LPC)based analysis reveals different melting mechanisms:the cHX-Hmotransition is driven by the proliferation of point-like defects during which defect-associated LPCs are generated sequentially,whereas the RB-Hmotransition is driven by line defects where defect-associated LPCs are generated simultaneously.These differences result in the observed different solid-Hmotransition points which areφA=0.812 for the cHX-HmoandφA=0.828 for the RB-Hmo.Our work will shed light on the initial-crystal-dependence of 2D melting behavior.展开更多
One-dimensional(1D)one-way waveguides based on topological edge states of two-dimensional(2D)gyromagnetic photonic crystals have been studied extensively.Here,we theoretically propose a three-dimensional(3D)all-dielec...One-dimensional(1D)one-way waveguides based on topological edge states of two-dimensional(2D)gyromagnetic photonic crystals have been studied extensively.Here,we theoretically propose a three-dimensional(3D)all-dielectric gyromagnetic photonic crystal with type-Ⅱ Weyl points.Based on the inclined band properties of the type-Ⅱ Weyl surface states,we design a 2D one-way interface transmission channel on the Weyl crystal.Light waves in such 2D waveguides can be transmitted robustly over metal obstacles almost without any back-reflection,topologically protected by the type-Ⅱ Weyl points.By manipulating the magnetic field or structural parameters,we also achieve the topological phase transition between Weyl phase and 3D Chern insulator phase and obtain the corresponding phase diagram,which provides more possibilities for topological regulation of the surface states.This work suggests a new way to construct unidirectional 2D waveguides with larger area of energy transmission in 3D space,which is a promising platform for developing 3D topological photonic devices.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11874277,21621004,12104453,and 12090054)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB33030300)
文摘Two-dimensional(2D)melting is a fundamental research topic in condensed matter physics,which can also provide guidance on fabricating new functional materials.Nevertheless,our understanding of 2D melting is still far from being complete due to existence of possible complicate transition mechanisms and absence of effective analysis methods.Here,using Monte Carlo simulations,we investigate 2D melting of 60°rhombs which melt from two different surface-fullycoverable crystals,a complex hexagonal crystal(cHX)whose primitive cell contains three rhombs,and a simple rhombic crystal(RB)whose primitive cell contains one rhomb.The melting of both crystals shows a sequence of solid,hexatic in molecular orientation(Hmo),and isotropic phases which obey the Berezinskii-Kosterlitz-Thouless-Halperin-Nelson-Young(BKTHNY)theory.However,local polymorphic configuration(LPC)based analysis reveals different melting mechanisms:the cHX-Hmotransition is driven by the proliferation of point-like defects during which defect-associated LPCs are generated sequentially,whereas the RB-Hmotransition is driven by line defects where defect-associated LPCs are generated simultaneously.These differences result in the observed different solid-Hmotransition points which areφA=0.812 for the cHX-HmoandφA=0.828 for the RB-Hmo.Our work will shed light on the initial-crystal-dependence of 2D melting behavior.
基金supported by the National Natural Science Foundation of China(Grant No.11974119)Science and Technology Project of Guangdong(Grant No.2020B010190001)+1 种基金Guangdong Innovative and Entrepreneurial Research Team Program(Grant No.2016ZT06C594)National Key R&D Program of China(Grant No.2018YFA0306200)。
文摘One-dimensional(1D)one-way waveguides based on topological edge states of two-dimensional(2D)gyromagnetic photonic crystals have been studied extensively.Here,we theoretically propose a three-dimensional(3D)all-dielectric gyromagnetic photonic crystal with type-Ⅱ Weyl points.Based on the inclined band properties of the type-Ⅱ Weyl surface states,we design a 2D one-way interface transmission channel on the Weyl crystal.Light waves in such 2D waveguides can be transmitted robustly over metal obstacles almost without any back-reflection,topologically protected by the type-Ⅱ Weyl points.By manipulating the magnetic field or structural parameters,we also achieve the topological phase transition between Weyl phase and 3D Chern insulator phase and obtain the corresponding phase diagram,which provides more possibilities for topological regulation of the surface states.This work suggests a new way to construct unidirectional 2D waveguides with larger area of energy transmission in 3D space,which is a promising platform for developing 3D topological photonic devices.
