Twisted bilayer graphene(TBG) has been extensively studied because of its novel physical properties and potential application in electronic devices.Here we report the synthesis and characterization of 300 TBG naturall...Twisted bilayer graphene(TBG) has been extensively studied because of its novel physical properties and potential application in electronic devices.Here we report the synthesis and characterization of 300 TBG naturally grown on Cu_(0.75)Ni_(0.25)(111) film and investigate the electronic structure by angle-resolved photoemission spectroscopy.Compared with other substrates,our TBG with a wafer scale is acquired with a shorter growth time.The Fermi velocity and energy gap of Dirac cones of TBG are comparable with those of a monolayer on Cu_(0.85)Ni_(0.15)(111).The signature of moré lattices has not been observed in either the low-energy electron diffraction patterns or the Fermi surface map within experimental resolution,possibly due to different Cu and Ni contents in the substrates enhancing the different couplings between the substrate and the first/second layers and hindering the formation of a quasiperiodic structure.展开更多
Magnetic topological states of matter provide a fertile playground for emerging topological physics and phenomena.The current main focus is on materials whose magnetism stems from 3d magnetic transition elements,e.g.,...Magnetic topological states of matter provide a fertile playground for emerging topological physics and phenomena.The current main focus is on materials whose magnetism stems from 3d magnetic transition elements,e.g.,MnBi_(2)Te_(4),Fe_(3)Sn_(2),and Co_(3)Sn_(2)S_(2).In contrast,topological materials with the magnetism from rare earth elements remain largely unexplored.Here we report rare earth antiferromagnet GdAuAl_(4)Ge_(2)as a candidate magnetic topological metal.Angle resolved photoemission spectroscopy(ARPES)and first-principles calculations have revealed multiple bulk bands crossing the Fermi level and pairs of low energy surface states.According to the parity and Wannier charge center analyses,these bulk bands possess nontrivial Z2 topology,establishing a strong topological insulator state in the nonmagnetic phase.Furthermore,the surface band pairs exhibit strong termination dependence which provides insight into their origin.Our results suggest GdAuAl_(4)Ge_(2)as a rare earth platform to explore the interplay between band topology,magnetism and f electron correlation,calling for further study targeting on its magnetic structure,magnetic topology state,transport behavior,and microscopic properties.展开更多
The simple kagome-lattice band structure possesses Dirac cones,flat band,and saddle point with van Hove singularities in the electronic density of states,facilitating the emergence of various electronic orders.Here we...The simple kagome-lattice band structure possesses Dirac cones,flat band,and saddle point with van Hove singularities in the electronic density of states,facilitating the emergence of various electronic orders.Here we report a titanium-based kagome metal CsTi_(3)Bi_(5)where titanium atoms form a kagome network,resembling its isostructural compound CsV_3Sb_5.Thermodynamic properties including the magnetization,resistance,and heat capacity reveal the conventional Fermi liquid behavior in the kagome metal CsTi_(3)Bi_(5)and no signature of superconducting or charge density wave(CDW)transition anomaly down to 85 m K.Systematic angle-resolved photoemission spectroscopy measurements reveal multiple bands crossing the Fermi level,consistent with the first-principles calculations.The flat band formed by the destructive interference of hopping in the kagome lattice is observed directly.Compared to Cs V_(3)Sb_(5),the van Hove singularities are pushed far away above the Fermi level in CsTi_(3)Bi_(5),in line with the absence of CDW.Furthermore,the first-principles calculations identify the nontrivial Z_(2)topological properties for those bands crossing the Fermi level,accompanied by several local band inversions.Our results suppose CsTi_(3)Bi_(5)as a complementary platform to explore the superconductivity and nontrivial band topology.展开更多
In our most recently published article,[1]an important reference[2]predicting CsTi_(3)Bi_(5) is missing and should be added,along with Ref.[3](originally Ref.[28]),to the introduction section.
基金Project supported by the National Key R&D Program of China (Grant Nos. 2022YFB3608000 and 2022YFA1204900)the National Natural Science Foundation of China (Grant Nos. 12222413 and 12074205)+2 种基金the Natural Science Foundation of Shanghai (Grant Nos. 23ZR1482200 and 22ZR1473300)the Natural Science Foundation of Zhejiang Province (Grant No. LQ21A040004)the funding of Ningbo University (Grant No. LJ2024003)。
文摘Twisted bilayer graphene(TBG) has been extensively studied because of its novel physical properties and potential application in electronic devices.Here we report the synthesis and characterization of 300 TBG naturally grown on Cu_(0.75)Ni_(0.25)(111) film and investigate the electronic structure by angle-resolved photoemission spectroscopy.Compared with other substrates,our TBG with a wafer scale is acquired with a shorter growth time.The Fermi velocity and energy gap of Dirac cones of TBG are comparable with those of a monolayer on Cu_(0.85)Ni_(0.15)(111).The signature of moré lattices has not been observed in either the low-energy electron diffraction patterns or the Fermi surface map within experimental resolution,possibly due to different Cu and Ni contents in the substrates enhancing the different couplings between the substrate and the first/second layers and hindering the formation of a quasiperiodic structure.
基金Project supported by the National Key Research and Development Program of China (Grant No. 2022YFA1403700)the National Natural Science Foundation of China (Grant No. 12074163)+2 种基金the Basic and Applied Basic Research Foundation of Guangdong Province, China (Grants Nos. 2022B1515020046, 2022B1515130005, and 2021B1515130007)the Innovative and Entrepreneurial Research Team Program of Guangdong Province, China (Grant Nos. 2019ZT08C044)Shenzhen Science and Technology Program (Grant No. KQTD20190929173815000)
文摘Magnetic topological states of matter provide a fertile playground for emerging topological physics and phenomena.The current main focus is on materials whose magnetism stems from 3d magnetic transition elements,e.g.,MnBi_(2)Te_(4),Fe_(3)Sn_(2),and Co_(3)Sn_(2)S_(2).In contrast,topological materials with the magnetism from rare earth elements remain largely unexplored.Here we report rare earth antiferromagnet GdAuAl_(4)Ge_(2)as a candidate magnetic topological metal.Angle resolved photoemission spectroscopy(ARPES)and first-principles calculations have revealed multiple bulk bands crossing the Fermi level and pairs of low energy surface states.According to the parity and Wannier charge center analyses,these bulk bands possess nontrivial Z2 topology,establishing a strong topological insulator state in the nonmagnetic phase.Furthermore,the surface band pairs exhibit strong termination dependence which provides insight into their origin.Our results suggest GdAuAl_(4)Ge_(2)as a rare earth platform to explore the interplay between band topology,magnetism and f electron correlation,calling for further study targeting on its magnetic structure,magnetic topology state,transport behavior,and microscopic properties.
基金the National Key R&D Program of China(Grant No.2022YFA1403700)the National Natural Science Foundation of China(Grant Nos.12074163 and 12004030)+5 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2022B1515020046,2022B1515130005,2021B1515130007,and 2020B1515120100)the Guangdong Innovative and Entrepreneurial Research Team Program(Grant Nos.2017ZT07C062 and 2019ZT08C044)the Shenzhen Science and Technology Program(Grant No.KQTD20190929173815000)Shenzhen Key Laboratory of Advanced Quantum Functional Materials and Devices(Grant No.ZDSYS20190902092905285)the Shenzhen Fundamental Research Program(Grant No.JCYJ20220818100405013)China Postdoctoral Science Foundation(Grant No.2020M682780 and 2022M711495)。
文摘The simple kagome-lattice band structure possesses Dirac cones,flat band,and saddle point with van Hove singularities in the electronic density of states,facilitating the emergence of various electronic orders.Here we report a titanium-based kagome metal CsTi_(3)Bi_(5)where titanium atoms form a kagome network,resembling its isostructural compound CsV_3Sb_5.Thermodynamic properties including the magnetization,resistance,and heat capacity reveal the conventional Fermi liquid behavior in the kagome metal CsTi_(3)Bi_(5)and no signature of superconducting or charge density wave(CDW)transition anomaly down to 85 m K.Systematic angle-resolved photoemission spectroscopy measurements reveal multiple bands crossing the Fermi level,consistent with the first-principles calculations.The flat band formed by the destructive interference of hopping in the kagome lattice is observed directly.Compared to Cs V_(3)Sb_(5),the van Hove singularities are pushed far away above the Fermi level in CsTi_(3)Bi_(5),in line with the absence of CDW.Furthermore,the first-principles calculations identify the nontrivial Z_(2)topological properties for those bands crossing the Fermi level,accompanied by several local band inversions.Our results suppose CsTi_(3)Bi_(5)as a complementary platform to explore the superconductivity and nontrivial band topology.
文摘In our most recently published article,[1]an important reference[2]predicting CsTi_(3)Bi_(5) is missing and should be added,along with Ref.[3](originally Ref.[28]),to the introduction section.
