The nontrivial band topologies protected by certain symmetries have attracted significant interest in condensed matter physics.The discoveries of nontrivial topological phases in real materials provide a series of arc...The nontrivial band topologies protected by certain symmetries have attracted significant interest in condensed matter physics.The discoveries of nontrivial topological phases in real materials provide a series of archetype materials to further explore the topological physics.展开更多
Predicting new Dirac semimetals,as well as other topological materials,is challenging since the relationship between crystal structure,atoms and band topology is complex and elusive.Here,we demonstrate an approach to ...Predicting new Dirac semimetals,as well as other topological materials,is challenging since the relationship between crystal structure,atoms and band topology is complex and elusive.Here,we demonstrate an approach to design Dirac semimetals via exploring chemical degree of freedom.Based on understanding of the well-known Dirac semimetal,Na3Bi,three compounds in one family,namely Na_(2)MgSn,Na_(2)MgPb,and Na2CdSn,are located.Furthermore,hybrid-functional calculations with improved accuracy for estimation of band inversion show that Na_(2)MgPb and Na_(2)CdSn have the band topology of Dirac semimetals.The nontrivial surface states with Fermi arcs on the(100)and(010)surfaces are shown to connect the projection of bulk Dirac nodes.Most importantly,the candidate compounds are dynamically stable and have been experimentally synthesized.The ideas in this work could stimulate further predictions of topological materials based on understanding of existing ones.展开更多
The magnetic Weyl semimetal(WSM)is important for fundamental physics and potential applications due to its spontaneous magnetism,robust band topology,and enhanced Berry curvature.It possesses many unique quantum effec...The magnetic Weyl semimetal(WSM)is important for fundamental physics and potential applications due to its spontaneous magnetism,robust band topology,and enhanced Berry curvature.It possesses many unique quantum effects,including a large intrinsic anomalous Hall effect,Fermi arcs,and chiral anomaly.In this work,using ab initio calculations,we propose that Nidoped pyrochlore Tl2Nb2O7is a magnetic WSM caused by the exchange field splitting on bands around its quadratic band crossing point.The exchange field tuned by Ni 3d on-site Coulomb interaction parameter U drives the evolution of Weyl nodes and the resulting topological phase transition.As Weyl nodes can exist at generic points in the Brillouin zone and are hard to identify exactly,their creation and annihilation,i.e.,the change in their number,chirality,and distribution,have been consistently confirmed with a combined theoretical approach,which employs parity criterion,symmetry indicator analysis,and the Wilson loop of the Wannier center.We find that Weyl nodes remain in a large range of U and are close to the Fermi level,which makes the experimental observation very possible.We think that this method and our proposal of magnetic WSM will be useful in finding more WSMs and add to the understanding of the topological phase transition.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12374159 and 11974076)the Key Project of Natural Science Foundation of Fujian Province,China(Grant No.2021J02012)+1 种基金the GHfund A(Grant No.202302019222)the Research Foundation of the Academy of Carbon Neutrality of Fujian Normal University,China(Grant No.TZH2022-05)。
文摘The nontrivial band topologies protected by certain symmetries have attracted significant interest in condensed matter physics.The discoveries of nontrivial topological phases in real materials provide a series of archetype materials to further explore the topological physics.
基金This work is supported by the the National Key Research and Development Program of China(No.2016YFA0300600 and 2018YFA0305700)the National Natural Science Foundation of China(Grant Nos.11374063 and 11674369)the“Strategic Priority Research Program(B)”of the Chinese Academy of Sciences(Grant No.XDB07020100).
文摘Predicting new Dirac semimetals,as well as other topological materials,is challenging since the relationship between crystal structure,atoms and band topology is complex and elusive.Here,we demonstrate an approach to design Dirac semimetals via exploring chemical degree of freedom.Based on understanding of the well-known Dirac semimetal,Na3Bi,three compounds in one family,namely Na_(2)MgSn,Na_(2)MgPb,and Na2CdSn,are located.Furthermore,hybrid-functional calculations with improved accuracy for estimation of band inversion show that Na_(2)MgPb and Na_(2)CdSn have the band topology of Dirac semimetals.The nontrivial surface states with Fermi arcs on the(100)and(010)surfaces are shown to connect the projection of bulk Dirac nodes.Most importantly,the candidate compounds are dynamically stable and have been experimentally synthesized.The ideas in this work could stimulate further predictions of topological materials based on understanding of existing ones.
基金supported by the National Natural Science Foundation of China(Grant Nos.11974076,11925408,11921004,and 12188101)Key Project of Natural Science Foundation of Fujian Province(Grant No.2021J02012)+4 种基金Ministry of Science and Technology of China(Grant No.2018YFA0305700)Chinese Academy of Sciences(Grant No.XDB33000000)K.C.Wong Education Foundation(Grant No.GJTD-2018-01)Informatization Plan of Chinese Academy of Sciences(Grant No.CAS-WX2021SF-0102)supported by the Swiss National Science Foundation(Grant No.200021-196966)。
文摘The magnetic Weyl semimetal(WSM)is important for fundamental physics and potential applications due to its spontaneous magnetism,robust band topology,and enhanced Berry curvature.It possesses many unique quantum effects,including a large intrinsic anomalous Hall effect,Fermi arcs,and chiral anomaly.In this work,using ab initio calculations,we propose that Nidoped pyrochlore Tl2Nb2O7is a magnetic WSM caused by the exchange field splitting on bands around its quadratic band crossing point.The exchange field tuned by Ni 3d on-site Coulomb interaction parameter U drives the evolution of Weyl nodes and the resulting topological phase transition.As Weyl nodes can exist at generic points in the Brillouin zone and are hard to identify exactly,their creation and annihilation,i.e.,the change in their number,chirality,and distribution,have been consistently confirmed with a combined theoretical approach,which employs parity criterion,symmetry indicator analysis,and the Wilson loop of the Wannier center.We find that Weyl nodes remain in a large range of U and are close to the Fermi level,which makes the experimental observation very possible.We think that this method and our proposal of magnetic WSM will be useful in finding more WSMs and add to the understanding of the topological phase transition.
基金supported by the National Natural Science Foundation of China(11974076,11925408,11921004,and 12188101)the Key Project of Natural Science Foundation of Fujian Province(2021J02012)+4 种基金the Ministry of Science and Technology of China(2018YFA0305700)the Chinese Academy of Sciences(XDB33000000 and CAS-WX2021SF-0102)the K.C.Wong Education Foundation(GJTD-2018–01)the Key Research Project of Zhejiang Lab(2021PB0AC01)supported by the Swiss National Science Foundation(200021–196966)。