摘要
Traditionally topological phase transition describes an evolution from topological trivial to topological nontrivial state.Originated from the non-symmorphic crystalline symmetry,we propose in this work an unconventional topological phase transition scheme between two topological nontrivial insulating states mediated by a Dirac gapless state,differing from the traditional topological phase transition.The KHgX(X=As,Sb,Bi)family is the first experimentally realized topological non-symmorphic crystalline insulator(TNCI),where the topological surface states are characterized by the Mobius-twisted connectivity.Based on first-principles calculations,we present a topological insulator–metal transition from TNCI into a Dirac semimetal(DSM)via applying an external pressure on KHgX.We find an unusual mirror Chern number C_(m)=−3 for the DSM phase of KHgX in the non-symmorphic crystal structure,which is topologically distinct from the traditional DSM such as Na_(3)Bi and Cd_(3)As_(2).Furthermore,we predict a new TNCI phase in KHgX via symmetry breaking.The topological surface states in this new TNCI phase display zigzag connectivity,different from the unstressed one.Our results offer a comprehensive study for understanding how the topological surface states evolve from a quantum phase transition in non-symmorphic system.
基金
This work was supported by the Ministry of Science and Technology,Taiwan,Grant Nos.MOST 107-2627-E-006-001 and MOST 106-2112-M-007-012-MY3
T.-R.C.was supported from Young Scholar Fellowship Program by Ministry of Science and Technology(MOST)in Taiwan,under MOST Grant for the Columbus Program MOST108-2636-M-006-002。
