Abstract
The surface states of three dimensional topological nodal line semimetal (TNLSM) form a flat band within the projection of the closed nodal line onto the surface. Such a flat band implies a singular surface density of states which, if close to the Fermi energy, is apt to induce a magnetic phase transition. Similar physics is expected in a two-dimensional (2D) TNLSM. In the framework of density functional theory, we study the edge states of Cu2Si monolayer which is currently an experimentally feasible sample of 2D TNLSM. We find that the flat bands attached to two kinds of zigzag edges of Cu2Si are very close to the Fermi energy. Moreover, we explore the possible magnetism of Cu2Si nanoribbons terminated by these zigzag edges. We find that a narrow ribbon has ferromagnetic ground states with sizable magnetic moments, owing to the interaction between the edge states localized at the opposite edges. In addition, carrier doping in a nanoribbon can induce the transition between the ferromagnetic and nonmagnetic states. More interestingly, the magnetic moment distribution in real space from one to another edges can be readily modulated by the carrier doping. Our study indicates that Cu2Si nanoribbons with controllable magnetism provide a new platform to realize the device functions of spintronics.
Published Version
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