Recently,intrinsic antiferromagnetic topological insulator MnBi_(2)Te_(4) has drawn intense research interest and leads to plenty of significant progress in physics and materials science by hosting quantum anomalous H...Recently,intrinsic antiferromagnetic topological insulator MnBi_(2)Te_(4) has drawn intense research interest and leads to plenty of significant progress in physics and materials science by hosting quantum anomalous Hall effect,axion insulator state,and other quantum phases.An essential ingredient to realize these quantum states is the magnetic gap in the topological surface states induced by the out-of-plane ferromagnetism on the surface of MnBi_(2)Te_(4).However,the experimental observations of the surface gap remain controversial.Here,we report the observation of the surface gap via the point contact tunneling spectroscopy.In agreement with theoretical calculations,the gap size is around 50 me V,which vanishes as the sample becomes paramagnetic with increasing temperature.The magnetoresistance hysteresis is detected through the point contact junction on the sample surface with an out-of-plane magnetic field,substantiating the surface ferromagnetism.Furthermore,the non-zero transport spin polarization coming from the ferromagnetism is determined by the point contact Andreev reflection spectroscopy.Combining these results,the magnetism-induced gap in topological surface states of MnBi_(2)Te_(4) is revealed.展开更多
基金Supported by the National Key Research and Development Program of China (Grant Nos. 2017YFA0303302,2018YFA0305604,2018YFA0307100)the National Natural Science Foundation of China (Grant Nos. 11888101,11774008,11704279,11874035,51788104)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB28000000)the Beijing Natural Science Foundation (Grant Nos. Z180010 and 1202005)the Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics,Tsinghua University (Grant No. KF202001)
文摘Recently,intrinsic antiferromagnetic topological insulator MnBi_(2)Te_(4) has drawn intense research interest and leads to plenty of significant progress in physics and materials science by hosting quantum anomalous Hall effect,axion insulator state,and other quantum phases.An essential ingredient to realize these quantum states is the magnetic gap in the topological surface states induced by the out-of-plane ferromagnetism on the surface of MnBi_(2)Te_(4).However,the experimental observations of the surface gap remain controversial.Here,we report the observation of the surface gap via the point contact tunneling spectroscopy.In agreement with theoretical calculations,the gap size is around 50 me V,which vanishes as the sample becomes paramagnetic with increasing temperature.The magnetoresistance hysteresis is detected through the point contact junction on the sample surface with an out-of-plane magnetic field,substantiating the surface ferromagnetism.Furthermore,the non-zero transport spin polarization coming from the ferromagnetism is determined by the point contact Andreev reflection spectroscopy.Combining these results,the magnetism-induced gap in topological surface states of MnBi_(2)Te_(4) is revealed.
