通过调控范霍夫奇点在外延单层VSe_(2)中诱导出巡游铁磁性

Inducing itinerant ferromagnetism by manipulating van Hove singularity in epitaxial monolayer 1T-VSe_(2)

处在费米能级处的范霍夫奇点(van Hove singularity)由于具有发散的态密度特征可以诱导出巡游铁磁性.本文在SrTiO_(3)(111)衬底上外延生长单层VSe_(2)薄膜,并通过调控范霍夫奇点诱导出巡游铁磁性.作者通过角分辨光电子能谱技术直接观测到了单层VSe_(2)中的范霍夫奇点能带结构.理论计算表明,当该范霍夫奇异点靠近费米能级时,可通过斯通纳(Stoner)不稳定性产生巡游铁磁性.实验上,作者利用SrTiO_(3)(111)在低温下极大增强的介电常数εr,通过界面电荷转移效应调控范霍夫奇点向费米能级处移动,并通过电输运测量观测到了3.3 K的巡游铁磁性转变.此外,通过改变薄膜层厚和更换衬底的方式,作者可以进一步调控界面电荷转移效果和范霍夫奇点的能量位置,并对巡游铁磁性进行调控.这项研究证明了范霍夫奇点可以成为巡游铁磁性的调控自由度,并拓展了二维磁体在未来电子信息技术的应用潜力.

The itinerant ferromagnetism can be induced by a van Hove singularity(VHS)with a divergent density of states at Fermi level.Utilizing the giant magnified dielectric constant of SrTiO_(3)(111)substrate with cooling,here we successfully manipulated the VHS in the epitaxial monolayer(ML)1T-VSe_(2) film approaching to Fermi level via the large interfacial charge transfer,and thus induced a two-dimensional(2D)itinerant ferromagnetic state below 3.3 K.Combining the direct characterization of the VHS structure via angle-resolved photoemission spectroscopy(ARPES),together with the theoretical analysis,we ascribe the manipulation of VHS to the physical origin of the itinerant ferromagnetic state in ML 1T-VSe_(2).Therefore,we further demonstrated that the ferromagnetic state in the 2D system can be controlled through manipulating the VHS by engineering the film thickness or replacing the substrate.Our findings clearly evidence that the VHS can serve as an effective manipulating degree of freedom for the itinerant ferromagnetic state,expanding the application potentials of 2D magnets for the next-generation information technology.