The Adsorption Modification Of Bismuth Clusters And EDTA-Dy Molecules On Graphene And Its Spin-orbit Coupling

Graphene,a material made of a two-dimensional honeycomb carbon lattice,is acting as a bridge between quantum field theory and condensed matter physics owing to its gapless,massless and chiral Dirac spectrum.Its excellent physical and chemical properties make graphene become a hot spot in the scientific research of nanomaterials.Decorating graphene with clusters and molecules,not only can adjust the properties of graphene,but also can use the two-dimensional electron gas platform,i.e.graphene,to explore the electrical properties of clusters.In the work,we decorate the graphene devices with Bismuth clusters and EDTA-Dy molecules,so as to explore the influence of clusters and molecules on the quantum transport properties of graphene.The main results are summarized as followed:(1)We measure the transport behavior of graphene decorated with Bismuth clusters at low temperature,and observe the change in feature of weak localization.We deposit Bi clusters on graphene devices with cluster beam deposition system,and measure the transport behavior of graphene devices before and after deposition at low temperature with high vacuum magnetoresistance measurement system.By analyzing the weak localization data of graphene at various gate voltages and temperatures systematically,we observe the effect of Bi clusters on the spin-orbit interaction(SOI)of graphene.The SOI strength is found to be enhanced to 2.64 meV by the first deposition of Bi cluster.According to the results after the second cluster deposition,we discuss the effect of cluster coverage on weak localization and SOI of the graphene device.(2)The dressing of EDTA-Dy molecules can improve the transport performance of graphene devices,and the increased ripple mimic the Kane-Mele type SOI with flexural phonon mode.We dress the graphene devices with aqueous EDTA-Dy molecules,and low-temperature measurements show that the dressing of EDTA-Dy molecules can decrease the concentration of hole carrier,with improved half-integer quantum Hall transport.With the analysis of weak localization data of graphene before and after the molecules dressing,we find that the SOI strength of graphene can be enhanced to 3.3 meV.Such subtle control of the electronic properties is attributed to the ripple-induced flexural phonon as demonstrated by the magnetoresistance measurement under vector magnet.This work is also important as the first macroscopic transport effect of the gauge field of graphene ripples.