Induced magneto-conductivity in a two-nodeWeyl semimetal under Gaussian random disorder

Measuring the magneto-conductivity induced from impurities may help determine the impurity distribution and reveal the structure of a Weyl semimetal sample.To verify this,we utilize the Gaussian random disorder to simulate charged impurities in a two-node Weyl semimetal model and investigate the impact of charged impurities on magneto-conductivity in Weyl semimetals.We first compute the longitudinal magnetic conductivity and find that it is positive and increases proportionally with the parameter governing the Gaussian distribution of charged impurities,suggesting the presence of negative longitudinal magneto-resistivity.Then we consider both the intra-valley and inter-valley scattering processes to calculate the induced transverse magneto-conductivity in the model.Our findings indicate that both inter-valley and intravalley scattering processes play important roles in the transverse magneto-conductivity.The locations of Weyl nodes can also be determined by magneto-conductivity measurements.This is possible if the magnetic field strength and the density of charged impurities are known.Alternatively,the measurement of magnetic conductivity may reveal the distribution of charged impurities in a given sample once the locations of the Weyl nodes have been determined.These findings can aid in detecting the structure of a Weyl semimetal sample,enhancing comprehension of magnetotransport in Weyl semimetals and promoting the development of valley electronics.

Local measurements of tunneling magneto-conductance oscillations in monolayer, Bernal-stacked bilayer, and ABC-stacked trilayer graphene

Shubnikov-de Haas oscillations are the most well-known magneto-oscillations in transport measurements. They are caused by Landau quantization of two-dimensional(2D) electron systems in the presence of a magnetic field. Here we demonstrate that a scanning tunneling microscope(STM) can locally measure similar magneto-oscillations in 2D systems. In Landau level spectroscopy measurements with fine magnetic-field increments, we observed fixed-energy magnetic-field-dependent oscillations of the local density of states. From the measured tunneling magneto-conductance oscillations acquired by STM, energymomentum dispersions and Berry phases of a monolayer, Bernal-stacked bilayer, and ABC-stacked trilayer graphene were obtained. The reported method is applicable to a wide range of materials because it can obtain the magneto-oscillations of 2D systems larger than the magnetic length;importantly, it also requires no gate electrode.