Effect of Boundary Scattering on Magneto-Transport Performance in BN-Encapsulated Graphene
Lijun Zhu1,2,3, Lin Li1,2,3*, Xiaodong Fan1,2,3, Zhongniu Xie1,2,3, and Changgan Zeng1,2,3*
1CAS Key Laboratory of Strongly Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei 230026, China 2International Center for Quantum Design of Functional Materials (ICQD), Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China 3Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China
Abstract：For conductors in the ballistic regime, electron-boundary scattering at the sample edge plays a dominant role in determining the transport performance, giving rise to many intriguing phenomena like low-field negative magnetoresistance effect. We systematically investigate the magneto-transport behaviors of BN-encapsulated graphene devices with narrow channel width $W$, wherein the bulk mean free path $L_{\rm mfp}$ can be very large and highly tunable. By comparing the magnetoresistance features and the amplitude of $L_{\rm mfp}$ in a large parameter space of temperature and carrier density, we reveal that the boundary-scattering-dominated negative magnetoresistance effect can still survive even when the ballistic ratio ($L_{\rm mfp}/W$) is as low as 0.15. This striking value is much smaller than the expected value for achieving (quasi-) ballistic transport regime ($L_{\rm mfp}/W \ge 1$), and can be attributed to the ultra-low specularity of the sample edge of our graphene devices. These findings enrich our understanding of the effects of boundary scattering on channel transport, which is of vital importance for future designs of two-dimensional electronic devices with limited lateral sizes.
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2022, Vol. 39 
