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Universal Conductance Fluctuation Due to Development of Weak Localization in Monolayer Graphene
摘要： The relationship between two quantum interference effects, the universal conductance fluctuation (UCF) and the weak localization (WL), is investigated in monolayer graphene. We find that the local maxima in the UCF as a function of the gate voltage (Fermi energy) show stronger WL resistivity correction. By comparing experimental results with the predictions of the WL theory, we find that the ratio of the inelastic dephasing length to the elastic intervalley scattering length varies in accordance with the UCF. Furthermore, the temperature dependence of the UCF amplitude is also well described by the theory of WL resistivity correction. Therefore, we propose that the UCF can be attributed to the WL in graphene. In addition, we investigate the UCF in the presence of the magnetic field perpendicular to the graphene sheet. Our fast Fourier transform analysis of the magnetic field dependence of the UCF reveals a length scale that is related to the phase shift caused by the Aharonov–Bohm effect. We discuss the relationship between this effective length and the elastic scattering lengths.
关键词： graphene,weak localization,universal conductance fluctuation,Aharonov–Bohm effect
更新于2025-09-19 17:15:36
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Transition between Electron Localization and Antilocalization and Manifestation of the Berry Phase in Graphene on a SiC Surface
摘要： It is shown that the transport properties of graphitized silicon carbide are controlled by a surface graphene layer heavily doped with electrons. In weak magnetic fields and at low temperatures, a negative magnetoresistance is observed due to weak localization. A crossover in the magnetoresistance from weak localization to weak antilocalization (the latter is the manifestation of the isospin in graphene) is observed for the first time in samples of this kind at elevated temperatures. A pronounced pattern of Shubnikov–de Haas oscillations is observed in strong magnetic fields (up to 30 T). This pattern demonstrated fourfold carrier spectrum degeneracy due to the double spin and double valley degeneracies. Also, the manifestation of the Berry phase is observed. The effective electron mass is estimated to be m* = 0.08m0, which is characteristic of graphene with a high carrier concentration.
关键词： weak localization,Berry phase,graphene,Shubnikov–de Haas oscillations,silicon carbide,magnetoresistance,weak antilocalization
更新于2025-09-11 14:15:04
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heterostructures
摘要： The weak intrinsic spin-orbit coupling in graphene can be greatly enhanced by proximity coupling. Here, we report on the proximity-induced spin-orbit coupling in graphene transferred by hexagonal boron nitride (hBN) onto the topological insulator Bi1.5Sb0.5Te1.7Se1.3 (BSTS) which was grown on a hBN substrate by vapor solid synthesis. Phase coherent transport measurements, revealing weak localization, allow us to extract the carrier density-dependent phase coherence length lφ. While lφ increases with increasing carrier density in the hBN/graphene/hBN reference sample, it decreases in graphene/BSTS due to the proximity coupling of BSTS to graphene. The latter behavior results from D’yakonov-Perel’-type spin scattering in graphene with a large proximity-induced spin-orbit coupling strength of at least 2.5 meV.
关键词： weak localization,topological insulator,graphene,proximity effect,spin-orbit coupling
更新于2025-09-09 09:28:46
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Stable Hall voltages in presence of dynamic quasi-continuum bands in poly(3,4-ethylene-dioxythiophene)
摘要： Topological and thermal disorder complicate the mobility characterization in poly(3,4-ethylenedioxythiophene) systems and presently leaves the exact transport mechanisms not fully understood. Here we show that ac-Hall measured by lock-in amplifier is able to resolve the Hall voltage in semimetallic polymers between room temperature and 32 K. These results are evaluated using an organic random phase model. This accounts for the role of tail states and, particularly, for thermal disorder of molecular semiconductors. We report band mobilities up to 3.7 cm2 V?1 s?1 in semimetallic polymers occurring in delocalized bands that originate from significant electron coherence across the polymer chains.
关键词： Weak localization,Conducting polymers,PEDOT,Hall-effect,Organic phase model,Electron coherence
更新于2025-09-04 15:30:14