Weak localization and universal conductance fluctuations in multi-layer graphene |
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Affiliation: | 1. Department of Physics, National Taiwan University, Taipei 106, Taiwan, ROC;2. Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan;3. Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan, ROC;4. Department of Physics, National Chung Cheng University, Chiayi 621, Taiwan, ROC;5. Department of Electrophysics, National Chiayi University, Chiayi 600, Taiwan, ROC;6. School of Electronic and Electrical Engineering, Sungkyunkwan University, Suwon 440-746, Republic of Korea |
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Abstract: | We have performed magneto transport measurements on a multi-layer graphene device fabricated by conventional mechanical exfoliation. Suppression of weak localization (WL) as evidenced by the negative magnetoresistance (NMR) centered at zero field, and reproducible universal conductance fluctuations (UCFs) are observed. Interestingly, it is found that the phase coherence lengths calculated by fitting the observed NMR to conventional WL theory are longer than those determined from fitting the amplitudes of the UCFs to theory in the low temperature regime (T ≤ 8 K). In the high temperature regime (T > 8 K), the phase coherence lengths calculated by fitting the observed NMR to conventional WL theory are shorter than those determined from fitting the amplitudes of the UCFs to theory. Our new results therefore indicate a difference in the electron phase-breaking process between the two models of WL and UCFs in graphene. We speculate that the presence of the capping and bottom graphene layers, which leads the enhancement of disorder in-between, improves the localization condition for WL effect during carrier transportation in the low temperature regime. With increasing temperature, the localization condition for WL in multi-layer graphene becomes much weaker due to strong thermal damping. Therefore, the phase coherence lengths calculated by fitting the observed NMR to conventional WL theory are shorter than those determined from fitting the amplitudes of the UCFs to theory at high temperatures. |
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Keywords: | Graphene Conductance fluctuations Phase coherence |
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