Weak localization in monolayer and bilayer graphene

Horsell, D. W.; Tikhonenko, F. V.; Gorbachev, Roman; Savchenko, A. K.

doi:10.1098/rsta.2007.2159

Cited by 51 publications

(26 citation statements)

References 10 publications

(28 reference statements)

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“…Because of the existence of a Berry phase in monolayer graphene, 3 the two trajectories are expected to gain a phase difference of π , leading to destructive interference and hence weak antilocalization. 20 However, in the presence of significant elastic intervalley scattering (τ i ), weak localization can be restored. The reason for this is that chirality is reversed between the two valleys; 21 hence trajectories involving intervalley scattering allow for zero phase difference between two self-intersecting paths which leads to constructive interference and hence weak localization.…”

Section: Methodology and Theoretical Backgroundmentioning

confidence: 99%

Weak localization scattering lengths in epitaxial, and CVD graphene

et al. 2012

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Weak localization in graphene is studied as a function of carrier density in the range from 1 × 10 11 cm −2 to 1.43 × 10 13 cm −2 using devices produced by epitaxial growth onto SiC and CVD growth on thin metal film. The magnetic field dependent weak localization is found to be well fitted by theory, which is then used to analyze the dependence of the scattering lengths L ϕ , L i , and L * on carrier density. We find no significant carrier dependence for L ϕ , a weak decrease for L i with increasing carrier density just beyond a large standard error, and a n −1/4 dependence for L * . We demonstrate that currents as low as 0.01 nA are required in smaller devices to avoid hot-electron artifacts in measurements of the quantum corrections to conductivity.

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Section: Methodology and Theoretical Backgroundmentioning

confidence: 99%

Weak localization scattering lengths in epitaxial, and CVD graphene

et al. 2012

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“…WAL is theoretically expected in graphene in the absence of inter-valley and chirality breaking scattering. [17] Most studies have not presented clear evidence of WAL via negative magnetoconductance, [18][19][20][21][22] most likely due to presence of point defects in graphene samples that locally break the sublattice degeneracy and smooth out !-phase contribution. Experimental signatures of WAL observed in high-quality epitaxial graphene samples are attributed to suppressed point defects.…”

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confidence: 99%

Room‐Temperature Quantum Transport Signatures in Graphene/LaAlO₃/SrTiO₃ Heterostructures

et al. 2017

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2Weak localization (WL) and weak antilocalization (WAL) are quantum interference effects [1][2][3][4] resulting from electron phase coherence and spin-orbit interactions in 2-dimensional (2D) electron systems. WL results from constructive interference between pairs of time-reversed closed-loop electron trajectories and provides a positive correction to the Drude resistivity. [2, 4] Spin-orbit coupling (SOC) leads to suppressed backscattering due to destructive interference, leading to WAL and a negative correction to the Drude resistivity.[3]The intrinsic SOC of graphene is weak; [5] however, charge carriers in graphene possess a pseudospin degree of freedom, which arises from the degeneracy introduced by the two inequivalent atomic sites per unit cell in the graphene honeycomb lattice being comprised of A and B sublattices[ Figure 1(a) and (b)]. [6, 7] Recent discovery of unique quantum transport phenomena in graphene, such as unconventional half-integer quantum Hall effect [7, 8] and Klein tunneling [9][10][11] is a direct consequence of non-trivial Berry phase of ! induced by pseudospin rotation. Pseudospin in graphene can be utilized to store and manipulate information, which is analogous to the spin degree of freedom in spintronics. [12][13][14][15][16] Because of pseudospin rotation, each scattering process has a phase difference of ! between two time reversal pair in a closed quantum diffusive path. This results in destructive interference that suppresses backscattering, leading to WAL in graphene, which is analogous to the role of SOC (Figure 1(c) and (d)) in ordinary semiconductors. WAL is theoretically expected in graphene in the absence of inter-valley and chirality breaking scattering. [17] Most studies have not presented clear evidence of WAL via negative magnetoconductance, [18][19][20][21][22] most likely due to presence of point defects in graphene samples that locally break the sublattice degeneracy and smooth out !-phase contribution. Experimental signatures of WAL observed in high-quality epitaxial graphene samples are attributed to suppressed point defects.[23]Interestingly, a WL to WAL transition is achieved in high quality exfoliated samples [24] by decreasing the ratio of the dephasing length to the symmetry-breaking length via decoherence and carrier-density control. 3Preservation of pseudospin quantum interference up to room temperature (RT) is of fundamental importance for a variety of proposed applications, [12-16, 25, 26] but thermal perturbations typically suppress the phase coherence and hinder practical use of the devices. RT operation can be achieved if the high graphene mobility is consistently maintained over a broad temperature range and phonon-scattering contribution is significantly reduced. The mobility of graphene field-effect devices fabricated on SiO 2 /Si substrates is typically reduced at RT due to scattering with surface polar modes. [20,27,28] A significant improvement in quality was achieved by fabricating graphene devices on hexagonal-boron nitride (hBN) ...

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“…Note that (i) the number of fitting parameters is effectively four, the minimum number used in most WAL studies, because the rates for the n region are nearly the same as those for the p region in the case of a small V tg ; and (ii) because the digamma function has a sufficiently non-trivial dependence on its argument, the overall factor a is not important in determining the rates in the fitting, because the dependence of equation (5) on B is not governed by a, but by the rates. In the fitting, we used two physically reasonable constraints: (i) that the intervalley scattering rate is smaller than the intravalley scattering rate 56 , t À 1 i nðpÞ t À 1 Ã nðpÞ and (ii) that all scattering rates are smaller than the momentum relaxation rate 33,38 , t …”

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confidence: 99%

Complete gate control of supercurrent in graphene p–n junctions

et al. 2013

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In a conventional Josephson junction of graphene, the supercurrent is not turned off even at the charge neutrality point, impeding further development of superconducting quantum information devices based on graphene. Here we fabricate bipolar Josephson junctions of graphene, in which a p-n potential barrier is formed in graphene with two closely spaced superconducting contacts, and realize supercurrent ON/OFF states using electrostatic gating only. The bipolar Josephson junctions of graphene also show fully gate-driven macroscopic quantum tunnelling behaviour of Josephson phase particles in a potential well, where the confinement energy is gate tuneable. We suggest that the supercurrent OFF state is mainly caused by a supercurrent dephasing mechanism due to a random pseudomagnetic field generated by ripples in graphene, in sharp contrast to other nanohybrid Josephson junctions. Our study may pave the way for the development of new gate-tuneable superconducting quantum information devices.

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Weak localization in monolayer and bilayer graphene

Cited by 51 publications

References 10 publications

Weak localization scattering lengths in epitaxial, and CVD graphene

Weak localization scattering lengths in epitaxial, and CVD graphene

Room‐Temperature Quantum Transport Signatures in Graphene/LaAlO₃/SrTiO₃ Heterostructures

Complete gate control of supercurrent in graphene p–n junctions

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Weak localization in monolayer and bilayer graphene

Cited by 51 publications

References 10 publications

Weak localization scattering lengths in epitaxial, and CVD graphene

Weak localization scattering lengths in epitaxial, and CVD graphene

Room‐Temperature Quantum Transport Signatures in Graphene/LaAlO3/SrTiO3 Heterostructures

Complete gate control of supercurrent in graphene p–n junctions

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Room‐Temperature Quantum Transport Signatures in Graphene/LaAlO₃/SrTiO₃ Heterostructures