Abstract
The pseudo-magnetic field generated by mechanical strain in graphene can have dramatic consequences on the behavior of electrons and holes. Here we show that pseudo-magnetic field fluctuations present in crumpled graphene can induce significant intravalley scattering of charge carriers. We detect this by measuring the confocal Raman spectra of crumpled areas, where we observe an increase of the D′/D peak intensity ratio by up to a factor of 300. We reproduce our observations by numerical calculation of the double resonant Raman spectra and interpret the results as experimental evidence of the phase shift suffered by Dirac charge carriers in the presence of a pseudo-magnetic field. This lifts the restriction on complete intravalley backscattering of Dirac fermions.
Highlights
With the discovery of the half integer quantum Hall effect in graphene[1,2] and of topological materials,[3,4] Berry phase effects have taken center stage in condensed matter research
In this case, scattering between the two valleys is suppressed and the pseudospin is conserved,[5] leading to some important effects that are the hallmark of graphene, such as weak antilocalization,[7] the half integer quantum Hall effect[1,2] and Klein tunneling.[5,8]
The intravalley to intervalley scattering peak intensity ratio is found to be as high as ID′/ID = 30, in contrast to the usual value of ≈0.1.12 Since the strain induced pseudo-magnetic field (Bps) couples to the pseudospin,[13,14] the enhancement of the D′ peak at 1620 cm−1 is due to the extra phase acquired by charge carriers undergoing
Summary
With the discovery of the half integer quantum Hall effect in graphene[1,2] and of topological materials,[3,4] Berry phase effects have taken center stage in condensed matter research. The intravalley to intervalley scattering peak intensity ratio is found to be as high as ID′/ID = 30, in contrast to the usual value of ≈0.1.12 Since the strain induced pseudo-magnetic field (Bps) couples to the pseudospin,[13,14] the enhancement of the D′ peak at 1620 cm−1 is due to the extra phase acquired by charge carriers undergoing
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