Observation of logarithmic Kohn anomaly in monolayer graphene

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Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2020-10-23
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Language
en
Pages
6
Series
Physical Review B, Volume 102, issue 16
Abstract
Electron-phonon coupling in monolayer graphene breaks the adiabatic Born-Oppenheimer approximation and could lead to exotic logarithmic Kohn anomaly, manifested as logarithmic singularity in optical-phonon energy. However, unraveling unambiguously the fascinating logarithmic Kohn anomaly in monolayer graphene remains challenging due to the large carrier inhomogeneity originating from the unique massless Dirac-like band dispersion and the underneath substrate doping effect. Here we demonstrate a clear signature of intriguing logarithmic Kohn anomaly in monolayer graphene with ultralow carrier inhomogeneity via h-BN encapsulation. Significantly, the magnitude of anomalous phonon softening at 25 K shows an enhancement factor of 2 as compared to that previously observed in bilayer graphene at 12 K, even though bilayer graphene with nearly parabolic band dispersion is more immune to charged impurities. The uncovered unusual logarithmic Kohn anomaly in monolayer graphene can provide a firm basis for the understanding of various peculiar physics and may shed light on the nature of superconductivity in magic-angle graphene superlattices.
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| openaire: EC/H2020/820423/EU//S2QUIP | openaire: EC/H2020/834742/EU//ATOP
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Citation
Zhao , Y , Du , L , Yang , W , Shen , C , Tang , J , Li , X , Chu , Y , Tian , J , Watanabe , K , Taniguchi , T , Yang , R , Shi , D , Sun , Z & Zhang , G 2020 , ' Observation of logarithmic Kohn anomaly in monolayer graphene ' , Physical Review B , vol. 102 , no. 16 , 165415 . https://doi.org/10.1103/PhysRevB.102.165415