Abstract
We report on asymmetric electron-hole decoherence in epitaxial graphene gated by an ionic liquid. The observed negative magnetoresistance near zero magnetic field for different gate voltages, analyzed in the framework of weak localization, gives rise to distinct electron-hole decoherence. The hole decoherence rate increases prominently with decreasing negative gate voltage while the electron decoherence rate does not exhibit any substantial gate dependence. Quantitatively, the hole decoherence rate is as large as the electron decoherence rate by a factor of two. We discuss possible microscopic origins including spin-exchange scattering consistent with our experimental observations.
Highlights
In disordered conductors, the wave nature of electrons introduces a small quantum interference correction to resistance known as weak localization[8]
The achieved carrier density for electrons and holes is as high as 9 × 1013/cm[2] and 4 × 1013/cm[2], respectively
The temperature dependences of the carrier density and mobility are shown in Supplementary Fig. S4
Summary
The wave nature of electrons introduces a small quantum interference correction to resistance known as weak localization[8]. The probability of finding the electron at the original position is determined by interference between partial waves travelling along the closed returning path and its corresponding time-reversal counterpart. Since this quantum interference effect can be suppressed by a magnetic field, the small resistance correction and the phase coherence time can be experimentally determined. In the low temperature limit below a few Kelvin, the phase decoherence rate has a saturating finite value in epitaxial graphene[11,12,13,14] while its temperature dependence is linear like exfoliated graphene at relatively high temperatures[14,15]. The observed behaviours are consistent with dephasing by spin exchange scattering
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