Quantum Lifetime Spectroscopy and Magnetotunneling in Double Bilayer Graphene Heterostructures

Abstract

We describe a tunneling spectroscopy technique in a double bilayer graphene heterostructure where momentum-conserving tunneling between different energy bands serves as an energy filter for the tunneling carriers, and allows a measurement of the quasi-particle state broadening at well defined energies. The broadening increases linearly with the excited state energy with respect to the Fermi level, and is weakly dependent on temperature. In-plane magnetotunneling reveals a high degree of rotational alignment between the graphene bilayers, and an absence of momentum randomizing processes.

Ab initio calculations of low-energy quasiparticle lifetimes in bilayer graphene

“…Our calculations of the lifetimes of low-energy QP in undoped BLG are in very good agreement with the measurements in Ref. [7]. Indeed, after subtracting from the experimental results the constant disorder contribution Γ…”

“…A unique insight into these relaxation mechanisms can be gained via energy-resolved measurements such as angle-resolved/time-resolved photoemission spectroscopy [4,5] or scanning tunneling microspcopy/spectroscopy [6]. Another approach has been demonstrated based on momentum-conserving tunneling spectroscopy and recently applied to the study of QP lifetimes in BLG [7], with electron tunneling taking place between two rotationally aligned BLGs separated by a transition-metal dichalcogenide layer. As opposed to a typical device setup with bulk electrodes where the tunneling rate depends directly on the electron density of states in the electrodes, in Ref.…”

“…As opposed to a typical device setup with bulk electrodes where the tunneling rate depends directly on the electron density of states in the electrodes, in Ref. [7] the tunneling rate is dictated by the QP spectral function of the BLGs [7,8], in particular by the corresponding QP energy-broadening Γ. These tunneling spectroscopy measurements reveal several interesting aspects of the decay rate Γ of QPs with energies E within ≈ ±200 meV from the Fermi level (E F ): i) near the Fermi level, Γ(E ≈ E F ) is disorder limited (deduced from its weak temperature dependence), ii) away from E F , electron-electron and/or electronphonon interactions lead to a linear dependence Γ…”

“…Motivated by the experiments in Ref. [7], the goal of this work is to understand the impact of electron-electron interactions on the lifetime of low-energy (|E −E F | < 200 meV) QPs in Bernal BLG, using ab initio calculations. Previous ab initio studies [9][10][11][12][13] of the QP lifetime in BLG and other graphene-related systems were limited to a higher energy range and did not address the low-energy range relevant to transport.…”

“…According to the experiment in Ref. [7], the temperature dependence of the lifetime of low-energy QPs in BLG is very weak, so in this work we focus on the zero temperature case (T = 0). In this case QPs can decay only by emitting (as opposed to absorbing) an e-h pair or a plasmon excitation [18].…”