Chiral Tunneling in a Twisted Graphene Bilayer

Abstract

The perfect transmission in a graphene monolayer and the perfect reflection in a Bernal graphene bilayer for electrons incident in the normal direction of a potential barrier are viewed as two incarnations of the Klein paradox. Here we show a new and unique incarnation of the Klein paradox. Owing to the different chiralities of the quasiparticles involved, the chiral fermions in a twisted graphene bilayer show an adjustable probability of chiral tunneling for normal incidence: they can be changed from perfect tunneling to partial or perfect reflection, or vice versa, by controlling either the height of the barrier or the incident energy. As well as addressing basic physics about how the chiral fermions with different chiralities tunnel through a barrier, our results provide a facile route to tune the electronic properties of the twisted graphene bilayer.

An integrated diamond nanophotonics platform for quantum-optical networks

“…This approach can further be used to control the timing and the shape of the single-photon pulses (30). Unlike previous demonstrations of Raman tuning of solid-state quantum emitters (31)(32)(33), the tuning range demonstrated here (20) is comparable to the inhomogeneous distribution of the SiV ensemble and can thus be used to tune pairs of SiV centers into resonance. Entanglement of SiV centers in a diamond nanophotonic waveguide.…”

Density of States of Twisted Bilayer Graphene at Low Energy

“…where where is interlayer coupling and ( , ) is two dimensional wave vector relative to the midpoint of the two Dirac Points [9]. The vector ∆ (∆ , ∆ ) is relative shift of the Dirac Points in the Brillouin Zone (BZ) (see Fig.…”

In-plane chiral tunneling and out-of-plane valley-polarized quantum tunneling in twisted graphene trilayer

“…and a ~ 0.246 nm the lattice constant of the hexagonal lattice [13,25]. The displaced Dirac cones and parabolic valleys cross at the intersections and two saddle points (van Hove singularities) at ± E V emerge in the presence of a finite interlayer coupling [29,30], as shown in Fig.…”

“…Obviously, both the massless Dirac fermions and massive chiral fermions coexist in the twisted graphene trilayer, which implies that the trilayer may combine the properties of the twisted monolayer and the Bernal bilayer. In order to elucidate the similarities and differences of the three graphene systems (monolayer, Bernal bilayer, and the twisted trilayer), we calculated chiral tunneling [25,32] For the twisted graphene trilayer, the low-energy Hamiltonian is described by [29] (12)…”

“…In Bernal stacking, the charge carriers of the graphene bilayer have a parabolic energy spectrum and exhibit chirality that resembles those associated with spin 1. However, a twist between the two layers splits the parabolic band touching into two Dirac cones [13][14][15][16][19][20][21][22][23][24] and changes the chirality of the low-energy quasiparticles to those of spin 1/2 [18,25]. This provides a facile route to tune the electronic properties of graphene bilayer.…”