Li-doped graphene for spintronic applications

Generating spintronic devices has been a goal for the nano science. Here, Li-doped graphene flakes has been suggested for spintronic applications. To aim this goal, density function theory has been used to determine magnetic phases of monolayer and bilayer doped graphene nanoflakes. Adsorption energies, spin polarizations, electronic gaps, magnetic properties and robustness of spin-polarized states have been studied in the presence of dopants and second layers. Based on these results, graphene flakes have been introduced as single molecular magnets and spin amplifiers for room temperature applications. It has been determined that for bilayer flakes with two layers of different sizes, molecular orbitals switch between the layers around the Fermi level. Based on this switch of molecular orbitals in a bilayer graphene flake, spin on/off switches and spintronic memory devices could be achievable

Graphene/Li-Ion battery

Density function theory calculations were carried out to clarify storage states of Lithium (Li) ions in graphene clusters. The adsorption energy, spin polarization, charge distribution, electronic gap, surface curvature and dipole momentum were calculated for each cluster. Li-ion adsorbed graphene, doped by one Li atom is spin polarized, so there would be different gaps for different spin polarization in electrons. Calculation results demonstrated that a smaller cluster between each two larger clusters is preferable, because it could improve graphene Li-ion batteries; consequently, the most proper graphene anode structure has been proposed.Comment: 19 pages, 7 figures, 1 tabl

Quantum nonlinear planar Hall effect in bilayer graphene: an orbital effect of a steady in-plane magnetic field

We study the quantum nonlinear planar Hall effect in bilayer graphene under a steady in-plane magnetic field. When time-reversal symmetry is broken by the magnetic field, a charge current occurs in the second-order response to an external electric field, as a result of the Berry curvature dipole in momentum space. We have shown that a nonlinear planar Hall effect originating from the anomalous velocity is deduced by an orbital effect of an in-plane magnetic field on electrons in bilayer graphene in the complete absence of spin-orbit coupling. Taking into account the symmetry analysis, we derived the dominant dependence of Berry curvature dipole moment on the magnetic field components. Moreover, we illustrate how to control and modulate the Berry curvature dipole with an external planar magnetic field, gate voltage, and Fermi energy

Electronic properties of bilayer graphene in a steady magnetic field

In this thesis, we consider the electronic properties of bilayer graphene in a steady, parallel magnetic field. Using the tight–binding model, and taking into account relevant tight–binding parameters, we find a new contribution to the electronic Hamiltonian describing the orbital effect of the magnetic field. We consider the effect of the magnetic field on the Lifshitz transition, in which the Fermi surface breaks up into separate pockets at very low energy, due to trigonal warping. We show that the predicted band structure is dramatically altered when taking the new magnetic field contribution into account. We consider the effect of the magnetic field on non–linear dynamics in the presence of an ac laser field and spatial inversion asymmetry. Bilayer graphene is particularly interesting from this point of view because inversion symmetry can be broken either through asymmetry of disorder, the presence of a substrate or through interlayer asymmetry induced by an external gate voltage, the latter yielding tunable non–linear properties. Using the Boltzmann transport equation, we determine the intraband contribution to the dc current, known as the magnetic ratchet effect, and the second harmonic current. We also take into account a perpendicular magnetic field component, which produces cyclotron motion and cyclotron resonance. We discuss the dependence of these non–linear currents on the polarisation of light, the direction of the in–plane field, and the cyclotron frequency

Magnetic ratchet effect in bilayer graphene

We consider the orbital effect of an in-plane magnetic field on electrons in bilayer graphene, deriving linear-in-field contributions to the low-energy Hamiltonian arising from the presence of either skew interlayer coupling or interlayer potential asymmetry, the latter being tunable by an external metallic gate. To illustrate the relevance of such terms, we consider the ratchet effect in which a dc current results from the application of an alternating electric field in the presence of an in-plane magnetic field and inversion-symmetry breaking. By comparison with recent experimental observations in monolayer graphene [C. Drexler et al., Nat. Nanotechnol. 8, 104 (2013)], we estimate that the effect in bilayer graphene can be two orders of magnitude greater than that in monolayer graphene, illustrating that the bilayer is an ideal material for the realization of optoelectronic effects that rely on inversion-symmetry breaking

Review on graphene spintronic, new land for discovery

The science for processing and control of electron spins is referred to as “Spintronics”. Metals, semiconductors, and in particular carbon-based materials are especially interesting in this respect due to their spin arrangements. Graphene, a hexagonal two-dimensional structure of carbon has attracted much attention due to its spin relaxation mechanism and many other advantages. We discuss the origin of graphene’s spin in nano-scale devices. A key concept for understanding spin polarized state properties of graphene is Lieb’s theorem, according to which one can predict whether a graphene structure is spin-polarized. However, this theorem cannot predict anything about magnetic properties of graphene. Lieb’s theorem has many important consequences including spin polarization of a supercell, and that quasi-localized states populating complementary sublattices interact with each other. There exists a large number of theoretical works, which study graphene spin polarization using theoretical methods to investigate the magnetic properties of graphene. We will discuss these theoretical works and their important consequences. In addition, several key experimental results for graphene’s spin Engineering are produced