An introduction to spin techniques in particle physics is given. Among the topics covered are: helicity formalism and its applications to the decay and scattering of spin-1/2 and spin-1 particles, techniques for evaluating helicity amplitudes (including projection operator methods and the spinor helicity method), and density matrix techniques. The utility of polarization and spin correlations f...

Zigzag graphene nanoribbons (ZGNRs) are antiferromagnetic in the ground state with zero net magnetization due to the compensation of contributions from opposite edges. Uniform deformations (both shear and axial) do not produce magnetization due to symmetry restrictions. However, we report the results of first-principles calculations that predict the induction of spin density waves (SDWs) in ZGN...

We reconsider microscopic grounds for the electric field response and for the phase dynamics ofcharge/spin density waves in pure systems. We suggest transparent and free of lengthy calculations way to derive the local Lagrangian valid at any temperature 0 < T < TMF and for arbitrary electronic spectrum provided it supports the existence of

Spin waves are waves of dynamical magnetization which can be excited in ferromagnetic materials. These waves can be thought of as slow electromagnetic waves. However, electromagnetic waves in a vacuum are described completely by Maxwell’s equations, and spin waves are not. To describe the dynamics of spin waves, one needs to consider the Landau-Lifshitz equation in addition to Maxwell’s equatio...

We give a microscopic derivation of the spin-spin components of the optical potential for elastic scattering of a nucleon from a target with nonzero spin. A realistic nucleon-nucleon interaction containing direct and exchange terms is used to generate a folded nucleon-nucleus potential whose spin-spin components are treated in distorted-wave Born approximation. We show how folding leads to spin...

Classes of spontaneous symmetry breaking at zero and low magnetic fields in single quantum dots (QD’s) and quantum dot molecules (QDM’s) are discussed in relation to the ratio RW between the interelectron Coulomb repulsion and the harmonic confinement, using spin-and-space unrestricted Hartree-Fock calculations. These include Wigner crystallization for RW . 1, and formation of noncrystallized e...

Using first-principles calculations and angle-resolved photoemission, we show that the spin-orbit interaction leads to a strong splitting of the surface-state bands on low-index surfaces of Bi. The dispersion of the states and the corresponding Fermi surfaces are profoundly modified in the whole surface Brillouin zone. We discuss the implications of these findings with respect to a proposed sur...