Spin polarization of electron current through a potential barrier in two-dimensional structures with spin-orbit interaction

We show that an initially unpolarized electron flow acquires spin polarization after passing through a lateral barrier in two-dimensional (2D) system with spin-orbit interaction (SOI) even if the current is directed normally to the barrier. The generated spin current depends on the distance from the barrier. It oscillates with the distance in the vicinity of the barrier and asymptotically reaches a constant value. The most efficient generation of the spin current (with polarization above 50%) occurs, when the Fermi energy is near the potential barrier maximum. Since the spin current in SOI medium is not unambiguously defined we propose to pass this current from the SOI region into a contacting region without SOI and show, that the spin polarization loss under such transmission can be negligible.Comment: 11 pages, 6 figures, accepted for publication in Journal of Physics: Condensed Matte

Factorization effects in a model of unstable particles

The effects of factorization are considered within the framework of the model of unstable particles with a smeared mass. It is shown that two-particle cross section and three-particle decay width can be described by the universal factorized formulae for an unstable particles of an arbitrary spin in an intermediate state. The exact factorization is caused by the specific structure of the model unstable-particle propagators. This result is generalized to complicated scattering and decay-chain processes with unstable particles in intermediate states. We analyze applicability of the method and evaluate its accuracy.Comment: 13 pages, 7 figure

Modifications of gravity via differential transformations of field variables

We discuss field theories appearing as a result of applying field transformations with derivatives (differential field transformations, DFT) to a known theory. We begin with some simple examples of DFTs to see the basic properties of the procedure. In this process the dynamics of the theory might either change or conserve. After that we concentrate on the theories of gravity which appear as a result of various DFT applied to general relativity, namely the mimetic gravity and Regge-Teitelboim embedding theory. We review main results related to the extension of dynamics in these theories, as well as the possibility to write down the action of a theory after DFT as the action of the original theory before DFT plus an additional term. Such a term usually contains some constraints with Lagrange multipliers and can be interpreted as an action of additional matter, which might be of use in cosmological applications, e.g. for the explanation of the effects of dark matter.Comment: 18 page