We have studied the spin dependent force and the associated momentum space Berry curvature in an accelerating system. The results are derived by taking into consideration the non relativistic limit of a generally covariant Dirac equation under the presence of electromagnetic field where the methodology of Foldy-Wouthuysen transformation is applied to achieve the non relativistic limit. Spin currents appear due to the combined action of the external electric field, crystal field and the induced inertial electric field via the total effective spin-orbit interaction. In an accelerating frame, the crucial role of momentum space Berry curvature in the spin dynamics has also been addressed from the perspective of spin Hall conductivity. For time dependent acceleration, the expression for the spin polarization has been derived.

We have calculated the Berry phase of Hall particles which are found to remain constant over the filling factor ν in a special arrangement. It has been found that the probability of getting this phase vanishes at ν > 1/5. This is the implication of the crystallization in the Hall fluid after the filling factor ν = 1/6.

We theoretically study the renormalization of inertial effects on the spin dependent transport of conduction electrons in a semiconductor by taking into account the interband mixing on the basis of k. p perturbation theory. In our analysis, for the generation of spin current we have used the extended Drude model where the spin orbit coupling plays an important role. We predict enhancement of the spin current resulting from the rerormalized spin orbit coupling effective in our model in cubic and non cubic crystal. Attention has been paid to clarify the importance of gauge fields in the spin transport of this inertial system. A theoretical proposition of a perfect spin filter has been done through the Aharonov-Casher like phase corresponding to this inertial system. For a time dependent acceleration, effect of k. p perturbation on the spin current and spin polarization has also been addressed. Furthermore, achievement of a tunable source of polarized spin current through the non uniformity of the inertial spin orbit coupling strength has also been discussed.

No abstract

We have studied here the influence of the Berry phase generated due to a cyclic evolution of an entangled state of two spin 1/2 particles. It is shown that the measure of formation of entanglement is related to the cyclic geometric phase of the individual spins.In the last few years Berry phase in a single particle system has been studied very well, both theoretically and experimentally. However, the study of Berry phase in an entangled state has become a topic of interest very recently [1,2,3,4,5]. As entanglement is a striking feature of quantum systems and is a useful resource to realize quantum information, quantum teleportation, quantum cryptography or quantum computation, the study of entangled state has absorbed much attention. We have to be careful about two aspects of Berry phase of an entangled state. One is how it changes due to interparticle interaction [1, 2, 3] and the other is how it affects [4] the biparticle states. The motivation of this letter is to see the effect of the Berry phase on an entangled system of two spin-1/2 particles. As a result we have also found a connection between it and the concurrence (which is the measure of of entanglement) for different spin chains.It is well known that a fermion which is a spin 1/2 particle can be realized when a scalar particle is attached with a magnetic flux quantum. The attachment of the magnetic flux quantum changes the spin and statistics of the scalar particle. The effect of the flux quantum is to induce an appropriate Aharanov-Bohm phase which simulates the statistical phase factor. For one complete rotation the wave function of a fermion acquires an extra geometric phase known as Berry phase besides the dynamical phase. The attachment of magnetic flux quantum to a scalar particle is also equivalent to the motion of a charged particle in the field of a magnetic monopole of strength 2b where b is a half integer or integer. The angular momentum of the particle can be written asThis produces a magnetic field [6]normal to the surface where φ 0 = hc e is the flux quantum and R is the radius of the sphere. For one complete rotation, wave function of the particle will acquire an extra geometric phase as [7]besides the dynamical phase. b is called the Berry phase factor and in this letter we shall show how this factor is related to the concurrence of an entangled state. As b = 1/2 corresponds to one flux quantum, when a scalar field traverses a closed path with one flux quantum, we have the phase as e i2πb = e iπ . In general, the Berry phase acquired by a fermion when it encircles N number of magnetic flux quanta in a closed path is given by e i2πN .To study the Berry phase effect of an entangled system of two spin-1/2 particles (at A and B) we may start with the state describing the two spins in the standard basis as ψ = 1 √ M [a 1 | ↓↓> +a 2 | ↓↑> +a 3 | ↑↓> +a 4 | ↑↑>] (4) * Electronic address: banasri@isical.ac.in