Spin-½

About: Spin-½ is a research topic. Over the lifetime, 40423 publications have been published within this topic receiving 796639 citations.

Inertia-driven spin switching in antiferromagnets

Abstract: Magnetic switching is typically accomplished by using a driving field that stays on until the magnetization is rotated to its final position. An experiment demonstrates that, in antiferromagnets, inertial effects can be harnessed, such that only a short ‘kick’ is required to transfer sufficient momentum to the spin system for it to reorient. It is generally accepted that the fastest way to reorient magnetization is through precessional motion in an external magnetic field1,2,3,4,5,6,7. In ferromagnets, the application of a magnetic field instantaneously sets spins in motion and, in contrast to the inertial motion of massive bodies, the magnetization can climb over a potential barrier only during the action of a magnetic-field pulse. Here we demonstrate a fundamentally different scenario of spin switching in antiferromagnets, where the exchange interaction between the spins leads to an inertial behaviour. Although the spin orientation hardly changes during the action of an optically generated strong magnetic-field pulse of 100 fs duration, this pulse transfers sufficient momentum to the spin system to overcome the potential barrier and reorient into a new metastable state, long after the action of the stimulus. Such an inertia-based mechanism of spin switching should offer new opportunities for ultrafast recording and processing of magnetically stored information.

The Lightcone Bootstrap and the Spectrum of the 3d Ising CFT

Abstract: We compute numerically the dimensions and OPE coefficients of several operators in the 3d Ising CFT, and then try to reverse-engineer the solution to crossing symmetry analytically. Our key tool is a set of new techniques for computing infinite sums of SL(2, RR ) conformal blocks. Using these techniques, we solve the lightcone bootstrap to all orders in an asymptotic expansion in large spin, and suggest a strategy for going beyond the large spin limit. We carry out the first steps of this strategy for the 3d Ising CFT, deriving analytic approximations for the dimensions and OPE coefficients of several infinite families of operators in terms of the initial data {Δ_σ, Δ_ϵ, f_(σσϵ), f_(ϵϵϵ), c_T}. The analytic results agree with numerics to high precision for about 100 low-twist operators (correctly accounting for O(1) mixing effects between large-spin families). Plugging these results back into the crossing equations, we obtain approximate analytic constraints on the initial data.

Quantizing three-spin string solution in AdS_5 x S^5

Abstract: As was recently found in hep-th/0304255, there exists a simple non-supersymmetric classical solution describing a closed string rotating in S^5 and located at the center of AdS_5. It is parametrized by the angular momentum J of the center of mass and two equal SO(6) angular momenta J' in the two other orthogonal rotation planes. The dual N=4 SYM operators should be scalar operators in SU(4) representations [0,J-J',2J'] or [J'-J,0,J'+J]. This solution is stable if J' > 3/2 J and for large J + 2 J' its classical energy admits an expansion in positive powers of g_eff = \lambda/(J + 2 J')^2: E= J + 2 J' + g_eff J' + ... . This suggests a possibility of a direct comparison with perturbative SYM results for the corresponding anomalous dimensions in the sector with g_eff << 1, by analogy with the BMN case. We conjecture that all quantum sigma model string corrections are then subleading at large J', so that the classical formula for the energy is effectively exact to all orders in \lambda. It could then be interpolated to weak coupling, representing a prediction for the anomalous dimensions on the SYM side. We test this conjecture by computing the 1-loop superstring sigma model correction to the classical energy.