Spin-½

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

Parafermionic edge zero modes inZn-invariant spin chains

Abstract: A sign of topological order in a gapped one-dimensional quantum chain is the existence of edge zero modes. These occur in the Z2-invariant Ising/Majorana chain, where they can be understood using free-fermion techniques. Here I discuss their presence in spin chains with Zn symmetry, and prove that for appropriate couplings they are exact, even in this strongly interacting system. These modes are naturally expressed in terms of parafermions, generalizations of fermions to the Zn case. I show that parafermionic edge zero modes do not occur in the usual ferromagnetic and antiferromagnetic cases, but rather only when the interactions are chiral, so that spatial-parity and time-reversal symmetries are broken.

Collective Electron Specific Heat and Spin Paramagnetism in Metals

Abstract: In two previous papers expressions have been obtained for the susceptibility and specific heat of free electrons in forms appropriate for low and high temperatures. With slight interpolation these expressions are adequate to give the temperature variation over the whole temperature range. The results are given in such a form that they are also applicable to electrons not strictly free, as long as the number of states per unit energy range in the unfilled energy band involved is proportional to the square root of the energy, as for free electrons. In this paper more general expressions are obtained which show how the specific heat and the spin paramagnetism, and their temperature variation, depend on the band form. It is only the low temperature range which will be con­sidered, as usually for metals ordinary temperatures fall well within the “low” range. Although the equivalents of some of the results obtained have been given before, and it has been noticed that there is a relation between the electronic specific heat and the spin paramagnetism, the general question has not been treated in any detail. Expressions are first obtained for collective electrons neglecting interchange interaction effects, and given in a convenient form for application. The difficult question of the sus­ceptibility arising from the “orbital” motion of collective electrons will not here be discussed. The conditions necessary for a very large orbital effect do not usually hold; and for the more strongly paramagnetic metals, which are discussed here, it will be sufficient to consider the spin effect alone.

Linear-response theory of spin Seebeck effect in ferromagnetic insulators

Abstract: We formulate a linear response theory of the spin Seebeck effect, i.e., a spin voltage generation from heat current flowing in a ferromagnet. Our approach focuses on the collective magnetic excitation of spins, i.e., magnons. We show that the linear-response formulation provides us with a qualitative as well as quantitative understanding of the spin Seebeck effect observed in a prototypical magnet, yttrium iron garnet.