Spin gap in coupled magnetic layers

• Two coupled S=1/2S=1/2 ​quantum spinchains are examined.
• Quasiparticles with generalized spin are introduced.
• Surface effects are eliminated.
• Formation of energy gap is verified.
• Emergence of generalized spin polarization for ground state.

Quantum spinchains are often used to model complex behavior in condensed matter systems that display long range correlations. When two or more quantum spinchains interact, they also exhibit spin transport and model finite nanomagnetic layers. Here, we investigate properties of two coupled S=1/2S=1/2 quantum spinchains in the finite limit, where spurious surface artifacts are present. Our results show the introduction of new fermionic modes with one additional degree of freedom eliminates the artifacts, in an effective one-dimensional finite lattice. In this setting, the mean field approximation is robust and enables the evaluation of energy levels and the energy gap. Moreover, quasiparticle polarization due to interchain coupling is verified and explains the emergence of spin polarization in uniform materials.