3 years ago

# Localization and delocalization of fermions in a background of correlated spins.

Tetsuya Takaishi, Kazuhiko Sakakibara, Ikuo Ichinose, Tetsuo Matsui

We study the (de)localization phenomena of one-component lattice fermions in spin backgrounds. The O(3) classical spin variables on sites fluctuate thermally through the ordinary nearest-neighbor coupling. Their complex two-component (CP$^1$-Schwinger boson) representation forms a composite U(1) gauge field on bond, which acts on fermions as a fluctuating hopping amplitude in a gauge invariant manner. For the case of antiferromagnetic (AF) spin coupling, the model has close relationship with the $t$-$J$ model of strongly-correlated electron systems. We measure the unfolded level spacing distribution of fermion energy eigenvalues and the participation ratio of energy eigenstates. The results for AF spin couplings suggest a possibility that, in two dimensions, all the energy eigenstates are localized. In three dimensions, we find that there exists a mobility edge, and estimate the critical temperature $T_{\ss LD}(\delta)$ of the localization-delocalization transition at the fermion concentration $\delta$.

Publisher URL: http://arxiv.org/abs/1808.03419

DOI: arXiv:1808.03419v3

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