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arXiv · 2002.03529

Complex Phase Diagram of Doped XXZ Ladder: Localization and Pairing

Rong-Yang Sun·Zheng Zhu·Zheng-Yu Weng
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Abstract

How the ground state nature can be dramatically changed by the distinct underlying spin correlation is a central issue of doped Mott insulators. The two-leg XXZ ladder provides a prototypical spin background, which can be tuned from a long-range N\'{e}el order to a short-range ``spin liquid'' via the superexchange anisotropy, giving rise to a complex phase diagram at finite doping. By density matrix renormalization group method, we show that although the charge is always self-localized in the N\'{e}el ordered phase, a second insulating phase emerges, in which the doped holes become paired but remain localized while the transverse spin-spin correlation reduces to short-ranged one to make the N\'{e}el order classical. Only when the N\'{e}el order totally disappears by further reducing anisotropy, does the pairing become truly coherent as characterized by a Luther-Emery state. In sharp contrast, the pairing is totally absent in the in-plane ferromagnetic XXZ regime, where a direct transition from the charge self-localization in the N\'{e}el ordered phase to a Fermi-gas-like state in the spin liquid phase is found. A consistent physical picture is briefly discussed.

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Rong-Yang Sun, Zheng Zhu, Zheng-Yu Weng. 2020-02-10. Complex Phase Diagram of Doped XXZ Ladder: Localization and Pairing. https://doi.org/10.1103/physrevresearch.2.033007

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