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arXiv:1905.11560 · Physical review. B./Physical review. B

Chiral spin liquid with spinon Fermi surfaces in the spin- 1 2 triangular Heisenberg model

Shou-Shu Gong, Wayne Zheng, Mac Lee, Yuan-Ming Lu, D. N. Sheng

Published Dec 16, 2019• 60 citations
arXivHTMLPDF

Abstract

We study the interplay of competing interactions in spin-$\frac{1}{2}$ triangular Heisenberg model through tuning the first- (${J}_{1}$), second- (${J}_{2}$), and third-neighbor (${J}_{3}$) couplings. Based on a large-scale density-matrix renormalization group calculation, we identify a quantum phase diagram of the system and discover a gapless chiral spin-liquid (CSL) phase in the intermediate ${J}_{2}$ and ${J}_{3}$ regime. This CSL state spontaneously breaks time-reversal symmetry with finite scalar chiral order, and it has gapless excitations implied by a vanishing spin triplet gap and a finite central charge on the cylinder. Moreover, the central charge grows rapidly with the cylinder circumference, indicating emergent spinon Fermi surfaces. To understand the numerical results we propose a parton mean-field spin-liquid state, the $U(1)$ staggered flux state, which breaks time-reversal symmetry with chiral edge modes by adding a Chern insulator mass to Dirac spinons in the $U(1)$ Dirac spin liquid. This state also breaks lattice rotational symmetries and possesses two spinon Fermi surfaces driven by nonzero ${J}_{2}$ and ${J}_{3}$, which naturally explains the numerical results. This realizes an example of a gapless CSL state with coexisting spinon Fermi surfaces and chiral edge states, demonstrating the rich family of interesting quantum phases emergent from competing interactions in triangular-lattice magnets.

DOI
10.1103/physrevb.100.241111

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