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arXiv · 1908.10877

Two-Magnon Bound States in the Kitaev Model in a $[111]$-Field

Subhasree Pradhan·Niravkumar D. Patel·Nandini Trivedi
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Abstract

It is now well established that the Kitaev honeycomb model in a magnetic field along the $[111]$-direction harbors an intermediate gapless quantum spin liquid (QSL) phase sandwiched between a gapped non-abelian QSL at low fields $H< H_{c1}$ and a partially polarized phase at high fields $H> H_{c2}$. Here, we analyze the low field and high field phases and phase transitions in terms of single- and two-magnon excitations using exact diagonalization (ED) and density matrix renormalization group (DMRG) methods. We find that the energy to create a bound state of two-magnons $\Delta_p$ becomes lower than the energy to create a single spin flip $\Delta_s$ near $H_{c2}$. In the entire Kitaev spin liquid $\Delta_p<\Delta_s$ and both gaps vanish at $H_{c2}$. We make testable predictions for magnon pairing that could be observable in Raman scattering measurements on Kitaev QSL candidate materials.

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Subhasree Pradhan, Niravkumar D. Patel, Nandini Trivedi. 2019-08-28. Two-Magnon Bound States in the Kitaev Model in a $[111]$-Field. https://doi.org/10.1103/physrevb.101.180401

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