[16p-S4_201-1~12] 10.2 Fundamental and exploratory device technologies for spin

2:00 PM - 2:15 PM JST(5:00 AM - 5:15 AM UTC)Presentation by Applicant for JSAP Young Scientists Presentation Award

[16p-S4_201-1] Two-Magnon Bound States in S=1 XXZ Spin Chain with Single-Ion Anisotropy

〇Jotaro Kobayashi¹, Kiyohide Nomura¹ (1.Kyushu Univ.)

Keywords:

Two-magnon bound states,One dimentional quantum spin systems,Quantum phase transition

We study two-magnon bound-state excitations in the one-dimensional S = 1 XXZ chain with single-ion anisotropy and their relation to ground-state quantum phase transitions. This model exhibits various quantum phases, including the Haldane, Néel, XY1, XY2, Large–D, and ferromagnetic phases, depending on the exchange anisotropy Δ and the single-ion anisotropy D. Focusing on two representative phase boundaries, we show that the XY1/XY2 phase boundary coincides with the emergence of two-magnon bound states, confirmed analytically by bosonization and conformal field theory and numerically by exact diagonalization. We further demonstrate that the Néel/Haldane phase boundary is also associated with two-magnon bound states, whose finite-size scaling is consistent with the c = 1/2 conformal field theory. While two-magnon bound states have been extensively studied in systems under external magnetic fields or with strong frustration, their appearance in a relatively quantum spin model has rarely been reported. Our results provide new insight into nontrivial bound-state excitations in low-dimensional quantum magnets.