Topology of Triplon Bands in the Dimerized Antiferromagnet

Nawa Kazuhiro, Sato Taku J, Tanaka Hidekazu

doi:10.11316/butsuri.78.11_645

<p>Recently, conducting properties of edge/surface modes of some materials are classified by a phase mismatch of electron wavefunctions across a momentum space. The properties of wavefunctions in terms of continuity, which can induce the phase mismatch, are called topology. Topology has attracted interest since it enables classification of systems without local order parameters.</p><p>Recently, the concept of topology has been extended to magnetic quasiparticles, such as magnons and triplons. We measured a dispersion relation of triplon bands in the spin-1/2 dimerized antiferromagnet Ba₂CuSi₂O₆Cl₂ through inelastic neutron scattering experiments. In Ba₂CuSi₂O₆Cl₂, the dimer forms a rectangular lattice with a small distortion, which yields the bond alternation in magnetic interactions. As a result, an energy gap is induced between the bonding the antibonding triplon modes. A spin model realized in Ba₂CuSi₂O₆Cl₂ is interpreted as a triplon variant of Su–Schrieffer–Heeger (SSH) model, indicating that topologically protected edge states are induced by a bipartite nature of the lattice.</p>

Topology of Triplon Bands in the Dimerized Antiferromagnet

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