Topological triplon excitations in a dimerized quantum magnet.

Triplons are triply degenerate spin S = 1 quasiparticles corresponding to the triplet spin excitations of the singlets in a valence bond solid. There are much exotic physics associated with triplon excitations, for instance, bosonic topological insulators states, magnetization plateaus, Bose-Einstein condensation under a magnetic field or rich phase diagrams by applying an external magnetic field and so on. Thus, triplons offer a fertile ground to explore the bosonic excitations and motivate us to search for more hosting materials. In this respect, Na2Cu2TeO6 (NCTO) has come to our attention. Our previous measurements reveal that its ground state may be the singlet state with a gap around 9 meV. Beyond the ground state, the possible topological triplon excitation need to be further studied by inelastic neutron scattering experiments.