Spin excitations and magnon fractionalization in a quantum spin ladder

S. Notbohm, Patrick Ribeiro, B. Lake +12 more

David Robinson Clarke, Oleg Tchernyshyov, J.-B. Fouet +1 more

B. Thielemann, Christian Rüegg, Henrik Moodysson Rønnow +12 more

We measure by inelastic neutron scattering the spin excitation spectra as a function of applied magnetic field in the quantum spin-ladder material (C5H12N)2CuBr4. Discrete magnon modes at low fields in the quantum disordered phase and at high fields in the saturated phase contrast sharply with a spinon continuum at intermediate fields characteristic of the Luttinger-liquid phase. By tuning the magnetic field, we drive the fractionalization of magnons into spinons and, in this deconfined regime, observe both commensurate and incommensurate continua.

A. Zheludev, D. Schmidiger, S. Mühlbauer +7 more

Alexandros Metavitsiadis, Christina Psaroudaki, Wolfram Brenig

We identify fingerprints of a proximate quantum spin liquid (QSL), observable by finite-temperature dynamical thermal transport within a minimal version of the idealized Kitaev model on a two-leg ladder if subjected to inevitably present Heisenberg couplings. Using exact diagonalization and quantum typicality, we uncover (i) an insulator-conductor crossover induced by recombination of fractionalized excitations at small Heisenberg couplings, (ii) low- and high-energy signatures of fractionalized excitations, which survive far off the pure QSL point, and (iii) a nonmonotonous current lifetime versus Heisenberg couplings. Guided by perturbation theory, we find (iv) a Kitaev-exchange-induced ``one-magnon'' contribution to the dynamical heat transport in the strong Heisenberg rung limit.

G. Simutis, S. N. Gvasaliya, Fan Xiao +2 more