Direct observation of magnon fractionalization in the quantum spin ladder.
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.
Thielemann
B
B
Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institute, CH-5232 Villigen, Switzerland.
Rüegg
Ch
Ch
Rønnow
H M
HM
Läuchli
A M
AM
Caux
J-S
JS
Normand
B
B
Biner
D
D
Krämer
K W
KW
Güdel
H-U
HU
Stahn
J
J
Habicht
K
K
Kiefer
K
K
Boehm
M
M
McMorrow
D F
DF
Mesot
J
J