| Čoahkkáigeassu: | The quantum many-body interactions in one-dimensional spin- 1
2
systems are subject to
Tomonaga-Luttinger liquid (TLL) physics, which predict an array of multi-particle excitations that
form continua in momentum-energy space. Here we use inelastic neutron spectroscopy to study the
TLL spin dynamics in SrCo2V2O8, a compound which contains weakly coupled spin- 1
2
chains of Co
atoms, at 0.05 K and in a longitudinal magnetic field up to 9.0 T. The measurements were performed
above 3.9 T, where the ground state N´eel antiferromagnetic (AFM) order is completely suppressed,
and the multi-particle excitations are exclusively of TLL type. In this region and below 7.0 T, the
longitudinal TLL mode – psinon/antipsinon (P/AP) – is unexpectedly well described by a damped
harmonic oscillator (DHO) while approaching the zone center defining the static spin-spin correlations. A non-DHO-type, continuum-like signal is seen at higher fields, but deviations from the
ideal one-dimensional TLL still remain. This change in the P/AP mode coincides with the phase
transition between the longitudinal spin density wave (LSDW) and transverse AFM order. Inside
the LSDW state, the DHO-type P/AP spectral weight increases and the linewidth broadens as the
magnetic order parameter decreases. These results reveal the impact of three-dimensional magnetic
order on the TLL spin dynamics; they call for beyond the mean-field treatment for the interchain
exchange interactions.
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