Physical review. B./Physical review. B
Repulsive Tomonaga-Luttinger liquid in the quasi-one-dimensional alternating spin- 12 antiferromagnet NaVOPO4
S. S. Islam, Prashanta K. Mukharjee, Pabitra Kumar Biswas⃰, Mark T. F. Telling, Y. Skourski, K. M. Ranjith, M. Baenitz, Yuji Inagaki, Yuji Furukawa, Alexander A. Tsirlin, R. Nath
Abstract
We probe the magnetic field-induced Tomonaga-Luttinger liquid (TLL) state in the bond-alternating spin-$1/2$ antiferromagnetic (AFM) chain compound ${\mathrm{NaVOPO}}_{4}$ using thermodynamic as well as local $\ensuremath{\mu}\mathrm{SR}$ and $^{31}\mathrm{P}$ NMR probes down to mK temperatures in magnetic fields up to 14 T. The $\ensuremath{\mu}\mathrm{SR}$ and NMR relaxation rates in the gapless TLL regime decay slowly following characteristic power-law behavior, enabling us to directly determine the interaction parameter $K$ as a function of the magnetic field. These estimates are crosschecked using magnetization and specific heat data. The field-dependent $K$ lies in the range of $0.4<K<1$ and indicates the repulsive nature of interactions between the spinless fermions, in line with the theoretical predictions. This renders ${\mathrm{NaVOPO}}_{4}$ the first experimental realization of TLL with repulsive fermionic interactions in hitherto studied $S=1/2$ bond-alternating AFM-AFM chain compounds.