$^{51}$V NMR Study of a quasi-1D XXZ spin chain system BaCo$_{2}$V$_{2}$O$_{8}$

We present $^{51}$V NMR measurements on the quasi-one-dimensional $S$=1/2 XXZ antiferromagnet BaCo$_{2}$V$_{2}$O$_{8}$ along the chain. The $^{51}$V NMR spectrum shows that the quantum phase transition takes place from the N\'{e}el ordered phase to the incommensurately ordered phase around Tc$_{1}\approx $4 T. In addition, we studied a spin-lattice relaxation rate, 1/T$_{1}$, as a function of temperature and field. Our results are compared to a theoretical prediction and are discussed in terms of a softening of spinons in an external field.