We review the high field ESR study on the spin S = 1/2 quasi one-dimensional (1D) antiferromagnet with Ising-like anisotropy \(\hbox {BaCo}_{\textrm{2}}\hbox {V}_{\textrm{2}}\hbox {O}_{\textrm{8}}\) . The S = 1/2 Ising-like 1D antiferromagnet is one of the most simple examples of the strongly correlated quantum many body system. In the longitudinal magnetic field along the Ising axis, it exhibits field-induced quantum phase transition from the Néel ordered to the quantum critical Tomonaga-Luttinger liquid (TLL) state with unconventional magnetic excitation. Owing to the moderately low transition field \(H_{\textrm{c}}\) = 3.9 T, the TLL physics can be investigated in detail in \(\hbox {BaCo}_{\textrm{2}}\hbox {V}_{\textrm{2}}\hbox {O}_{\textrm{8}}\) by means of various experimental probes. The high field ESR measurements in the terahertz region contribute to reveal the low temperature magnetism in this compound via observation of the magnetic excitation in wide frequency and magnetic field regions.
