BPCB

BPCB was recognized as an outstanding spin ladder model material already back in the 90's. Spin 1/2 antiferromagnetic dimers are weakly coupled in a ladder-like structures, which are in turn well separated from each other. This particular pattern of interactions (strong rung ladder) allows to use a multitude of analytical approximations for both zero field gapped and field-induced gapless phases and the respective dynamic properties. Thanks to the overall low energy scale, the full phase diagram can be accessed and the measured properties can be compared with the theoretical predictions. BPCB has withstood a vast number of tests in this regard.

Some fundamental insights have been achieved in our group by using BPCB as a model material too. In particular, the long-standing predictions of zero-scale universality at z=2 d=1 critical point (or simply at the field that closes the gap) were verified. Also BPCB has turned out to be a good case to study the effect of weak anisotropic interactions in the gapped phase, where they split the spectrum, near the critical points where they create magnonic bound states, and deep in the Luttinger liquid state where they lead to formation of solitonic excitations.