Competing dimerization patterns in the spin-1/2 fully frustrated bilayer*

We investigate the phase diagram of the Heisenberg model on the 

fully-frustrated bilayer (FFB) lattice with an additional explicit dimerization 

parallel to the layers. The original FFB has proven to be an important 

sign-free simulatable reference system to understand the singlet-triplet phase

transitions of frustrated dimer magnets recently measured in SrCu2(BO3)2 [Larrea Jiménez et al., Nature 592, 370–375 (2021)].

Adding an intralayer dimerization introduces a new tendency to form an intralayer

singlet pattern into the model which is incompatible with the original interlayer

singlet phase, resulting in different adjacent phase transitions. We classify this

new phase diagram and study the fate of the finite temperature critical point

as well as a possible quantum critical end point in this scenario.