  Many Mott systems feature a first-order metal-insulator transition at finite
temperatures, with an associated phase coexistence region displaying
inhomogeneities and local phase separation. Here one typically finds "bubbles"
or domains of the respective phases, which are separated by surprisingly thick,
or fat, domain walls, as revealed both by imaging experiments and recent
theoretical modeling. To gain insight into this unexpected behavior, we perform
a systematic model study of the structure of such metal-insulator domain walls
around the Mott point, within the dynamical mean-field theory framework. Our
study reveals that a mechanism producing such "fat" domain walls can be traced
to strong magnetic frustration, which is expected to be a robust feature of
"spin-liquid" Mott systems.
