APS/A. B. Kuklov et al.
The representation of supersolid in terms of particle (upper panel) or vacancy (lower panel) world lines, with the vertical and horizontal directions standing for the imaginary time and space, respectively. The world lines are “coarse grained” to involve only two discrete elements—sitting on a site and intersite hopping. Periodic boundary conditions are used along both directions. Upper panel: dotted lines mark the most probable particle positions at (seven) sites of the crystalline lattice. Solid blue lines show world lines of (five) particles, with (two) empty sites at any instance of time featuring (two) vacancies. Lower panel: world lines of the (two) vacancies shown by solid red lines. These are obtained from the upper panel configuration by (i) converting the vertical solid blue lines into the dotted blue ones, (ii) replacing the dotted red lines by the solid red lines, (iii) recoloring the horizontal solid segments from blue to red and inverting the direction of motion.