Magnon-bound-state hierarchy for the two-dimensional transverse-field Ising model in the ordered phase

• Spectral properties of the (2+1)(2+1)-dimensional Ising model were investigated.
• Critical amplitude relations for the low-lying levels were calculated.
• Connections with a Z2 gauge theory conjecture and with possible future experiments were made.
• The numerical diagonalization method was employed.
• Corrections to scaling were suppressed by extended interactions.

In the ordered phase for an Ising ferromagnet, the magnons are attractive to form a series of bound states with the mass gaps, m2