Universal scaled Higgs-mass gap for the bilayer Heisenberg model in the ordered phase

Understand

The spectral properties for the bilayer quantum Heisenberg model were investigated with the numerical diagonalization method.

• In the ordered phase, there appears the massive Higgs excitation embedded in the continuum of the Goldstone excitations.
• Recently, it was claimed that the properly scaled Higgs mass is a universal constant in proximity to the critical point.
• Diagonalizing the finite-size cluster with $N \le 36$ spins, we calculated the dynamical scalar susceptibility $\chi_s"(\omega)$, which is rather insensitive to the Goldstone mode.