Spin Dynamics in the Bi-Directional Charge Density Wave State of High-T (c) Superconductors

摘要

In this paper, we investigate the dynamical spin susceptibility in the bi-directional charge density wave (BCDW) state by adopting a random-phase approximation. In the BCDW state, we find that no spin resonance exists and only a broad commensurate peak appears for the frequency dependence of the dynamical spin susceptibility at Q = (pi,pi), though a low-energy spin gap feature can also be found as in the superconducting state. While the "hourglass" type of the dispersion for the BCDW state bears some similarities with that in the superconducting state, the momentum distribution of Im chi (+-)(Q,omega) is just the opposite with the incommensurate peaks lying along the diagonal direction for the energy below omega (c) and along the axial direction above omega (c) . In the coexistence of SC and BCDW, the frequency dependence of the dynamical spin susceptibility at Q = (pi,pi) generally shows the two-peak structure, reflecting two energy scales of the spin excitations. These unique features may serve as signatures to verify whether or not the BCDW state is responsible for the formation of the Fermi arcs.