Functional Integrals for Correlated Electrons

Local Ward identities for collective excitations in fermionic systems with spontaneously broken symmetries

“…, π/a 0 ) and found that our RPA expressions for the spin stiffnesses and susceptibilities reduce to those previously obtained in Refs. [42,43]. We have also shown that the hydrodynamic expression for the magnon velocity c s = J/χ ⊥ does not hold in presence of gapless fermionic excitations, and it must be replaced by c s = J/χ ⊥ dyn .…”

“…In the simpler case of perfect nesting, that is, when ξ k = −ξ k+Q , corresponding to the half-filled particle-hole symmetric Hubbard model, and at zero temperature, expressions for J and χ ⊥ have been derived in Refs. [42,43] for two spatial dimensions, and it is straightforward to check that our results reduce to these in this limit. Moreover, Eqs.…”

Long-range order, bosonic fluctuations, and pseudogap in strongly correlated electron systems

“…In the simpler case of perfect nesting, that is, when ξ k = −ξ k+Q , corresponding to the half-filled particle-hole symmetric Hubbard model, and at zero temperature, expressions for J and χ ⊥ have been derived in Refs. [36,183] for two spatial dimensions, and it is straightforward to check that our results reduce to these in this limit. Moreover, Eqs.…”

“…To separate collective spin fluctuations from the charge degrees of freedom, we fractionalize the electronic fields as [36,37,65,183]…”

Analytical approach for the Mott transition in the Kane-Mele-Hubbard model

“…In this Letter, we include the x and y channels as well. In the t 2 → 0 limit, the model retains the full spin rotation symmetry, and this should be reflected in our choice of interaction representation [30]. The symmetric decomposition η 0 = 1/8, η x,y,z = −1/8 yields the largest symmetry group SU (2) of the interaction such that…”