Stripes and the Emergence of Charge $π$-phase Shifts in Isotropically Paired Systems

Abstract: The interplay of spin and motional degrees of freedom forms a key element in explaining stripe formation accompanied by sublattice reversal of local antiferromagnetic ordering in interacting fermionic models. A long-standing question aims to relate pairing to stripe formation, intending to discern the applicability of simple models that observe this phenomenon in understanding cuprate physics. By departing from fermionic statistics, we show that the formation of stripes is rather generic, allowing one to unveil its competition with superfluid behavior. To that end, we use a combination of numerical methods to solve a model of interacting hardcore bosons in ladder geometries, finding that once stripes are formed, either via external pinning or spontaneously, a sublattice reversal ($\pi$-phase shift) of \textit{charge} ordering occurs, suppressing the superfluid weight. Lastly, we show that when the Cooper pairs are not local, as in the attractive Hubbard model with finite interactions, auxiliary-field quantum Monte Carlo calculations show evidence of fluctuating stripes, but these are seen to coexist with superfluidity. Our results corroborate the picture that static stripes cannot be reconciled with pairing, unlike the case of fluctuating ones.