Order parameters represent a fundamental resource to characterize quantum matter. We show that pair superfluids can be rigorously defined in terms of a nonlocal order parameter, named odd parity, which derivation is experimentally accessible by local density measurements. As a case of study, we first investigate a constrained Bose-Hubbard model at different densities, both in one and two spatial dimensions. Here, our analysis finds pair superfluidity for relatively strong attractive interactions. The odd parity operator acts as the unique order parameter for such phase irrespectively to the density of the system and its dimensionality in regimes of total particle number conservation. In order to enforce our finding, we confirm the generality of our approach also on a two-component Bose-Hubbard Hamiltonian, which experimental realization represents a timely topic in ultracold atomic systems. Our results shed new light on the role of correlated density fluctuations in pair superfluids. In addition, they provide a powerful tool for the experimental detection of such exotic phases and the characterization of their transition to the atomic superfluid phase.
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List of changes
- In the Abstract (line 8): we added the line ", in regimes of total particle number conservation". - End of section 1: we added the lines from 59 to 64, including a new reference (57). - End of section 2.1 (below eq.9): we modified lines 139-143. - Section 3: we added the lines 161-162. - Section 3.1: we modified lines 184-185. - caption figure 3: we added " for finite DMRG". - caption figure 4: we added "by iDMRG simulations". - caption figure 6: we added "performing iDMRG simulations with a maximum bond dimension of χmax = 400."
Nitya Cuzzuol on 2024-09-26 [id 4804]
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