 Award ID(s):
 2038011
 Publication Date:
 NSFPAR ID:
 10309007
 Journal Name:
 New Journal of Physics
 Volume:
 23
 Issue:
 12
 ISSN:
 13672630
 Sponsoring Org:
 National Science Foundation
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We study a generalized quantum spin ladder with staggered long rangeinteractions that decay as a powerlaw with exponent \alpha α .Using large scale quantum Monte Carlo (QMC) and density matrixrenormalization group (DMRG) simulations, we show that this modelundergoes a transition from a rungdimer phase characterized by anonlocal string order parameter, to a symmetry broken N'eel phase. Wefind evidence that the transition is second order. In the magneticallyordered phase, the spectrum exhibits gapless modes, while excitations inthe gapped phase are well described in terms of triplons – bound statesof spinons across the legs. We obtain the momentum resolved spin dynamicstructure factor numerically and find a well defined triplon band thatevolves into a gapless magnon dispersion across the transition. Wefurther discuss the possibility of deconfined criticality in thismodel.

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Charge density waves (CDWs) have been observed in nearly all families of copperoxide superconductors. But the behavior of these phases across different families has been perplexing. In Labased cuprates, the CDW wavevector is an increasing function of doping, exhibiting the socalled Yamada behavior, while in Y and Bibased materials the behavior is the opposite. Here, we report a combined resonant soft Xray scattering (RSXS) and neutron scattering study of charge and spin density waves in isotopically enriched La 1.8 − x Eu 0.2 Sr x CuO 4 over a range of doping 0.07 ≤ x ≤ 0.20 . We find that the CDW amplitude is temperature independent and develops well above experimentally accessible temperatures. Further, the CDW wavevector shows a nonmonotonic temperature dependence, exhibiting Yamada behavior at low temperature with a sudden change occurring near the spin ordering temperature. We describe these observations using a Landau–Ginzburg theory for an incommensurate CDW in a metallic system with a finite charge compressibility and spinCDW coupling. Extrapolating to high temperature, where the CDW amplitude is small and spin order is absent, our analysis predicts a decreasing wavevector with doping, similar to Y and Bi cuprates. Our study suggests that CDW order in allmore »

Abstract A pairdensitywave (PDW) is a superconducting state with an oscillating order parameter. A microscopic mechanism that can give rise to it has been long sought but has not yet been established by any controlled calculation. Here we report a densitymatrix renormalizationgroup (DMRG) study of an effective
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