Charge instabilities of the two-dimensional Hubbard model with attractive nearest neighbour interaction

摘要

Attractivenon-localinteractionsjointlywithrepulsivelocalinteractioninamicroscopicmodellingofelectronicFermiliquidsgenerateacompetitionbetweenanenhancementofthestaticchargesusceptibility–ultimatelysignallingchargeinstabilityandphaseseparation–anditscorrelationinducedsuppression.WeanalysethisscenariothroughtheinvestigationoftheextendedHubbardmodelonatwo-dimensionalsquarelattice,usingthespinrotationinvariantslave-bosonrepresentationofKotliarandRuckenstein.Thequasiparticledensityofstates,therenormalisedeffectivemassandtheLandauparameterFs0arepresented,wherebythepositivityofFs0–1constitutesacriterionforstability.VanHovesingularitiesinthedensityofstatessupportpossiblechargeinstabilities.A(negative)next-nearestneighbourhoppingparametert'shiftstheirpositionsandproducesatendencytowardschargeinstabilityevenforlowfillingwhereasthet'-controlledparticle-holeasymmetryofthecorrelationdriveneffectivemassissmall.AregionofinstabilityonaccountoftheattractiveinteractionVisidentified,eitherathalffillingintheabsenceofstrongelectroniccorrelationsor,inthecaseoflargeon-siteinteractionU,atdensitiesfarfromhalffilling...