dynamic kerr effect responses in the terahertz-range

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1、DynamicKerreffectresponsesintheTerahertz-rangeUliH¨aberleandGregorDiezemannInstitutf¨urPhysikalischeChemie,Universit¨atMainz,Welderweg11,55099Mainz,GermanyDynamicKerreffectmeasurementsprovideasimplerealizationofanonlinearexperiment.Weproposeafield-offexperimentw

2、hereanelectricfieldofoneorseveralsinusoidalcycleswithfrequencyΩisappliedtoasampleinthermalequilibrium.Afterwards,theevolutionofthepolarizabilityismeasured.IfsuchanexperimentisperformedintheTerahertz-rangeitmightprovidevaluableinformationaboutthelow-frequencyd

3、ynamicsindisorderedsystems.WetreatthesedynamicsintermsofaBrownianoscillatormodelandcalculatetheKerreffectresponse.Itisshownthatfrequency-selectivebehaviourcanbeexpected.Intheinter-estingcaseofunderdampedvibrationalmotionwefindthatthefrequency-dependenceoftheph

4、onon-dampingcanbedeterminedfromtheexperiment.Alsothebehaviourofoverdampedrelaxationalmodesisdiscussed.Fortypicalglassymaterialsweestimatethemagnitudeofallrelevantquantities,whichwebelievetobehelpfulinexperimentalrealizations.PACSNumbers:05.40.jc,63.50+x,78.2

5、0.FmI.IntroductionDynamicKerreffectstudieshavebeenutilizedtomonitorthereorientationaldynamicsofsupercooledliquidsforalongtime[1].Insuchexperiments,thetime-dependentpolariz-abilityisobservedafteranelectricfieldhasbeenswitchedonoroff(’fieldon’and’fieldoff’version).I

6、nthecontextofsupercooledliquidsacomparisonofreorientationalcorrelationtimesextractedfromKerreffectdataanddielectricrelaxationshowedthatthecorrelationtimesassociatedwithdifferentLegendrepolynomials(l=2fortheKerreffect,l=1fordielectricrelaxation)areverysimilar[2]

7、.arXiv:cond-mat/0501109v1[cond-mat.soft]6Jan2005InatheoreticaldescriptionofthedynamicKerreffect,thecouplingofthefieldtopermanentdipolemomentsaswellastoinduceddipolemomentshastobetakenintoaccount.Withinarotationaldiffusionmodel,amonoexponentialdecay(’fieldoff’)ora

8、biexponentialrise(’fieldon’)ofthepolarizabilityhasbeenfound[3].AnimportantpropertyoftheKerreffectisitsnonlinearitywithrespecttotheappliedfield.Measurementsofnonlineareffectsgenerallyprovideinformati