费米面研究中的试验方法.ppt

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1、ExperimentalmethodsinfermisurfacestudiesExperimentalmethods:magnetoresistanceanomalousskineffectcyclotronresonancemagneto-acousticgeometriceffectsShubnikow-deHaaseffectdeHaas-vanAlpheneffectdeHaas-vanAlpheneffectexhibitsverywellthecharacteristicperiodicityin1/Bofthepropertiesofametalinau

2、niformmagneticfield.Quantizationoforbitsinamagneticfieldthekineticmomentum:thepotentialmomentum:(22)(23)Quantizationoforbitsinamagneticfield(24)Theequationofmotionofaparticleofchargeqinamagneticfieldis(25a)Thusoneofthepathintegralsin(24)is(25b)Theotherpathintegralin(24)isQuantizationofor

3、bitsinamagneticfield(25c)Thus(26)Thetotalmagneticflux(27)Quantizationoforbitsinamagneticfield(28)Itfollowsthat(29)(30)QuantizationoforbitsinamagneticfieldTheareasareequalwhen(31)Equalincrementsof1/Breproducesimilarorbits.ThepopulationoforbitsonorneartheFermisurfaceoscillatesasBisvaried,c

4、ausingawidevarietyofeffects.DeHaas-vanAlphenEffectThedeHaas-vanAlpheneffectistheoscillationofthemagneticmomentofametalasafunctionofthestaticmagneticfieldintensity.Theeffectcanbeobservedinpurespecimensatlowtemperaturesinstrongmagneticfields.foratwo-dimensional(2D)system(absolutezero):Thea

5、reabetweensuccessiveorbits:(32)DeHaas-vanAlphenEffectThenumberoffreeelectronorbitalsthatcoalesceinasinglemagneticlevelis(33)SuchamagneticleveliscalledaLandaulevel.DeHaas-vanAlphenEffectLandaulevelthetotalenergyoftheelectronsraisedDeHaas-vanAlphenEffectAllowedelectronorbitalsintwodimensio

6、nsTheangularpositionofthepointshasnosignificanceAmagneticfieldnomagneticfieldTheareabetweensuccessivecircles：Theareaoftheadjacentcircle:DeHaas-vanAlphenEffectasystemofNelectronsatabsolutezeropartlyfilledentirelyfillednofilledFermilevelmovesdowntothelevelsLandaulevelWhens+1isvacated,theFe

7、rmilevelmovesdownabruptlytothenextlowerlevels.DeHaas-vanAlphenEffectTheelectrontransfertolowerLandaulevelscanoccurbecausetheirdegeneracyDincreasesasBisincreased.AsBisincreasedthereoccurvaluesofBatwhichthequantumnumberoftheuppermostfilledleveldecreasesabruptlybyunity.Atthe