低維耦合系統(tǒng)的Peierls相變和光吸收譜.pdf

1、同濟大學博士后學位論文低維耦合系統(tǒng)的Peierls相變和光吸收譜姓名：王沁申請學位級別：博士后專業(yè)：凝聚態(tài)物理指導教師：陳鴻20020601AbstractABSTRACTTheopticalexcitationandnonadiabaticphysicalpropertiesof10W—dimensionalcorrelatedsystemsarechallengingproblemofcondensedmatterphysitsIn

2、thisreport，basedontheunitarytransforrnationsandtheGreen’Sfunctionmethod，thephasediagramandtheinstabilityofPeierlssystemsinthegroundstateshavebeenstudiedMeanwhile，startingfromthecurrentoperatorandapplyingtheretardedGreen’

3、Sfunction，theopticalexcitationandabsorptionhavebeenresearchedTheSSHmodel，theantiferromagneticspinPeierlsmedelandtheextendedHubbardmodelhavebeeninvestigatedrespectivelyTbSSHmodel，thedimerizationgap，theelectronicexcitingsp

4、ectrumandthedensityofstatesofthesystemsarecalculatedTheopticalabsorptionspectrumiSanalyticallyobtainedforthefirsttimeandtheresultagreeswellwiththatofexperimentsOurresuItsshowthatthenonadiabaticeffectsonthedimerizationgap

5、andontheorderparametersaleessentiallydifferentItiSthemostnotablethatthereisadiscontinuousdropinthedimerizationgaponcethephononfrequencychangesfromzerotofiniteThecaleulatedopticalabsorptionandthedensityofstatesdonothaveth

6、einversesquarerootsingularitybuthaveapeakabovethegapedgeandthereexistsasignificanttailbelowthepeakThepeakofoptical—absorptionspectrumisnotdirectlycorrespondingtothedimerizedgapandtheenergygapissmallthantheactivationenerg

7、yoftheoptical—absorption，SOweconeludethatthedimerizationgaDdeterminedconventionallybythemeasurementsofopticalabsorptionSpectrumislargethanthetruegapThen，thephasediagramandthecorrelationpropertiesofthespinPeierlssvstemwit

8、hspinphononcouplinginthegroundstateareinvestigatedThespindimerorderparameterthespincorrelationfunctionsthemeanphononoccupationnumberthespindimerizationgap，andthedensityofstatesareobtainedTheresultsshowthatatsomecriticalv

9、aluethesystembecomesgaplessand也espinPeierlsdimerizationdisappearsTheinversesquarerootsingularityofthedensityofstatesatthegapedgeintheadiabaticcasedisappearsbecauseofthenonadiabaticerectThespincorrelationfunctionsincrease

10、asthespinphononcouplingconstantincreasesbutdecreaseas也ephononfrequencyincreasesLast，usingonedimensionalextendedPeierlsHubbardmodel，opticalabsorptionspectrumandthedensityofstatesofHMMC’Scompoundinnonadiabaticcaseareobtain

11、edFormoregeneralsituationincludingtheCoulombinteractionsintheHamiltonianourtheorygivesagooddescriptionofthenonadiabaticeffeetandchangeofvariousparametersontheopticalabsorptionspectrumThecalculatedopticalabsorptionCOe伍cie

12、ntiSconsistentwellwiththeexperimentobservationThecurvesofsubgapopticalabsorptionspectrumhaveanuniversalsealingformKEYWORDSnonadiabatic，orderparameterelectronphononcoupling，spinphononcoupling，opticalabsorption，dimerizatio