universal behaviour of the superfluid fraction and tc of he-3 in 99.5% open aerogel

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1、UniversalBehaviouroftheSuperfluidFractionandTof3HeinAerogelcG.Lawesa,S.C.J.Kingsleya∗,N.Muldersb,andJ.M.ParpiaaaLaboratoryofAtomicandSolidStatePhysics,CornellUniversity,Ithaca,NY,USA.bDepartmentofPhysicsandAstronomy,UniversityofDelaware,Newark,DL,USA(February1,2008)3Wehaveinve

2、stigatedthesuperfluidtransitionofHeindifferentsamplesofsilicaaerogel.Bycomparingnewmeasurementsona99.5%samplewithpreviousobservationsonthebehaviourof33Hein98%porousaerogelwehavefoundevidenceforuniversalbehaviourofHeinaerogel.Werelateboththetransitiontemperatureandsuperfluiddensi

3、tytothecorrelationlengthoftheaerogel.Thepropertiesofbulk3Hearewellunderstood.Theingtheobservedsuperfluiddensities.extremepurityof3HeatlowtemperaturesmakesitanInthisLetterwepresentdatafromseveraldifferentidealsystemtostudytheagreementbetweentheoreti-experimentson3Heinaerogel,inc

4、ludingnewresultsoncalandexperimentalresultsonnon-conventionalCooper3Heconfinedtoa99.5%porositysample.Thissamplepairingintheabsenceofdisorder.Disorderplaysacru-isafactoroffourmoredilutethananypreviouslyinves-cialroleinsuppressingthepairinginteractioninhightigated[17]andiscrucia

5、lforunderstandingtheevolu-Tsuperconductors,theotherwellestablishednons-tionfrombulk3Hetoaregimewhereimpurityscatter-cwavepairedsystem.Thesuperfluidtransitionof3Heingdominates.Incomparingthesedifferentsamplesweconfinedtoasampleofveryporoussilicaaerogelwasfindevidencethattherelatio

6、nbetweensuperfluidden-firstreportedfouryearsago[1,2].Theaerogelpro-sityandthesuperfluidtransitiontemperatureof3Heinvidesastructuraldisorderbackground[4]totheliquid.aerogelfollowsauniversalbehaviour,independentofthe3Heiscompressible,andthedensitycanbecontinuouslyaerogelsample.Thi

7、sissignificantbecausebothofthesetunedby≈30%whilemaintainingafixeddisorder.Thequantitiesareindividuallysensitivetothemicrostructure3Hezerotemperaturecoherencelengthξ,definedasoftheaerogel,andvarygreatlyfromsampletosample.0ξ0=¯hvf/kBTc,variesfrom180˚Atoover700˚AasaWealsopresentevi

8、dencethatthesuppressionofTccanfunctionofdensity.BecausetheCooperpair