2022-2023學(xué)年高二物理競(jìng)賽課件：玻色-愛(ài)因斯坦凝聚

玻色-愛(ài)因斯坦凝聚

玻色-愛(ài)因斯坦凝聚一、理想玻色氣體化學(xué)勢(shì)的性質(zhì)二、Ｎ與基態(tài)粒子數(shù)關(guān)鍵在于當(dāng)時(shí)，將上的粒子數(shù)忽略了.解決辦法:三、矛盾的原因與解決辦法當(dāng)時(shí)，該能級(jí)上的粒子數(shù)與總粒子數(shù)相比，可忽略；而時(shí)，該能級(jí)上的粒子數(shù)是很大的數(shù)值，不可忽略。1.01.00基態(tài)粒子比份T＞TC

彌散態(tài)T＜

TC

凝結(jié)態(tài)T＝

TC

相變點(diǎn)T

0

全部凝結(jié)玻色－愛(ài)因斯坦凝聚2.條件a.玻色子b.隨溫度而改變，且隨溫度降低趨向于01.現(xiàn)象：時(shí)，有宏觀量級(jí)的粒子在零能級(jí)凝聚

玻色凝聚：μ

=0

,n0與n可比

●

●

●

●●●●●●●P=0級(jí)

●

●

●●●●●●●●彌散態(tài)(動(dòng)量空間)凝聚態(tài)動(dòng)量空間的凝聚現(xiàn)象,凝聚體的熵為零，對(duì)壓強(qiáng)無(wú)貢獻(xiàn)四、凝聚相下，內(nèi)能由能量大于0的粒子決定玻色－愛(ài)因斯坦凝聚的實(shí)現(xiàn)(1)LowtemperatureT~10–9(e.g.Rb)

Coolingandtrappingatoms

(2)Higherdensityn~1011-12

Trappingatomsbyusinglaser(3)Systemkeepsinthegasphase

(Non-interaction)

TheNobelPrizeinPhysics1997"fordevelopmentofmethodstocoolandtrapatomswithlaserlight"StanfordUniv.

Stanford,CA,USA

b.1948CollègedeFranceandécoleNornaleSupérieureParis,Franceb.1933NationalInstituteofStandardsandtechnology,MD,USAb.1948Theirresearchishelpingustostudyfundamentalphenomenaandmeasureimportantphysicalquantitieswithunprecedentedprecision.ClaudeCohen-Tannoudji

StevenChu

WilliamD.Phillips1980swhenWilliamPhillipsdevelopednewmethodsofdeceleratingafastatombeam.In1985thefirstreportscamefromexperimentswherethemeanvelocityhadbeenreducedfrom1000m/stozero.DecelerationofAtoms

MOTThemostoftenusedforatomtrapistheMagneto-OpticalTrap(MOT).

StevenChu

usedDopplercoolingwiththreepairsofcounter-propagatinglaserbeams.Atom,regardlessofwhatdirectionitismoving,willencounterafrictionforceandthevelocityspread(andthetemperature)willbereduced

opticalMolasses.Acollectionofsodiumatoms(yellowdotinmiddleofpicture)trappedinaMOT.Lightactsmechanicallyonmaterialobjects,tochangetheirpositionsandvelocities.Laserreducesthevelocityspread(cooling),orconfinetheatoms(trapping).NewcoolingmechanismsExplanationsofthelowtemperatureswerefoundbyClaudeCohen-TannoudjiandbyStevenChu.GreekmythologyhasitthatSisyphusmustendlesslyrollastoneupahillintheUnderworld.Assoonashereachesthetopthestonerollsdownagain.Oneexampleofthenewcoolingmechanismsis

Sisyphuscooling,wheretheconceptsoflightshiftandopticalpumpingplayanimportantrole.

SisyphuscoolingCohen-Tannoudji

developedthefollowingphysicalpicture:10-6KTheatomsmoveonasinusoi-dallymodulatedpotentialsurface,whentheyinteractwithlight(lightshift).Whentheytravel'uphill'theylosespeed.Astheyreachthetopofthe'hill'theyareopticallypumpedtothebottomofa'valley'.Inthiswaytheatomswillalwaystravel'uphill',andthustheirvelocitywillgraduallybereduced.繼續(xù)降溫玻色凝結(jié)TheNobelPrizeinPhysics2001"fortheachievementofBose-Einsteincondensationindilutegasesofalkaliatoms,andforearlyfundamentalstudiesofthepropertiesofthecondensates"EricA.CornellUSAUniversityofColorado,JILA

Boulder,CO,USAb.1961WolfgangKetterleFRG

MIT,

Cambridge,MA,USAb.1957

CarlE.WiemanUSAUniversityofColorado,JILA

Boulder,CO,USAb.1951

Program

GetfirstlyagreatdealofBoseatomswithhighdensityandcooledtemperature(Lasercoolingandtrappingtechnology)Putthesampleinastaticmagneticwell(Magne