Dab tsi yog qhov tshwm sim ntawm superconductivity? Superconductivity yog ib qho tshwm sim nrog xoom hluav taws xob tsis kam thiab tso tawm ntawm cov hlau nplaum sib nqus uas tshwm sim hauv qee cov ntaub ntawv, hu ua superconductors, thaum txias hauv qab qhov kub thiab txias.
Qhov tshwm sim tau pom los ntawm Dutch physicist Heike Kamerling-Onnes lub Plaub Hlis 8, 1911 hauv Leiden. Zoo li ferromagnetism thiab atomic spectral kab, superconductivity yog quantum mechanical phenomenon. Nws yog tus cwj pwm los ntawm cov nyhuv Meissner - ua tiav ejection ntawm magnetic teb kab los ntawm sab hauv lub superconductor thaum nws hloov mus rau lub xeev superconducting.
Qhov no yog qhov tseem ceeb ntawm qhov tshwm sim ntawm superconductivity. Qhov tshwm sim ntawm cov nyhuv Meissner qhia tau hais tias superconductivity tsis tuaj yeem nkag siab yooj yim raws li kev ua kom zoo tshaj plaws ntawm kev coj ua zoo tshaj plaws hauv classical physics.
Dab tsi yog qhov tshwm sim ntawm superconductivity
Cov hluav taws xob tsis kam ntawm cov hlau conductor maj mam txo qis litxo qhov kub thiab txias. Hauv cov khoom siv xws li tooj liab lossis nyiaj, qhov kev txo qis no yog txwv los ntawm impurities thiab lwm yam tsis xws luag. Txawm tias nyob ze rau xoom, tus qauv tiag tiag ntawm tus neeg xyuas pib qhia qee qhov tsis kam. Nyob rau hauv ib lub superconductor, qhov tsis kam poob qis mus rau xoom thaum cov khoom txias hauv qab nws qhov kub thiab txias. Cov hluav taws xob tam sim no los ntawm lub voj ntawm superconducting xaim tuaj yeem khaws cia tsis tu ncua yam tsis muaj lub zog hluav taws xob. Qhov no yog lo lus teb rau lo lus nug, dab tsi yog qhov tshwm sim ntawm superconductivity.
History
Nyob rau xyoo 1911, thaum kawm txog cov khoom ntawm qhov kub thiab txias, Dutch tus kws kho mob Heike Kamerling Onnes thiab nws pab neeg tau pom tias cov hluav taws xob tsis kam ntawm mercury poob rau xoom qis dua 4.2 K (-269 ° C). Qhov no yog thawj zaug pom ntawm qhov tshwm sim ntawm superconductivity. Feem ntau cov ntsiab lus tshuaj ua superconducting ntawm qhov kub txaus.
Tsuas yog qhov ntsuas kub tseem ceeb, cov ntaub ntawv dhau mus rau hauv lub xeev superconducting, yam ntxwv los ntawm ob lub ntsiab lus: ua ntej, lawv tsis tiv thaiv qhov kev hla ntawm hluav taws xob tam sim no. Thaum tsis kam poob mus rau xoom, tam sim no tuaj yeem ncig hauv cov khoom tsis muaj zog dissipation.
Thib ob, yog tias lawv tsis muaj zog txaus, cov hlau nplaum sab nraud tsis nkag mus rau lub superconductor, tab sis tseem nyob ntawm nws qhov chaw. Qhov kev tshem tawm qhov tshwm sim no tau dhau los ua lub npe hu ua Meissner effect tom qab nws tau pom thawj zaug los ntawm tus kws kho mob hauv xyoo 1933.
Peb lub npe, peb tsab ntawv thiab qhov kev xav tsis tiav
Ib txwm physics tsis muab txausCov lus piav qhia ntawm lub xeev superconducting, nrog rau lub hauv paus quantum txoj kev xav ntawm lub xeev cov khoom, uas txiav txim siab tus cwj pwm ntawm electrons cais los ntawm tus cwj pwm ntawm ions nyob rau hauv ib tug siv lead ua lattice.
Tsuas yog xyoo 1957, peb tus kws tshawb fawb Asmeskas - John Bardeen, Leon Cooper thiab John Schrieffer tau tsim cov kev xav ntawm microscopic ntawm superconductivity. Raws li lawv txoj kev xav BCS, cov khoom siv hluav taws xob sib koom ua ke los ntawm kev sib cuam tshuam nrog cov lattice vibrations (hu ua "phonons"), yog li tsim Cooper khub uas txav tsis muaj kev sib txhuam hauv cov khoom. Ib qho khoom tuaj yeem raug saib raws li lub lattice ntawm cov ions zoo rau hauv huab ntawm electrons. Thaum ib qho hluav taws xob dhau los ntawm lub lattice, cov ions txav me ntsis, raug nyiam los ntawm cov hluav taws xob tsis zoo. Qhov kev txav no ua rau thaj chaw muaj hluav taws xob zoo, uas tig mus rau lwm qhov hluav taws xob.
Lub zog ntawm kev sib cuam tshuam hauv hluav taws xob yog qhov tsis muaj zog, thiab cov vapors tuaj yeem tawg tau yooj yim los ntawm thermal zog - yog li superconductivity feem ntau tshwm sim ntawm qhov kub thiab txias. Txawm li cas los xij, BCS txoj kev xav tsis muab ib qho kev piav qhia rau lub neej ntawm high-temperature superconductors nyob ib ncig ntawm 80 K (-193 ° C) thiab saum toj no, rau lwm yam electron-binding mechanisms yuav tsum koom nrog. Daim ntawv thov ntawm qhov tshwm sim ntawm superconductivity yog raws li cov txheej txheem saum toj no.
Kub
Xyoo 1986, qee cov khoom siv ceramic-perovskite tau pom tias muaj qhov kub siab tshaj 90 K (-183 ° C). Qhov kub ntawm qhov sib txuas no yog theoreticallytsis yooj yim sua rau cov pa superconductor, ua rau cov ntaub ntawv raug xa mus rau qhov kub-kub superconductors. Muaj cov cua txias ua kua nitrogen boils ntawm 77 K, thiab yog li superconductivity ntawm qhov kub siab tshaj qhov no ua rau muaj ntau yam kev sim thiab kev siv uas tsis tshua muaj txiaj ntsig ntawm qhov kub thiab txias. Qhov no yog cov lus teb rau lo lus nug ntawm qhov kub thiab txias qhov tshwm sim ntawm superconductivity tshwm sim.
Kev faib tawm
Superconductors tuaj yeem faib ua ntau yam raws li peb qhov kev txaus siab rau lawv lub cev lub cev, ntawm kev nkag siab peb muaj txog lawv, nws kim npaum li cas kom txias rau lawv, lossis ntawm cov khoom uas lawv tsim los ntawm.
Los ntawm nws cov khoom sib nqus
Type I superconductors: cov uas tsuas muaj ib qho tseem ceeb, Hc, thiab hloov pauv sai sai ntawm ib lub xeev mus rau lwm qhov thaum nws mus txog.
Type II superconductors: muaj ob qhov chaw tseem ceeb, Hc1 thiab Hc2, ua cov superconductors zoo meej nyob rau hauv qhov chaw tseem ceeb (Hc1) thiab tag nrho tawm hauv lub xeev superconducting saum toj kawg nkaus (Hc2), nyob rau hauv ib qho kev sib xyaw ntawm lub xeev. cov teb tseem ceeb.
Raws li peb nkag siab txog lawv
Ordinary superconductors: cov uas tuaj yeem piav qhia tag nrho los ntawm BCS txoj kev xav lossis cov kev xav cuam tshuam.
Unconventional superconductors: cov uas tsis tuaj yeem piav qhia siv cov kev xav, piv txwv li: hnyav fermionicsuperconductors.
qhov kev ntsuas no tseem ceeb vim tias BCS txoj kev xav tau piav qhia cov khoom ntawm cov khoom siv hluav taws xob zoo li qub txij li xyoo 1957, tab sis ntawm qhov tod tes, tsis muaj qhov kev xav txaus siab los piav qhia qhov tsis sib xws ntawm superconductors. Feem ntau, Hom I superconductors muaj ntau, tab sis muaj qee qhov kev zam, xws li niobium, uas yog ob qho tib si thiab hom II.
Los ntawm lawv qhov kub thiab txias
Tsis kub superconductors, lossis LTS: cov uas nws qhov kub thiab txias qis dua 30 K.
High kub superconductors, lossis HTS: cov uas nws qhov kub thiab txias siab tshaj 30 K. Ib txhia tam sim no siv 77 K raws li kev sib cais los hais txog seb peb puas tuaj yeem txias cov qauv nrog cov kua nitrogen (uas yog boiling point yog 77 K), uas. Nws muaj peev xwm ua tau ntau dua li cov kua helium (ib txoj hauv kev kom ncav cuag qhov kub thiab txias xav tau los tsim cov khoom siv hluav taws xob qis qis).
Lwm cov ntsiab lus
Ib tus superconductor tuaj yeem yog hom I, uas txhais tau hais tias nws muaj ib qho chaw tseem ceeb, saum toj no uas tag nrho cov superconductivity ploj, thiab hauv qab uas cov magnetic teb raug tshem tawm tag nrho los ntawm superconductor. Hom II, lub ntsiab lus nws muaj ob qhov tseem ceeb ntawm qhov uas nws tso cai rau ib feem ntawm qhov chaw sib nqus los ntawm cov ntsiab lus cais. Cov ntsiab lus no hu ua vortices. Tsis tas li ntawd, nyob rau hauv multicomponent superconductors, kev sib xyaw ua ke ntawm ob tus cwj pwm tuaj yeem ua tau. Hauv qhov no, tus superconductor yog hom 1, 5.
Properties
Feem ntau ntawm cov khoom ntawm lub cev ntawm superconductors sib txawv ntawm cov khoom mus rau cov khoom siv, xws li lub peev xwm kub thiab qhov kub thiab txias, qhov chaw tseem ceeb thiab qhov tseem ceeb ntawm qhov tam sim no qhov ntom ntom uas superconductivity tawg.
Ntawm qhov tod tes, muaj chav kawm ntawm cov khoom uas tsis muaj kev ywj pheej ntawm cov khoom siv hauv paus. Piv txwv li, txhua tus superconductors muaj qhov tsis muaj zog kiag li ntawm qhov siv tam sim no, thaum tsis muaj magnetic teb, lossis thaum siv daim teb tsis pub tshaj tus nqi tseem ceeb.
Lub xub ntiag ntawm cov khoom siv thoob ntiaj teb no txhais tau hais tias superconductivity yog ib theem thermodynamic thiab yog li ntawd muaj qee yam khoom tshwj xeeb uas muaj kev ywj pheej ntawm cov ntsiab lus microscopic.
Qhov xwm txheej sib txawv ntawm tus superconductor. Nyob rau hauv cov pa superconductor, cov kua electron tsis tuaj yeem muab cais ua ib tus neeg electrons. Hloov chaw, nws muaj cov khub ntawm electrons hu ua Cooper khub. Qhov kev sib koom ua ke no yog tshwm sim los ntawm lub zog txaus nyiam ntawm cov hluav taws xob uas tshwm sim los ntawm kev sib pauv ntawm phonons. Vim yog quantum mechanics, lub zog spectrum ntawm cov kua ntawm Cooper khub muaj qhov sib txawv ntawm lub zog, uas yog, muaj qhov tsawg kawg nkaus ntawm lub zog ΔE uas yuav tsum tau muab los ua kom muaj zog ua kua.
Yog li ntawd, yog tias ΔE ntau dua lub zog thermal ntawm cov grating muab los ntawm kT, qhov twg k yog Boltzmann tas li thiab T yog qhov kub, cov kua yuav tsis tawg los ntawm cov grating. Yog liYog li, Cooper vapor kua yog superfluid, uas txhais tau hais tias nws tuaj yeem ntws tsis muaj zog.
tus yam ntxwv superconductivity
Nyob rau hauv cov ntaub ntawv superconducting, cov yam ntxwv superconductivity tshwm sim thaum kub T poob qis dua qhov kub tseem ceeb Tc. Tus nqi ntawm qhov kub tseem ceeb no txawv ntawm cov khoom mus rau cov khoom siv. Pa superconductors feem ntau muaj qhov kub thiab txias li ntawm 20 K txog tsawg dua 1 K.
Piv txwv li, cov khoom mercury muaj qhov ntsuas kub tseem ceeb ntawm 4.2 K. Raws li xyoo 2015, qhov kub siab tshaj plaws uas pom tau rau cov khoom siv hluav taws xob zoo tshaj plaws yog 203 K rau H2S, txawm hais tias yuav tsum muaj kev kub siab txog li 90 gigapascals. Cuprate superconductors tuaj yeem muaj qhov kub siab tshaj qhov tseem ceeb: YBa2Cu3O7, yog ib qho ntawm thawj khob superconductors pom, muaj qhov kub thiab txias ntawm 92 K, thiab mercury-based cuprates nrog qhov kub tseem ceeb tshaj 130 K tau pom. tsis paub.
Electron pairing vim phonon exchanges piav qhia superconductivity nyob rau hauv cov pa superconductors, tab sis tsis piav superconductivity nyob rau hauv newer superconductors uas muaj ib tug kub tseem ceeb heev.
Magnetic fields
Ib yam li ntawd, ntawm qhov ntsuas kub qis dua qhov ntsuas kub tseem ceeb, cov khoom siv hluav taws xob superconducting nres superconducting thaum siv cov hlau nplaum sab nraud uas ntau dua.tseem ceeb magnetic teb. Qhov no yog vim Gibbs dawb zog ntawm lub superconducting theem nce quadratically nrog lub magnetic teb, thaum lub zog dawb ntawm cov theem ib txwm yog kwv yees li ntawm ywj siab ntawm lub magnetic teb.
Yog tias cov khoom siv superconducting nyob rau hauv qhov tsis muaj ib daim teb, ces lub zog dawb ntawm lub superconducting theem yog tsawg dua li ntawm cov theem ib txwm, thiab yog li ntawd, rau qee qhov nqi ntawm cov hlau nplaum (feem ntau rau lub square. cag ntawm qhov sib txawv ntawm lub zog dawb ntawm xoom), ob lub zog dawb yuav sib npaug, thiab yuav muaj kev hloov pauv mus rau theem ib txwm muaj. Feem ntau, qhov kub thiab txias dua thiab muaj zog sib nqus ua rau muaj qhov me me ntawm cov khoom siv hluav taws xob superconducting thiab yog li qhov tob dua ntawm kev nkag mus rau London ntawm sab nraud magnetic teb thiab tam sim no. Qhov tob nkag mus ua infinite ntawm lub sijhawm hloov pauv.
Lub cev
Qhov pib ntawm superconductivity yog nrog los ntawm kev hloov pauv sai ntawm ntau lub cev, uas yog lub cim ntawm kev hloov pauv theem. Piv txwv li, lub peev xwm hluav taws xob hluav taws xob yog proportional rau qhov kub ntawm qhov qub (tsis yog superconducting). Ntawm qhov kev hloov pauv ntawm superconducting, nws muaj kev dhia thiab tom qab ntawd nws yuav tsum tsis muaj kab. Ntawm qhov kub thiab txias, nws hloov pauv ntawm e-α / T rau qee qhov α. Tus cwj pwm exponential no yog ib qho pov thawj rau qhov muaj qhov sib txawv ntawm lub zog.
theem hloov
Kev piav qhia ntawm qhov tshwm sim ntawm superconductivity yog heevpom tseeb. Qhov kev txiav txim ntawm kev hloov pauv ntawm superconducting theem tau tham ntev. Kev sim qhia tias tsis muaj kev hloov pauv thib ob, uas yog, latent cua sov. Txawm li cas los xij, nyob rau hauv lub xub ntiag ntawm sab nraud magnetic teb, muaj latent tshav kub vim hais tias lub superconducting theem muaj ib tug qis entropy, qis dua qhov tseem ceeb kub, dua li lub qub theem.
Kev sim ua kom pom cov hauv qab no: thaum lub magnetic teb nce thiab mus dhau qhov chaw tseem ceeb, qhov tshwm sim ntawm kev hloov pauv ua rau qhov kub thiab txias ntawm cov khoom siv superconducting. Qhov tshwm sim ntawm superconductivity tau piav qhia luv luv saum toj no, tam sim no nws yog lub sijhawm los qhia koj qee yam txog cov nuances ntawm qhov tseem ceeb no.
Kev suav ua hauv xyoo 1970 tau pom tias qhov tseeb nws tuaj yeem tsis muaj zog dua li thawj qhov kev txiav txim vim muaj kev cuam tshuam ntawm kev hloov pauv mus ntev hauv thaj chaw electromagnetic. Nyob rau xyoo 1980, nws tau pom zoo siv qhov kev xav tsis sib haum xeeb, uas cov kab hluav taws xob superconductor vortex ua lub luag haujlwm tseem ceeb, tias qhov kev hloov pauv yog qhov thib ob hauv hom II hom thiab thawj qhov kev txiav txim (piv txwv li, latent heat) hauv hom I, thiab hais tias ob cheeb tsam yog sib cais los ntawm tricritical point.
Cov txiaj ntsig tau lees paub zoo los ntawm kev sim hauv computer hauv Monte Carlo. Qhov no ua lub luag haujlwm tseem ceeb hauv kev kawm txog qhov tshwm sim ntawm superconductivity. Txoj haujlwm tseem nyob rau lub sijhawm tam sim no. Lub ntsiab lus ntawm qhov tshwm sim ntawm superconductivity tsis nkag siab thiab piav qhia los ntawm qhov pom ntawm kev tshawb fawb niaj hnub no.
