100 lat fizyki niskich temperatur i nadprzewodnictwa

Transkrypt

1 100 lat fizyki niskich temperatur i nadprzewodnictwa Tadeusz Wasiutyński IFJ PAN 9 maja 2013

2 Wstęp teoria BCS teoria Ginzburga Landaua nowe nadprzewodniki wysokotemperaturowe co z tego mamy

3 Heike Kamerlingh Onnes( ) 1913 nagroda Nobla "for his investigations on the properties of matter at low temperatures which led, inter alia, to the production of liquid helium"

4 Heike Kamerlingh Onnes( ) 1913 nagroda Nobla 1908 skroplenie helu

5 Heike Kamerlingh Onnes( ) 1913 nagroda Nobla 1908 skroplenie helu 1911 odkrycie nadprzewodnictwa

6 Heike Kamerlingh Onnes( ) 1913 nagroda Nobla 1908 skroplenie helu 1911 odkrycie nadprzewodnictwa

7 pierwsze cztery dekady 1931 nadprzewodnictwo w stopie (de Haas i Keesom) 1933 efekt Meissnera (Meissner i Ochsenfield) 1935 Fritz i Heinz London zapostulowali: 1 j = A λ ( me ) 1/2 B = B L λ 2 λ L = µ L 0 n s e 2 teorie Bloch, Einstein, Bohr, Brillouin, Born, Feynmann...

8 John Bardeen

9 John Bardeen

10 oddziaływanie elektron-fonon efekt izotopowy H. Fröhlich Phys. Rev (1950): Leon Cooper Phys. Rev (1956): Bound electron Pairs in a Degenerate Fermi Gas

11 oddziaływanie elektron-fonon efekt izotopowy H. Fröhlich Phys. Rev (1950): φ( k 1, k 2 ; r 1, r 2 ) = 1 V ei( k 1 r 1 + k 2 r 2 ) r = r 2 r 1, K = k 1 + k 2, k = ( k 2 k 1 )/2 Leon Cooper Phys. Rev (1956): Bound electron Pairs in a Degenerate Fermi Gas

12 oddziaływanie elektron-fonon efekt izotopowy H. Fröhlich Phys. Rev (1950): φ( k 1, k 2 ; r 1, r 2 ) = 1 V ei( k 1 r 1 + k 2 r 2 ) r = r 2 r 1, K = k 1 + k 2, k = ( k 2 k 1 )/2 χ(r, K ) = e i k r N(K, ɛ(k)) E K + ɛ(k) E dɛ dk d k Leon Cooper Phys. Rev (1956): Bound electron Pairs in a Degenerate Fermi Gas

13 oddziaływanie elektron-fonon efekt izotopowy H. Fröhlich Phys. Rev (1950): φ( k 1, k 2 ; r 1, r 2 ) = 1 V ei( k 1 r 1 + k 2 r 2 ) r = r 2 r 1, K = k 1 + k 2, k = ( k 2 k 1 )/2 χ(r, K ) = e i k r N(K, ɛ(k)) E K + ɛ(k) E dɛ dk d k EF ωd k EF + ωd Leon Cooper Phys. Rev (1956): Bound electron Pairs in a Degenerate Fermi Gas -k EF

14 Bardeen, Cooper, Schriefer Phys. Rev. (1957) T c 0.57 (0) = 2ħω D exp( 2 V ρ(e F ) ) (T ) (0) = 1.74 ( 1 T T c ) 1/2

15 teoria Ginzburga Landaua Zh. Eksper. Theor. Fiz przejście fazowe jest ciagłe parametr porzadku zależy od pola magnetycznego parametr porzadku jest liczba zespolona: ψ( r) = ψ( r) e iθ( r) = ñ s ( r)e iθ( r)

16 teoria Ginzburga Landaua Zh. Eksper. Theor. Fiz przejście fazowe jest ciagłe parametr porzadku zależy od pola magnetycznego parametr porzadku jest liczba zespolona: ψ( r) = ψ( r) e iθ( r) = ñ s ( r)e iθ( r) f = f m ( i q A)ψ 2 + a(t T c ) ψ 2 + 2b ψ 4

17 teoria Ginzburga Landaua Zh. Eksper. Theor. Fiz przejście fazowe jest ciagłe parametr porzadku zależy od pola magnetycznego parametr porzadku jest liczba zespolona: ψ( r) = ψ( r) e iθ( r) = ñ s ( r)e iθ( r) f = f m ( i q A)ψ 2 + a(t T c ) ψ 2 + 2b ψ 4 [ 1 2m ( i q A) 2 + a(t T c ) + 2b ψ 2] ψ = 0 j = iq 2m (ψ ψ ψ ψ ) q2 m ψ 2 A

18 kwantowanie strumienia magnetycznego e 2e2 j = ( θ + A) Ψ m mc 2 Φ = n hc 2e = nφ 0 SQUID: złacze Josephsona: j = j 0 sin(θ 1 θ 2 ) j 0 = e n s Ke Kd j = j 0 sin δ 1 +j 0 sin δ 2 = j cos(δ 1 δ 2 ) δ 1 δ 2 = 2π Φ Φ 0

19 Superconductivity at 100 In the 100 years since the discovery of superconductivity, progress has come in fits and starts. The graphic below shows various types of superconductor sprouting into existence, from the conventional superconductors to the rise of the copper oxides, as well as the organics and the most recently discovered iron oxides. Experimental progress has relied on fortuitous guesses, while it was not until 1957 that theorists were finally able to explain how current can flow indefinitely and a magnetic field can be expelled. The idea that the theory was solved was overturned in 1986 with the discovery of materials that superconduct above the perceived theoretical limit, leaving theorists scratching their heads to this day. In this timeline, Physics World charts the key events, the rise in record transition temperatures and the Nobel Prizes for Physics awarded for progress in superconductivity. superconducting transition temperature, T c (K) Paul Chu and his team break the 77 K liquidnitrogen barrier and discover superconductivity at 93 K in a compound containing yttrium, barium, copper and oxygen, now known as YBCO and Georg Bednorz Heike Kamerlingh Onnes wins John Bardeen, Leeon Cooper and Robert Alexander Müller the race against James Dewar Schrieffer publissh their (BCS) theory, which to liquefy helium (1908), then builds on the ideea of Cooper pairs proposed 1973 discovers zero resistance in the previous yeaar, and describes all the Brian Josephson mercury with Gilles Holst (1911) electrons togethher as one wavefunction The theory prediccts that superconductivity Wander Johannes de Haas and cannot occur muuch above 20 K Willem Keesom discover superconductivity in an alloy 1972 John Bardeen Leon Cooper Robert Schrieffer Walther Meissner and Robert Ochsenfeld discover that magnetic fields are expelled from superconductors. This Meissner effect means 60 that superconductors can be T > T c T < T c levitated above magnets Brothers Fritz and Heinz London make a long-awaited theory breakthrough, 1913 formulating two equations Heike Kamerlingh Onnes that try to describe how superconductors interact with 20 electromagnetic fields Lev Landau 1962 Brian Josephson predicts that a current will pass between two superconductors separated by an insulating barrier. Two of these Josephson junctions wired in parallel form a superconducting quantum 1986 interference device (SQUID) Georg Bednorz (right) and Alexander that can measure very weak Müller (left) find superconductivity at magnetic fields 30 K, over the 20 K limit of BCS theory, and not in a metal, but a ceramic boiling point of liquid nitrogen 2003 Alexei Abrikosov Vitaly Ginzburg 2006 Hideo Hosono and colleagues discover superconductivity in an iron compound. The highest T c found in these materials to date is 55 K 2001 Jun Akimitsu announces that the cheap and simple chemical magnesium diboride (MgB 2) superconducts up to 39 K 1981 Superconductivity is found by Klaus Bechgaard and colleagues in a salt the first organic material to superconduct at ambient pressure. To date the organic superconductor with the highest T c is Cs 3C 60 at 38 K Image credits (left to right): Physics Today Collection/American Institute of Physics/Science Photo Library; Wikimedia Commons; Eye of Science/Science Photo Library; University of Birmingham Consortium on High T c Superconductors/ Science Photo Library; Y Kohsaka/Cornell University/RIKEN; Emilio Segrè Visual Archives/American Institute of Physics/Science Photo Library; Supercond. Sci. Technol

20