Structure of Matter – WS13/14 – van Loosdrecht – Lecture 10 1

Structure of Matter The Solid State

WS 2013/14

Lectures (Tuesday & Friday)

Paul van Loosdrecht Optical Condensed Matter Physics, II. Physikalisches Institut

pvl@ph2.uni-koeln.de

Website II. Physikalisches Institut www.ph2.uni-koeln.de

http://www.ph2.uni-koeln.de/527.html

Structure of Matter – WS13/14 – van Loosdrecht – Lecture 10 2

Last time: Semiconductor devices

Today:

Superconductivity Your questions

Structure of Matter – WS13/14 – van Loosdrecht – Lecture 10 3

Superconductivity

Heike Kamerlingh Onnes

Nobel prize 1913 (Low T research including liquid He)

PhD RUG on ‘new proof for the rotation of the earth’

1911, Leiden

Discovery of

Superconductivity

1912: disappears

at high currents or

applied magn. fields

Structure of Matter – WS13/14 – van Loosdrecht – Lecture 10 4

Is zero resistance enough?

temperature

resi

stiv

ity

“ideal metal” T

5

T

Res

idual

resi

stiv

ity

“impure metal”

Ideal metal has zero resistance at T=0K

(no xtal imperfections, impurities

or phonons)

Also in shubnikov-de haas effect

Zero resistance (no scattering possible)

J. P. Freire et al, Braz. J. Phys. 34 (2004)

GaAs/AlGaAs

Heterostructure

Structure of Matter – WS13/14 – van Loosdrecht – Lecture 10 5

Meissner Ochsenfeld effect (1933)

Superconductor is also a

perfect diamagnet.

Structure of Matter – WS13/14 – van Loosdrecht – Lecture 10 6

Type I and II Type I: destruction of superconductivity upon applied magnetic field

by first order phase transition

Type II: At first critical field: flux penetration, superconductivity

destroyed at second critical field

YBCO vortex state

(decorated)

Structure of Matter – WS13/14 – van Loosdrecht – Lecture 10 7

BCS Theory (1957) Bardeen, Cooper & Schrieffer: condensation of Cooper pairs

Electrons ‘bind’ together through lattice polarization

bosons condensation energy gap for excitations

Nobel prize 1974

Structure of Matter – WS13/14 – van Loosdrecht – Lecture 10 8

Flux quantization

15

0 ~ 2 10 V s2

h

e

Earth’s magnetic field ~ 500 mG, so in 1 cm2 of BEarth there are ~ 2 million φ0’s.

0B dA n

Total flux (field*area) is integer multiple of φ0

Structure of Matter – WS13/14 – van Loosdrecht – Lecture 10 9

SQUID

∆𝜑 𝐵 + ∆𝜑 𝐼 = 𝑛 ∙ 2𝜋

Structure of Matter – WS13/14 – van Loosdrecht – Lecture 10 10

1986, start of a new era on superconductivity

Bednorz & Muller, nobel prize 1987

Structure of Matter – WS13/14 – van Loosdrecht – Lecture 10 11

High Tc superconductors

Structure of Matter – WS13/14 – van Loosdrecht – Lecture 10 12

The perovskite superconductors

(La,Ba)2CuO4 (Tc=38 K) TlBa2Ca2Cu3O9+d (Tc=123 K)

CuO planes

Structure of Matter – WS13/14 – van Loosdrecht – Lecture 10 13

Applications

Yamanashi XML01 train

581 km/h

Medical imaging (soft tissue, MRI)

Structure of Matter – WS13/14 – van Loosdrecht – Lecture 10 14

Applications

Power transmission lines

Telecommunication filters

Accelerators