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CEG - Science and microwaves 26th Jan 2004
Condensed Matter Physics
Electronic properties of HTS and novel superconductors
• Intrinsic Josephson Tunnelling between atomic layers in HTS
Fundamental physics + “blue sky” applications (THz spectroscopy, single-electronand quantum devices)
• microwave properties
Fundamental physics+ immediate applications Close synergy with “Emerging Device Technologies” –EE CMP includes - “Emerging Device Physics”
introduction
CEG - Science and microwaves 26th Jan 2004
Condensed Matter Physics
Intrinsic Josephson Tunnelling between atomic layers in HTS
Birmingham early SQUID measurementsconfirmed electron-pairing in d-wave HTSalso first HTS quantum devices and microwave applications
Cooper pairs
excitations
volts
current
current
volts
2 - energy gap
Ij sin
Intrinsic tunnelling
CEG - Science and microwaves 26th Jan 2004
Condensed Matter Physics
Intrinsic Josephson Junction Tunnelling in BSCCO
C u
R C IC
c
a
b
S u p e rc o n d u c tin g
N o rm a l, In s u la ti n g
S u p e rc o n d u c tin g
S u p e rc o n d u c tin g
N o rm a l, In s u la ti n g
1 2 Å
3 Å
O C a S r B i
• BSCCO-2212 Bi2Sr2CaCu2O8
• electrical anisotropy ~105
• quasi-2d HTc superconductor
• d-wave l =2 Cooper pairs
Energy gap (T,B) ()~ cos2line nodes - gap 0 inter-layer quantum tunnnelling
BSCCO xtal
CEG - Science and microwaves 26th Jan 2004
Condensed Matter Physics
1 2
3 4
I
la rg e m esa
B S C C O -2 21 2 s in g le c ry sta l
m e sas
Vc
Va b
VI
L ayersstu d ied
C u rre n t p a thB SC C O -2212 c rystal
M es am e a s u re d
• BSSCO cleaves atomically flat ~ mm
• Ion beam and chemical photolithography
• 10 – 50 m mesa structures
• 4-point VI measurements
• across 1-50 atomic layers
• atomically defined intrinsic JJs
Mesa structures
CEG - Science and microwaves 26th Jan 2004
Condensed Matter Physics
Birmingham measurements
Intrinsic tunnelling across individual atomic layers
10 Josephson junctions in series
d-wave Cooper pair and quasi-particle tunnelling
4-point IV measurements20 ns resolutiontunnelling dynamics.
-250 0 250 V / mV
I/
mA
3.5
0
-3.5
4.2K
t /ns
-100 0 100 200 300 400
V /
V
0.0
0.2
0.4
0.6
0.8
1.0
1.2
t /ns
-100 0 100 200 300 400
I /m
A
-10
0
10
20
30
40
Measurement expertise
x
xx
x
x
CEG - Science and microwaves 26th Jan 2004
Condensed Matter Physics
Future - quantum physics of atomically-defined structures
Intrinsic single-electron array devicesIntrinsic Coulomb-blockade array structuresQuantum coherence/computing – Q-bits
Also THz spectroscopy (ac Josephson)
~ 100 nm HTS mesa (FIB -Nature + Nano-technology in Engineering)
1 nm
Quantum devices
Charging energy e2/2C >> kT
Resistance/junction > Rquantum = h/e2
CEG - Science and microwaves 26th Jan 2004
Condensed Matter Physics
Spintronics on individual atomic layerswith Chris Muirhead and Mark Colclough
Spintronics(2)
V
Measure changes in Tc and Josephson current on the top atomic plane
CEG - Science and microwaves 26th Jan 2004
Condensed Matter Physics
Birmingham facility is unique
Very high resolution/sensitivity
MHz - 40 GHz
50 mK to room temperature
B up to 16T
Low T - Tc often ~ 1KHigh B - Hc2 often ~ 10T
Microwave physics -HTS and other novel s/c existing 5-year portfolio programme CEG, Dr Rod Ormeno and Tim Barraclough
Microwaves
CEG - Science and microwaves 26th Jan 2004
Condensed Matter Physics
What do microwaves tell us?
Complex conductivity = 1 + i 2
“normal” electrons s/c electrons
Penetration and losses
B(r) ~ exp(-x/wave penetration and losses
CEG - Science and microwaves 26th Jan 2004
Condensed Matter Physics
Novel dielectric resonator and typical data
R s /R n
Xs/Rn
0
0.2
0.4
0.6
0.8
1
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
4GHz8GHz10GHz15GHz
Rs /
Rn
Temperature (K)
-0.1
0
0.1
0.2
0.3
0.4
0.5
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
4GHz8GHz10GHz15GHz
X
s / R
nTemperature (K)
15 G H z
10
15 G H z
10
84 G H z
8
4 G H z
Sr2RuO4 p-wave s/c
Cavity measurements
Position and width to 50Hz in 10GHz
0 1K
Measure resonant frequency shifts andQ-values - sub 1mm single crystals
CEG - Science and microwaves 26th Jan 2004
Condensed Matter Physics
novel materials -novel pairing- novel physics
heavy fermionsUPt3
, CeCoIn5 pairing ?
Strontium Ruthenatep-wave
HTc d-wave pairing
Organic s/c-(ET)2Cu(SCN)2
pairing ?
MgB2 Tc~38Ks-wave, but 2 energy gaps
Also conventional s/c
Tmeas < 1K
h > kT
B measurements
Novel materials
CEG - Science and microwaves 26th Jan 2004
Condensed Matter Physics
EE - Emerging Device Technologies Group Prof Mike Lancaster, Dr Tim Jackson, Dr Anton Velichko + 4 others
Close synergy in researchnon-linear properties, spin-injection tuning of filters,
ferrites, ferro-electrics,dielectricscontinued collaboration involving frontier physics
EPSRC views collaboration as a major Birmingham strength
Birmingham Microwave programme Physics - fundamental science
Electrical Engineering – applications
filters for mobile communicationsfront-end filters for radio astronomy - Jodrell Bank
Telescopedelay lines and signal processing
tuneable filters with ferroelectrics
Synergy with EE
CEG - Science and microwaves 26th Jan 2004
Condensed Matter Physics