Condensed Matter Physics CEG - Science and microwaves26th Jan 2004 Electronic properties of HTS and...

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



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



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



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



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



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



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



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



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



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



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



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



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

Condensed Matter Physics CEG - Science and microwaves26th Jan 2004 Electronic properties of HTS and...

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