NSLS-II Workshop

March 15, 2004

László Forró

School of Basic Sciences

Ecole Polytechnique Fédérale de Lausanne

Laboratory of Nanostructures and Novel Electronic Materials

Metals Semiconductors

Novelconductors,

bad metals

Our interest in solid state physics

In Nanostructures

Protein

…and in Biomaterials

DNA

Keratocyte Neuron

Protein Protein polymer

Solid State Physics

High Tc sample: Bi2Sr2CaCu2O8

Tc = 91 K

Studied at U4IR

00 0.2

hole per CuO2

Tempe

ratu

re

anti

ferr

omag

neti

c

superconducting

T*

Non-Fermi liquid

Fermi liquid

Phase diagram

Pseudo-gap

Optimallydoped

underdoped overdoped

∆? Goal: to study the superconducting gap

How can we study ∆ (at NSLS)?• Electron in - electron out

– EELS : SC → vacuum keV– Tunnelling : SC → metal meV

• Photon in - electron out– Photoemission eV

• Electron in - photon out– Inverse Photoemission

• Photon in - photon out– Optical reflectivity– Optical transmission meV– Raman scattering

• 300K = 25 meV = 200cm-1 = 6 THz• Low Tc : 3.5x3K = 100 GHz µwave• High Tc : 3.5x100K = 230cm-1 FIR

Our choice

Low Tc 1/τ ≈ 1013 Hz, 2∆ ≈1010 Hz

ω

σ1 σ21/ω

2∆ ω

2∆2∆ω ω

1.r

t

σdc

Total brightness

Total darkness

In transmission it is « easier » !!

refl

ecti

vity

tran

smis

sion

1

0

Reference paper!

2212 100 nm thick single crystal, self-supported over 0.9 mm hole, platinum substrate

Our method:transparent single crystals of Bi2Sr2CaCu2O8

2212 150 nm thick single cystal, self-supported over 0.6 mm hole, contacted for resistivity, sapphire substrate

The first « good » results (from U4IR)

No peak in transmission ratios -> gaplesssuperconductivity!

Forró et al., PRL, 65, 1941 (1990)

Counter-argument for the absence ofthe gap feature: Clean limit

2∆

T>Tc

1/τ

σ1

ω (cm-1)Very small oscillatory strength → Difficult to observe

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 200 400 600 800

ρ ab (m

Ωcm

)

T (K)

Bi2Sr

2Ca

1-xY

xCu

2O

8

p=0.16

0.12

0.096

0.08

0.058

T*

0 100

1 102

2 102

3 102

4 102

5 102

6 102

0 50 100 150 200 250 300

R (Ω

)

T (K)

p = 1bar

0.1

0.01

0.001

Bi2Sr

2CaCu

2O

8+δ

Leaving the « clean limit » by introducingdefects: by electron irradiation, off-stoichiometry, substitution

e.g.: by Oxygen depletion

Infrared transmission of 2212 up to high temperatures (500 °C) (U4IR)

Thermocouple

Gold coated sapphire holder

heater

electrodes

Reference hole φ =0.6 mm2212 sample

Leaving « clean limit »:e-beam induced defects, heattreatment, substitution – still no gap feature!

Mandrus et ak, 70, 2629 (1993)

Cuprates are unconventional, d-wave superconductors!

2zd

)( 2 gte

Recent work: BaVS3correlated d-electron system (on U10A)

Pressure dependence

L. Forró, R. Gaál, H. Berger, P. Fazekas, K. Penc, I. Kézsmárki and G. MihályPhys. Rev. Lett. 85, 1938 (2000).

Phase diagram

Optical conductivity in the infrared rangeambient pressure under pressure

C. Homes, et al. – NSLS U10A beamline (2001-2002)

∆ = 700 K

100 10000

100

200

300

400

500

600

700 p TMI ∆

18 kbar 17 K 260 K 16 kbar 26 K 320 K 15.7 kbar 27 K 390 K 14.6 kbar 31 K 410 K 1 bar 70 K 750 K

σ 1 (Ω

-1cm

-1)

ω (cm-1)

10 K

HP optical cell

Blue bronzePeierls transition at 180 K

Quasi-1D organic CDW conductors2H-NbSe2: a conventionallayered superconductor

Other correlated systems studied (U4IR)

Nanostructures – carbon nanotubes

Hernadi et al., Catalysis Lett. 59, 229 (1997)

Supporter (Alumina, Zeolite)

Catalyticparticles(Fe, Co, Ni…)

Single walled CNTs Multi walled CNTs

Structured Nanotube Filmsby Soft Lithography

1 mM 10 mM

40 mM 50 mM

Kind et al., Langmuir (2000)

Patterned CNT structures

Logic circuit – IBM (Derycke et al, Nanoletters, New York Times (2001)

Flat panel screen

ZnO phosphor(anode)

Mo gate (for pixel control)Nanotube emitters

Back contact

to emitters

(cathode)

Substarte

Glass

Samsung:

4.5" color screen

Choi et al., APL 75, 3129 (1999)

IR microspectroscopy of nanotubes (on U10B)

– Gives local, chemically sensitive information

Example: optical conductivity of aligned ropes of carbon nanotubes

• Pure SWNTs Rope

•Good metallic behavior for E||

Drude fit for E||:ε0 4.71

ωp 7300

γ 1200

•Large anisotropy

R. Gaál et al., in preparation

Parallel olarization

Perpendicular polarization

300 K

Experiment on SWNT ropes

Biomatter

• Insulates like diamond (Broun et al., Nature’98)

• Semiconducts (Porath et al., Nature’2000); Tran et al., Phys.Rev.Lett.’2000).

• Conducts like a metal (Fink et al., Nature’99).

• Superconducts (proximity effect) (Kasumov et al. Science’2001).

Charge Transport in DNA

Aligned bundle of λ-DNA

Self-supportedoriented DNA bundle,

~10µm width

Light polarized ||and ⊥ to the bundle

Coppergrid

0100 200 3000

Wavenumber (cm-1)

100

Tra

nsm

ittan

ce (%

)

400

A broad, localised

mode

No conduction in d.c. limit

the low energy part… (on U12IR)

L. Forró et al., in preparation

Results… (on U10B)

2000 4000 6000500Wavenumber (cm-1)

0

100

Tra

nsm

ittan

ce (%

)

Parallel polarization

Perpendicular polarization

Phonon structure of a protein: their variationcan be used for diagnostic purposes

0

0.2

0.4

Wavenumber (cm-1)4000 2000

Inte

nsit

y

N-H stretch in proteins C-H

stretch in lipids

C=O stretch

in α-helix

PO2stretch

Alzheimer’s plaques are misfol -ded β-amyloid protein.

Alzheimer’s tangles are hyper-phosphorylated tau protein the forms paired helical filaments.

Plaques and tangles are thought to damage surrounding neurons.

Plaques-like structures, by staining, have recently been identified in other organs: liver, pancreas, ovary, testis, thyroid.

Amyloid plaques

Neurofibrillary tangles

20 µm

20 µm

Normal Alzheimer’sAlzheimer’s disease

1800 1500 1300

Wavenumber (cm-1)

Inte

nsit

y(u

.a.)

AD brain byopsis

α-helix

β-sheet Humain cortexhealthy

Alzheimer’s disease

Conformation change of a protein

Cortex AD plaques

140

120

100

80

60

40

20

0

y p

ositi

on [µ

m]

150100500 x position [µm]

0.80

0.75

0.70

0.65

intensity a.u.

Pancreas β-sheets plaques

“You can observe a lot,

just by watching…”

Conclusion

Acknowledgments…G. Williams H. BergerLarry Carr R. Gaal

Lisa Miller A. Radenovic

Laszlo Mihaly A. Kis

C. Homes

D. Mandrus J. Miklossy

M. Martin S. Kasas

I. Kezsmarki

G. Mihaly

N. Barisic

Thank you for your attention