October 4, 2007

SRC Study on Highly Conductive Polymers (HCP)

Victor Zhirnov, Andrey Kiselev and Ralph Cavin

SRC Forum on Highly Conductive Polymers

2

Brief History

2005 - SRC upon request of several member companies conducted a preliminary investigation on HCP

Seminar provided by Dr. Kevin ShambrookExtensive literature survey

significant body of literature on the topic of HCP foundNo fundamental physics analysis 2005 SRC Study Report

Conclusion: More in-depth study is required before one can conclude that there is a real effect

2007 – Fundamental Study on Critical Assessments of Highly Conductive Polymers

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Very brief summary on HCP

HCP is produced from a conventional polymer film, e.g. polypropylene or polysiloxanes

HCP are reported to exhibit unusual electrical conduction properties

The highest measured current through the HCP film is 1700 A from1cm2 sampleThe resistivity of the HCP film in the direction normal to the surface is ≤10-11 Ohm·cm

for comparison, the resistivity of bulk Cu is 1.7x 10-6 Ohm·cm

It is believed that a special microstructure is developed in the HCP film

Conductive channels of unknown nature

4

Selected PublicationsInstitute of Synthetic Polymeric Materials, Moscow, RussiaN. S. Enikolopyan, et al., Possible Superconductivity near 300-K in Oxidized Polypropylene, JETP LETTERS 49: 371-375 (1989)

“The main aim of the present work is to verify whether or not the low-resistance state in the above experiments can be explained by the formation either metallic or carbon bridge between the contacts HV switching

Bridge formation confirmed

Icrit<100mA

2005-2007Ioffe Physico-Technical Institute, RussiaFreie Universitat Berlin, GermanyA. N. Ionov et al, High Conductivity and Supercurrent in Superconductor-Polymer-Superconductor Systems, Physica B (2005) 506

Ioffe Physico-Technical Institute, RussiaFreie Universitat Berlin, GermanyA. N. Ionov et al, Local distribution of high-conductivity regions in polyamide thin films, JEPT Lett. (2007) 636

Experiments with superconductive electrodes indicate the non-

dissipative transport of charge carriers in the polymers

1989Ioffe Physico-Technical Institute, St.-Petersburg, RussiaA. N. Ionov et al, Low-Resistance State in Polydipheylenephtalide at Low Temperature, Solid State Com. 82, 609 (1992)

1992

Bar-Ilan University, IsraelShlimak I, Martchenkov V, Switching phenomena in elastic polymer films, SOLID STATE COM. 107 (1998): 443-446

1998

Metallic bridge formation from electrode material is

the cause of low-resistance state

LV switchingNo bridge formation

Icrit>2 A

5

Shlimak I, Martchenkov V, Switching phenomena in elastic polymer films, SOLID STATE COMMUNICATIONS 107 (9): 443-446 1998

“The main aim of the present work is to verify whether or not the low-resistance state in the above experiments can be explained by the formation either metallic or carbon bridge between the contacts

High voltage switching Low voltage switching (ultraswitching)

Conclusion: “Ultraswitching” (US) is a new effect, which can not be explained in terms of conventional breakdown. Further investigation is needed to throw light on the nature of conducting filaments in the US ON state

Two switching regimes were found:

Bridge formation

Imax<100mA – limited by bridge melting

No bridge formation

Imax>2 A – limited by electrode burnout

No heating in polymer film

RON~0.5 Ohm=Rcont+Rfilm

6

Conductivity switching in polymers

Polymer Memory

Vsw=2-5 VTsw<μsRon=100-1000 OhmSwitching mechanism not understood

HCP

Vsw~1 VTsw~30000 sRon~0.5 OhmSwitching mechanism not understood

Another conductivity

switching phenomenon

7

Cryogenic experiments

A. N. Ionov et al, High Conductivity and Supercurrent in Superconductor-Polymer-Superconductor Systems, Physica B (2005) 506

Experiments with superconductive electrodes indicate the non-dissipative transport of charge carriers in the polymers

A summary of confirmed data:

Low resistance state at RT

SC state at cryogenic temperatures

What is the RT resistivity?

8

Nikolai Bogdanov-Bel'sky (1895),“Mental counting in a rural school”

The Tretyakov Gallery, Moscow

What does physics have to say?

HCP claim: 10-11 – 10-24 Ohm·cm

Cu: 1.7x 10-6 Ohm·cm

Andrey Kiselev/NCSUKevin Shambrook/Sonoma State URalph Cavin/SRCHarold Hosack/SRCDan Herr/SRCDale Edwards/SRCVictor Zhirnov/SRC Jonathan Dobson

The Study Team:

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Study Group Approach

Regular FxF meetings with the following objectives:

To review publications in the fielda ‘pro et contra’ approach

To review experimental reportssummarize quantitative experimental results reported on highly conductive polymersto address alternative interpretations of experimental results

the role of electrode materials is unclearcontaminations from ambient may contribute to the uncertainty ofmeasurementsConductive bridge formation may be the cause of low-resistance state Bla… bla…

To explore universal mechanisms of electrical conduction in solids, which are applicable to e.g. both normal conductors and superconductors

understanding the fundamentals and developing working hypotheses could help in planning experiments

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ξ=h

2e2=12.9kΩ

T>300K

HCP

√2mαħ

ξ=Don’t believe in this garbage!…

It is impossible!

Can we prove it is impossible?

I’d stay away from such projects-it’s a great way to lose your reputation…

Well,Maybe…

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What is the minimum possible resistivity?

The resistivity of the HCP film in the direction normal to the surface is reported to be 10-11 – 10-24

Ohm·cmfor comparison, the resistivity of bulk Cu is 1.7x 10-6

Ohm·cm

What is the RESISTIVITY of a superconductor?

Textbook picture of SC

12

What is the minimum possible resistivity?

Quantum Transport Limit

Minimal time of dynamical evolution of a physical system

N. Margolus and L. B. Levitin, PhysicaD 120 (1998) 188

EhtΔ

≥Δ22

htE ≥ΔΔPlank’s constant

h=6.62x10-34 Js

Heisenberg’s Energy-time relation

13

Quantum Resistance

A B

Single –electron Conductance channel

R-?

teI

eEV

IRV

Δ=

Δ=

=

Ω=××

⋅×=

==ΔΔ

=

Δ=

Δ

−

−

kC

sJeh

etER

Rt

eeE

9.12)106.1(2

1064.62

219

34

22

0→LΔE

Electron’s charge e=1.6x10-19 C

Ohm’s Law:

14

Summary on Quantum resistance

It was experimentally discovered in the 1980s in Quantum Hall Experiments

2htE ≥ΔΔ

Plank’s constant

h=6.62x10-34 Js

Heisenberg’s Energy-time relation

Ohm’s Law:V=IR

Ω== kehR 9.12

2 2

von Klitzing constant

Nobel Prize in 1985

15

Minimum Resistivity?

( )32

2 ~ atd nn

( )322

2

2

max22

atd nhen

he

⋅=⋅=σ

nCu=8.44x1022 at/cm3

Number of atoms in cross-section

( ) 32

2max

min 21 −== atn

eh

σρ

( )cm⋅Ω⋅= −12min 1072.6ρ

1 cm

1 cm

1 cm

16

Quantum resistance model vs. experiment

What is the RESISTIVITY of a superconductor?

( )cm⋅Ω⋅= −12min 1072.6ρ

Our result:

( )cms ⋅Ω⋅≤ −23106.3ρ

D. J. Quinn and W. B. Ittner, ‘Resistance in a Superconductor’, J. Appl. Phys. 33, 748 (1962):

( )cmCu ⋅Ω⋅= −6107.1ρ

What is wrong with quantum resistance?

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Collective behavior of electrons is a key mechanism for Superconductivity

Dnhe

2

2

max2

⋅=σ

1 cm

1 cm

1 cmElectrons form groups

M - # of electrons in one group

gNh

Me⋅=

2

max)(2σ

Electrons participate in conductance process not individually, but collectively

Ng - # of groups

MnN D

g2=

( ) 322

2

22

2

max22)(2

atDD n

hMen

hMe

Mn

hMe

=⋅=⋅=σ

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Collective Electron Transport: Size Effects of Resistance

72091.807.21E-036.71985E-2319241.02921.29E-181E+11

22797.432.28E-036.71985E-22192410.2921.29E-161E+10

7209.187.21E-046.71985E-211924102.921.29E-141E+09

2279.742.28E-046.71985E-2019241029.21.29E-121E+08

720.927.21E-056.71985E-191924102921.29E-1010000000

227.972.28E-056.71985E-1819241029161.29E-081000000

72.097.21E-066.71985E-171.9241E+101.29E-06100000

22.802.28E-066.71985E-161.9241E+110.00012910000

7.217.21E-076.71985E-151.9241E+120.012931000

2.282.28E-076.71985E-141.9241E+131.292969100

0.727.21E-086.71985E-131.9241E+14129.296910

0.232.28E-086.71985E-121.9241E+1512929.691

Wmin, nmWmin, cmρminNgR0, OhmM

Reported for conventional SC

Rep

orte

d fo

r HC

P

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Resistance with Group Electron Transport

1E-18

1E-16

1E-14

1E-12

1E-10

1E-08

0.000001

0.0001

0.01

1

100

10000

1000000

1 100 10000 1000000 100000000 10000000000 1E+12

M

R0, O

hm

( ) ( ) 31

21

min ~ −⋅ atnMW

The large number in electrons in the group, M, implies minimum width of the conductor to accommodate large M

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Minimum Resistivity of a SC

1 cm

1 cm

1 cm

Electrons form groups

M - # of electrons in one group

( ) 322

2

22

2

max22)(2

atDD n

hMen

hMe

Mn

hMe

=⋅=⋅=σ

AnNM at ⋅==max

( ) 32

2max

min 21 −== atn

Meh

σρ

Total number of electrons in cross-section

( )A

nehNMbal

34

22

−

==ρ

21

Connection between Ballistic Conductance Model and canonical theory of SC

Dnhe

2

2

max2

⋅=σ

1 cm

1 cm

1 cmElectrons form groups

M - # of electrons in one group

gNh

Me⋅=

2

max)(2σ

Electrons participate in conductance process not individually, but collectively

( ) ( ) 31

21

min ~ −⋅ atnMW

The conductive state has a characteristic size of the group (size of quasiparticle):

αξ

m2h

=

The coherence lengthin the Ginzburg-Landau theory of SC

22

Immediate predictions from the ballistic model

R=0

R

Textbook picture of SC

1) The resistance of SC state is a very small but finite value R0

2) The SC “zero-state” resistance depends on the cross-section of the conductor: R0=f(W)

W1

W2<

W3<

Current focus of SC research

Anticipated, but difficult to measure

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Very brief summary on HCP

HCP is produced from a conventional polymer film (e.g. polypropylene or polysiloxanes

HCP are reported to exhibit unusual electrical conduction properties

The highest measured current through the HCP film is 1700 A from1cm2 sampleThe resistivity of the HCP film in the direction normal to the surface is ≤10-11 Ohm·cm

for comparison, the resistivity of bulk Cu is 1.7x 10-6 Ohm·cm

It is believed that a special microstructure is developed in the HCP film

Quasi-one-dimensional conductive paths of unknown nature

The reporte

d data doesn’t seem to

contra

dict to th

e fundamental physi

cs

24

Connection between Quantum Conductance Model and canonical theory of superconductivity

The ballistic model corresponds to temperatures much lower than critical temperature, T<<Tc

temperature does not appear in the model

In the ballistic model, the group of M electrons (quasiparticle) has an characteristic size

the equivalent characteristic size in the canonical theory of superconductivity is the Landau-Ginzburgcoherence length

25

A direct test of the applicability of the ballistic model to superconductivity

The resistivity of the superconducting lead film was reported to be ρ~3.6x10-23 Ohm-cm.

D. J. Quinn and W. B. Ittner, Resistance in a SuperconductorJAP 33 (1962) 748

Superconductivity: Fundamentals and Aplications,by W. Buckel and R. Kleiner (2004 WILEY-VCH)

Material: Pb, nPb=3.3x1022 at/cm3

( )A

nehNMbal

34

22

−

==ρPb film thickness: 1.2 μm;

Width of the cross-section: ~3cm

ρbal=3.4x10-23 Ohm-cm

Almost exactly the experimental number!

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Conclusions from the model

If many-electron coherent transport could be achieved, it would yield conductivity in the range reported for Highly Conductive Polymers

The result of this model doesn’t guarantee the validity of the existence of highly conductive polymers.

Nevertheless, it sends an encouraging message that such systems are in principle possible.

There remain many questions including The structure of the materialTheoretical basis of expectations

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Classical SuperconductivityNo complete theory on superconductors as yet exists. Bardeen-Cooper-Schriffer (BCS) theory help establish a mechanism for superconductors.

Current in a superconductor is made up of electron pairsEach lattice atom is positively charged The first electron pulls the lattice atoms together, making them vibrate

coherently. That, in turn, pulls the following electronInteraction between coherent atom vibrations (phonons) and electrons

causes superconductivity1911 Hg 4.2 K1941 NbN 16.1 K1953 V3Si 17.5 K1973 Nb3Ge 23 K1986 (La1.85Ba.15)CuO4 30 K1987 YBa2Cu3O7 92 K1994 Hg0.8Tl0.2Ba2Ca2Cu3O8.33 138 K 164?2??? ??? ??? ?

Room-Temperature superconductivity?

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Possible theoretical basis

There is an established theory of high-temperature superconductivity in polymers developed by Little and followed up by Ginzburg and others and it is based on an exciton mechanism

the original paper by Little has a very large number of citations

29

30

31

My personal earlier misconceptions about superconductivity

Room temperature superconductivity violates the Laws of Physics

The higher Tc superconductors have lower critical current density Jc

Tc →300 Jc→ 0

These perceptions were not tr

ue

32

CONCLUSIONS

Confirmed data:Low resistance state at RTSC state at cryogenic temperatures

Unconfirmed dataSC state at RT

Experimental Challenge:RT resistivity measurements

There is an established theory of high-temperature superconductivity in polymers

Little, Ginzburg…

33

Comments from an authoritative independent expert in superconductivity

“HCP concepts in view of the science of superconductors”

by Andrey Sergeev, SUNY/Buffalo