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
3
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
10
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…
11
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!
26
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
27
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