Normal state resistance and critical current measurement - High-Tc Josephson junction (IEC 61788-22-2:2021)

This part of IEC 61788 is applicable to high-Tc Josephson junctions. It specifies terms,
definitions, symbols and the measurement and estimation method for normal state resistance
(Rn) and intrinsic critical current (Ici), based on a combination of selecting a data set from
measured U–I curves with a geometric mean criterion and fitting a hyperbolic function to that
data set.

Supraleitfähigkeit - Teil 22-2: Messung des Normalleitungswiderstands und des kritischen Stroms - HTS Josephson Kontakt (IEC 61788-22-2:2021)

Mesure de la résistance à l’état normal et du courant critique - Jonction Josephson à Tc élevée (IEC 61788-22-2:2021)

L’IEC 61788-22-2:2021 est applicable aux jonctions Josephson à Tc élevée. Elle spécifie les termes, définitions et symboles, ainsi que la méthode de mesure et d’estimation de la résistance à l’état normal (Rn) et du courant critique intrinsèque (Ici) fondée sur l’association de la sélection d’un ensemble de données à partir des courbes U–I mesurées avec un critère de moyenne géométrique et de l’ajustement d’une fonction hyperbolique à cet ensemble de données.

Merjenje upornosti v normalnem stanju in merjenje kritičnega toka - Spoj "High-Tc Josephson" (IEC 61788-22-2:2021)

Ta del standarda IEC 61788 se uporablja za spoje »High-Tc Josephson«. Določa izraze, definicije, simbole ter metodo za merjenje in ocenjevanje upornosti v normalnem obratovalnem stanju (Rn) in intrinzičnega kritičnega toka (Ici) na podlagi kombinacije izbire niza podatkov iz izmerjenih krivulj U–I s kriterijem geometrijske sredine ter prilagajanja hiperbolične funkcije temu nizu podatkov.

General Information

Status
Published
Publication Date
19-Dec-2021
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
10-Dec-2021
Due Date
14-Feb-2022
Completion Date
20-Dec-2021

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SLOVENSKI STANDARD
SIST EN IEC 61788-22-2:2022
01-februar-2022

Merjenje upornosti v normalnem stanju in merjenje kritičnega toka - Spoj "High-Tc

Josephson" (IEC 61788-22-2:2021)

Normal state resistance and critical current measurement - High-Tc Josephson junction

(IEC 61788-22-2:2021)
Supraleitfähigkeit - Teil 22-2: Messung des Normalleitungswiderstands und des
kritischen Stroms - HTS Josephson Kontakt (IEC 61788-22-2:2021)

Mesure de la résistance à l’état normal et du courant critique - Jonction Josephson à Tc

élevée (IEC 61788-22-2:2021)
Ta slovenski standard je istoveten z: EN IEC 61788-22-2:2021
ICS:
17.220.20 Merjenje električnih in Measurement of electrical
magnetnih veličin and magnetic quantities
29.050 Superprevodnost in prevodni Superconductivity and
materiali conducting materials
SIST EN IEC 61788-22-2:2022 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN IEC 61788-22-2:2022
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SIST EN IEC 61788-22-2:2022
EUROPEAN STANDARD EN IEC 61788-22-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2021
ICS 29.050
English Version
Superconductivity - Part 22-2: Normal state resistance and
critical current measurement - High-T Josephson junction
(IEC 61788-22-2:2021)

Supraconductivité - Partie 22-2: Mesure de la résistance à Supraleitfähigkeit - Teil 22-2: Messung des

l'état normal et du courant critique - Jonction Josephson à Normalleitungswiderstands und des kritischen Stroms -

T élevée HTS Josephson Kontakt
(IEC 61788-22-2:2021)
(IEC 61788-22-2:2021)

This European Standard was approved by CENELEC on 2021-11-25. CENELEC members are bound to comply with the CEN/CENELEC

Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC

Management Centre or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the

same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the

Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2021 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN IEC 61788-22-2:2021 E
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SIST EN IEC 61788-22-2:2022
EN IEC 61788-22-2:2021 (E)
European foreword

The text of document 90/484/FDIS, future edition 1 of IEC 61788-22-2, prepared by IEC/TC 90

“Superconductivity” was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as

EN IEC 61788-22-2:2021.
The following dates are fixed:

• latest date by which the document has to be implemented at national (dop) 2022–08–25

level by publication of an identical national standard or by endorsement

• latest date by which the national standards conflicting with the (dow) 2024–11–25

document have to be withdrawn

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Any feedback and questions on this document should be directed to the users’ national committee. A

complete listing of these bodies can be found on the CENELEC website.
Endorsement notice

The text of the International Standard IEC 61788-22-2:2021 was approved by CENELEC as a

European Standard without any modification.
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SIST EN IEC 61788-22-2:2022
EN IEC 61788-22-2:2021 (E)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments)

applies.

NOTE 1 Where an International Publication has been modified by common modifications, indicated by (mod), the

relevant EN/HD applies.

NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available

here: www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 61788-22-1 - Superconductivity - Part 22–1: EN 61788-22-1 -
Superconducting electronic devices -
Generic specification for sensors and
detectors
IEC 60050-815 2015 International Electrotechnical Vocabulary - - -
Part 815: Superconductivity
IEC 60617 - Graphical symbols for diagrams - -
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SIST EN IEC 61788-22-2:2022
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SIST EN IEC 61788-22-2:2022
IEC 61788-22-2
Edition 1.0 2021-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Superconductivity –
Part 22-2: Normal state resistance and critical current measurement –
High-T Josephson junction:
Supraconductivité –
Partie 22-2: Mesurage de la résistance à l’état normal et du courant critique –
Jonction Josephson à T élevée
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.050 ISBN 978-2-8322-1039-7

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 7 ----------------------
SIST EN IEC 61788-22-2:2022
– 2 – IEC 61788-22-2:2021 © IEC 2021
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 6

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms and definitions ...................................................................................................... 7

4 Symbols .......................................................................................................................... 8

5 Principle of measurement method .................................................................................... 9

6 Apparatus ........................................................................................................................ 9

6.1 General ................................................................................................................... 9

6.2 Cryogenic system ................................................................................................... 9

6.3 Electrical measurement system ............................................................................. 10

6.4 Circuitry ................................................................................................................ 10

7 Estimation of normal state resistance (R ) and intrinsic critical current (I ) .................... 11

n ci

7.1 Calculation method ............................................................................................... 11

7.2 Geometric mean criterion for hyperbolic function fitting ......................................... 12

8 Standard uncertainty ..................................................................................................... 12

8.1 General ................................................................................................................. 12

8.2 Type A uncertainty ................................................................................................ 12

8.3 Type B uncertainty ................................................................................................ 14

8.3.1 General ......................................................................................................... 14

8.3.2 Temperature .................................................................................................. 14

8.3.3 Voltage measurement .................................................................................... 16

8.3.4 Current measurement .................................................................................... 16

8.4 Budget table ......................................................................................................... 17

8.5 Uncertainty requirement ........................................................................................ 18

9 Test report ..................................................................................................................... 18

9.1 Identification of test device ................................................................................... 18

9.2 R value ................................................................................................................ 18

9.3 I value ................................................................................................................ 18

9.4 Standard uncertainty ............................................................................................. 18

9.5 Atmospheric pressure ........................................................................................... 18

9.6 Miscellaneous optional report ............................................................................... 18

Annex A (informative) Calculation technique and practical application to high-T

Josephson junctions ............................................................................................................. 20

A.1 General ................................................................................................................. 20

A.2 Hyperbolic function fitting method ......................................................................... 20

A.3 Geometric mean method ....................................................................................... 21

A.4 Combined method ................................................................................................. 22

A.5 Estimation of R , I , u and u ....................................................................... 23

n ci A,R A,I

A.5.1 General ......................................................................................................... 23

A.5.2 High-T Josephson junction (JL350) .............................................................. 23

A.5.3 High-T Josephson junction (JL351) .............................................................. 25

A.5.4 High-T Josephson junction (TUT) ................................................................. 27

Annex B (informative) Practical application to low-T Josephson junctions ........................... 30

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SIST EN IEC 61788-22-2:2022
IEC 61788-22-2:2021 © IEC 2021 – 3 –

B.1 General ................................................................................................................. 30

B.2 Estimation of R , I , u and u ....................................................................... 30

n ci A,R A,I

B.2.1 General ......................................................................................................... 30

B.2.2 Low-T Josephson junction (IU1) ................................................................... 30

B.2.3 Low-T Josephson junction (IU2) ................................................................... 31

B.2.4 Low-T Josephson junction (IU3) ................................................................... 32

B.2.5 Low-T Josephson junction (IU4) ................................................................... 34

Bibliography .......................................................................................................................... 35

Figure 1 – Typical circuitry for voltage-current (U–I) characteristic curve measurement ........ 10

Figure 2 – Ideal U–I characteristic curve (red line) and hyperbolic function (RSJ) model

curve (dotted line) ................................................................................................................. 11

Figure 3 – Geometric mean criterion and RSJ model fitting for TUT-JJ05 at 75,8 K ............... 15

Figure 4 – Geometric mean criterion and RSJ model fitting for TUT-JJ05 at 76,3 K ............... 16

Figure A.1 – U–I curve based on resistively shunted junction (RSJ) model ........................... 21

Figure A.2 – U–I curve affected by noise-rounding and self-heating ...................................... 21

Figure A.3 – Application of geometric mean method to ideal U–I in Figure A.1 ...................... 22

Figure A.4 – Application of geometric mean method to U–I with noise-rounding and

self-heating effects in Figure A.2........................................................................................... 23

Figure A.5 – U–I curve of JL350 ........................................................................................... 24

Figure A.6 – Application of geometric mean method to Figure A.5 ........................................ 24

Figure A.7 – Result of RSJ model fitting for JL350 ................................................................ 25

Figure A.8 – U–I curve of JL351 ........................................................................................... 26

Figure A.9 – Application of geometric mean method to Figure A.8 ........................................ 26

Figure A.10 – Result of RSJ model fitting for JL351 .............................................................. 27

Figure A.11 – U–I curve of TUT with a small I .................................................................... 28

Figure A.12 – Application of geometric mean method to TUT ................................................ 28

Figure A.13 – Application of adjusted geometrical mean method to TUT ............................... 29

Figure A.14 – Result of RSJ model fitting for TUT ................................................................. 29

Figure B.1 – Application of geometric mean method to IU1 ................................................... 31

Figure B.2 – Result of RSJ model fitting for IU1 .................................................................... 31

Figure B.3 – Application of geometric mean method to IU2 ................................................... 32

Figure B.4 – Result of RSJ model fitting for IU2 .................................................................... 32

Figure B.5 – Application of geometric mean method to IU3 ................................................... 33

Figure B.6 – Result of RSJ model fitting for IU3 .................................................................... 33

Figure B.7 – Application of geometric mean method to IU4 ................................................... 34

Figure B.8 – Result of RSJ model fitting for IU4 .................................................................... 34

Table 1 – Typical relative standard Type A uncertainty for high-T Josephson junctions ....... 14

Table 2 – Budget table for R ................................................................................................ 17

Table 3 – Budget table for I ................................................................................................ 17

Table A.1 – R , I , u and u values of high-T Josephson junctions ............................. 23

n ci A,R A,I c

Table B.1 – R , I , u and u values of low-T Josephson junctions ............................... 30

n ci A,R A,I c
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SIST EN IEC 61788-22-2:2022
– 4 – IEC 61788-22-2:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SUPERCONDUCTIVITY –
Part 22-2: Normal state resistance and critical
current measurement – High-T Josephson junction
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international

co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and

in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,

Publicly Available Specifications (PAS) and Guides (hereafter referred to as "IEC Publication(s)"). Their

preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with

may participate in this preparatory work. International, governmental and non-governmental organizations liaising

with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for

Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence between

any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

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6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

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other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent

rights. IEC shall not be held responsible for identifying any or all such patent rights.

IEC 61788-22-2 has been prepared by IEC technical committee 90: Superconductivity. It is an

International Standard.
The text of this International Standard is based on the following documents:
FDIS Report on voting
90/484/FDIS 90/486/RVD

Full information on the voting for its approval can be found in the report on voting indicated in

the above table.
The language used for the development of this International Standard is English.
---------------------- Page: 10 ----------------------
SIST EN IEC 61788-22-2:2022
IEC 61788-22-2:2021 © IEC 2021 – 5 –

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in

accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available

at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are

described in greater detail at www.iec.ch/standardsdev/publications.

A list of all parts in the IEC 61788 series, published under the general title Superconductivity,

can be found on the IEC website.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under webstore.iec.ch in the data related to the

specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates that it

contains colours which are considered to be useful for the correct understanding of its

contents. Users should therefore print this document using a colour printer.
---------------------- Page: 11 ----------------------
SIST EN IEC 61788-22-2:2022
– 6 – IEC 61788-22-2:2021 © IEC 2021
INTRODUCTION

IEC 61788-22 (all parts) is a series of International Standards on superconductor electronic

devices. Superconductivity offers various possibilities of realizing sensors and detectors for a

variety of measurands. Several types of superconductor sensors and detectors have been

developed, using such features as superconducting energy gaps, sharp normal-

superconducting transition, nonlinear current-voltage characteristics, superconducting coherent

states and quantization of magnetic flux. Superconductors are influenced by interaction with

electromagnetic fields, photons, ions, etc. The superconductor sensors and detectors have

extremely high performance in resolution, time response and sensitivity, which cannot be

realized by any other sensors and detectors.

IEC 61788-22-1 lists various types of superconductor sensors and detectors. A key element of

some sensors and detectors is Josephson junction. The superconductor material types used for

Josephson junctions are divided into two categories: low-T superconductor (LTS) and high-T

c c

superconductor (HTS). This document (IEC 61788-22-2) defines a measurement method of

normal state resistance (R ) and intrinsic critical current (I ) of HTS Josephson junctions, which

n ci

are used for magnetic measurement with superconductor quantum interference device (SQUID),

detection of millimetre to terahertz band radiation and other applications.

The measurement method covered in this document is intended to give an appropriate and

agreeable technical base for those engineers working in the field of superconductor technology.

Although the mechanism of high-T superconductivity is under investigation, the occurrence of

the Josephson effect in such weak link structures as bicrystal, step-edge and ramp edge is

reliable, and characteristic parameters for conventional LTS Josephson junctions are valid also

for HTS Josephson junctions. The important parameters of HTS Josephson junctions for

designing superconductor devices are normal state resistance (R ) and critical current (I ),

n c

which are combined as I R product that is obtained experimentally. At this moment, most HTS

c n

Josephson junctions exhibit a non-hysteretic characteristic voltage-current (U–I) curve, which

is typical for superconductor/normal-conductor/superconductor (SNS) junctions. On U–I curves,

two types of distortions are often observed: noise-rounding and self-heating effects. Especially,

maximum current values without voltage drop on the U–I curves are often considerably reduced

because of the noise-rounding effect, and therefore it is difficult to estimate an intrinsic critical

current value. This document provides a method to obtain intrinsic values by selecting a data

set range to eliminate the distortions and by fitting a model function even when two effects are

present.

The critical current obtained by this standard method is therefore called intrinsic critical current

with the variable symbol of I , eliminating the noise-rounding effect on U–I curves. On the other

hand, the normal state resistance is insensitive to the noise rounding and it is possible to avoid

the self-heating effect, so that the variable symbol R is used. The I R product is more

n ci n

essential for designing superconductor devices than the I R product. I values estimated by

c n ci
this document are usually higher than experimental I values.

Practical application of this document to HTS Josephson junctions is shown in Annex A. The

estimation method in this document is applied to SNS-type LTS Josephson junctions to check

universality in Annex B.
---------------------- Page: 12 ----------------------
SIST EN IEC 61788-22-2:2022
IEC 61788-22-2:2021 © IEC 2021 – 7 –
SUPERCONDUCTIVITY –
Part 22-2: Normal state resistance and critical
current measurement – High-T Josephson junction
1 Scope

This part of IEC 61788 is applicable to high-T Josephson junctions. It specifies terms,

definitions, symbols and the measurement and estimation method for normal state resistance

(R ) and intrinsic critical current (I ), based on a combination of selecting a data set from

n ci

measured U–I curves with a geometric mean criterion and fitting a hyperbolic function to that

data set.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies.

For undated references, the latest edition of the referenced document (including any

amendments) applies.

IEC 61788-22-1, Superconductivity – Part 22-1: Superconducting electronic devices – Generic

specification for sensors and detectors

IEC 60617, Graphical symbols for diagrams: available at http://std.iec.ch/iec60617

IEC 60050-815:2015, International Electrotechnical Vocabulary – Part 815: Superconductivity:

(available at http://www.electropedia.org/
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
U–I characteristic curve
V–I characteristic curve
I–V characteristic curve

data set of voltage drop between two superconductors of a Josephson junction and current

applied to the junction
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SIST EN IEC 61788-22-2:2022
– 8 – IEC 61788-22-2:2021 © IEC 2021
3.2
normal state resistance
normal resistance

resistance between two superconductors forming a Josephson junction in a normal-conducting

state

Note 1 to entry: In a Josephson bridge junction, a normal state resistance is also defined as the resistance at a

bias current that suppresses superconductivity well above critical current, when the self-heating effect is negligible.

Note 2 to entry: In a Josephson tunnel junction, a normal state resistance is also defined as the tunnelling resistance

at a bias voltage well above 2Δ/e, where Δ is the energy gap and e is the elementary electric charge, when the self-

heating effect is negligible.
3.3
intrinsic critical current

maximum direct current that can be applied to a Josephson junction without causing a voltage

drop across the junction in the absence of noise-rounding on a U–I characteristic curve

Note 1 to entry: Critical current (I ) is the maximum direct current value that can be applied to a Josephson junction

experimentally so that it can be regarded as flowing without resistance (IEC 61788-22-1).

Note 2 to entry: The method described in this document estimates I , the value of which is usually higher than I .

ci c
3.4
geometric mean

square root of the product of dU/dI and U/I obtained from a U–I characteristic curve

3.5
noise-rounding effect
effect of noise on a U–I characteristic curve

Note 1 to entry: The U–I curve shape near I is rounded from an ideal shape by the noise-rounding effect. Because

of this, an I value is lower than the I value.
c ci
3.6
self-heating effect

effect of power dissipation due to transport current applied to a Josephson junction on a U–I

characteristic curve

Note 1 to entry: The current generates heat, and a U–I curve shape in a high current region well above I deviates

upward above a straight line corresponding to R .
4 Symbols
U voltage drop across two superconductors conn
...

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