Effect of Magnetic Field on the Thermal Conductivity of Single Crystal

ABSTRACT

This research investigated the effect of magnetic field on the thermal conductivity of high temperature type II superconductors. The result suggested that the thermal conductivity of high temperature type II superconductor YBa2Cu3O7- decreases as the applied magnetic field increases at a given temperature. We also found out that the superconducting energy gap of YBa2Cu3O7- decreases in response to increasing temperature and applied magnetic field. At a critical temperature of about 100K, we noted a sharp decrease in the energy gap of the substance. This implies that, the superconducting energy gap decreases in response to increase in temperature until at a critical temperature of about 100K,the material transits to normal state, thus resulting to increase in superconducting energy gap again. Our finding also revealed that specific heat of YBa2Cu3O7- is proportional to electron density.

TABLE OF CONTENTS

Title Page i

Certification ii

Dedication iii

Acknowledgement iv

Abstract v

Table of contents vi

List of Tables viii

List figure ix

1. General Introduction 1

1.1 Introduction and Discovery of Superconductivity 1

1.2 Structure of single crystal of YBa2Cu3O7- 3

1.3 Basic properties of Superconductors 5

1.3.1 Electromagnetic properties 6

1.3.2 Thermal properties 9

1.3.3 Isotope effect 11

1.3.4 Tunneling 11

1.4 Type-I and Type-II 12

1.5 Applications of High-Tc Superconductors 13

1.5.1 High magnetic field, High direct current 13

1.5.2 Alternating current devices 13

1.5.3 Bolometer 14

1.5.4 Josephson tunneling 14

1.5.5 Medicine 15

1.6 Theoretical Basis of Superconductivity 15

1.6.1 Phenomenological theories 15

1.6.2 The Ginzburg-Landau theory 16

1.6.3 Microscopic Theory 16

1.7 Purpose of the study 17

2 .0 Review of Literature 18

2.1Superconductivity in YBa2Cu3O7- 18

2.2 Thermal Conductivity of High-Tc Superconductors 19

2.3 Magneto-thermal conductivity of high-Tc superconductors 21

3.0 Magneto- thermal conductivity of high-Tc type II superconductors (single crystal of YBa2Cu3O7-) 26

3.1 Introduction 26

3.1.1London Equation 26

3.2 Magneto-Temperature Dependence of Superconducting Energy Gap of YBa2Cu3O7- 28

3.3 Calculation of Thermal Conductivity of YBa2Cu3O7- 29

3.4 Superconducting Energy Gap 31

3.5 Critical Temperature 34

3.6 Specific Heat of YBa2Cu3O7- 35

4. 0 Discussions and Conclusion 38

4.1 Discussion 38

4.2 Conclusion 39

References 40

Appendix A: Program for Calculating Thermal Conductivity of YBa2Cu3O7- 44

Appendix B: Program for Calculating Superconducting Energy Gap of YBa2Cu3O7- 45

Appendix C: Program for Calculating Specific Heat of YBa2Cu3O7- 46