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The London School of Economics and Political Science The London School of Economics and Political Science Modelling High Superconductivity: A Philosophical In Experiment a Maria Elena Di Bucchianico A thesis submitted to the Department of Philosophy, Logic and Scientific Method of the London School of Economics for the degree of Doctor of Philosophy, London, September 2009 UMI Number: U615704 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. Dissertation Publishing UMI U615704 Published by ProQuest LLC 2014. Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 -rUr cr .c f ^IC7 Library &*shLto^yDfPo,|llcal an*eara"K*"K» I2-IS6H Declaration I certify that the thesis I have presented for examination for the PhD degree of the London School of Economics and Political Science is solely my own work other than where I have clearly indicated that it is the work of others (in which case the extent of any work carried out jointly by me and any other person is clearly identified in it). The copyright of this thesis rests with the author. Quotation from it is permitted, provided that full acknowledgement is made. This thesis may not be reproduced without the prior written consent of the author. I warrant that this authorization does not, to the best of my belief, infringe the rights of any third party. 2 Abstract This thesis tells the story of the Balkanization of the theory community in High Temperature Superconductivity (HTS) and of the many roles experimental evidence has been playing in the battles there. In the twenty-five years that followed the discovery of HTS, the Condensed Matter Physics (CMP) community has experienced extreme difficulty in trying to reach a consensus on a ‘final’ theory. I will explore some of the reasons for such dissent, starting from testimonies that I collected through personal interviews with HTS physicists. I will focus on the way experiments actively contribute to the formulation of theories. I claim that there is a tension between the different methods and aims of two scientific traditions as they implement the contribution from experiments. This tension will be illustrated through the discussion of several episodes from the history of Superconductivity and CMP research. In particular the paradigmatic quarrels between two of the major players in the history of superconductivity, physicists PW Anderson and B Matthias, will be presented to explore the meeting of theoretical and experimental driving forces and their impact on the evaluation of theories and research programmes. I will also argue that the ambiguity in the theories of evidence employed by the warring camps in HTS allows each of them to claim empirical adequacy for itself and deny it to the opponents, and I shall raise questions about whether the standards of evidence employed there are consistently applied and grounded. 3 4 Table of Contents CHAPTER ONE - INTRODUCTION....................................................................................7 CHAPTER TWO................................................................................................................. 14 2.1 Inspecting Experimental Practice ...............................................................................15 2.2 The Challenge to the Standard View on the Theory-Experiment Relation ........... 16 2.3 Theory Independence of Observations and Conceptualization ..............................18 2.4 The Many Roles of Experiment ...................................................................................19 2.5 Phenomena and Models ..............................................................................................22 2.6 Phenomenological Models..........................................................................................25 2.7 Exploratory Experiment ..............................................................................................29 2.8 The Empiricist and Principled Traditions .................................................................34 CHAPTER THREE..............................................................................................................38 3.1 Door Meten tot Weten - From Measurement to Knowledge ..................................39 3.2 From Measurement to Superconductivity ................................................................ 44 3.3 The Traditions on Traditional Metals ........................................................................48 3.4 The Empiricist Tradition again: Superconductivity and Ferromagnetism ........... 54 3.5 Misleading Experiments and Sturdy Theories ..........................................................60 3.6 The Meissner Effect and London's Conceptual Revolution .....................................66 CHAPTER FOUR................................................................................................................73 4.1 From London to USSR and USA .................................................................................. 74 4.2 Bardeen and Traditions ...............................................................................................78 4.3 BCS................................................................................................................................. 81 4.4 On Feynman - Don't Ask What the Theory Can Do for You. Ask What You Can Do for the Theory .............................................................................................................. 89 4.5 Methodology Meets Scientific Success - Feynman and Bardeen ........................... 93 CHAPTER FIVE..................................................................................................................98 5.1 Posing the Challenge - Bernd Matthias ...................................................................99 5 5.2 Don't Ask What the Theory Can Do for You. Ask What You Can Do for the Theory - Revisited...................................................................................................................104 5.3 Traditions in Discussion ........................................................................................... 110 5.4 Can the Theory Do What We Ask of It, Anyway? - the Limit for Tc and the Discovery of HTS ........................................................................................................116 5.5 The Central Dogmas.................................................................................................. 119 CHAPTER SIX.................................................................................................................. 124 6.1 Why Is Hotter Different? ........................................................................................... 124 6.2 Why is Hotter a Problem for Theory? ......................................................................129 6.3 Theories of HTS .......................................................................................................... 131 6.4 Dissent is Hotter .........................................................................................................137 6.5 Setting the Standards with Experiments .................................................................140 6.6 Traditions and HTS ....................................................................................................143 CHAPTER SEVEN............................................................................................................155 7.1 Experiments and Theories of Evidence in HTS ......................................................156 7.2 Underdetermination and the Contribution of ARPES ........................................... 161 7.3 The Kink and the Toothbrush Theories of HTS ......................................................167 7.4 Epilogue.......................................................................................................................177 APPENDIX - Sample Interview ...................................................................................179 Bibliography ................................................................................................195 6 CHAPTER ONE - INTRODUCTION This thesis tells the story of the Balkanization of the theory community in High Temperature Superconductivity (HTS) and of the many roles experimental evidence plays in the battles there. Superconductivity is a peculiar phenomenon observed in certain materials when they are cooled to below a temperature characteristic of that material, known as the superconducting transition temperature (Tc). Superconductors are characterized by the complete absence of electrical resistance and the ability to expel external magnetic fields. Conventional or Low Temperature Superconductors (LTS) were first observed a century ago and later explained through the Bardeen-Cooper-Schrieffer (BCS) theory. BCS theory was formulated in the 1950s and won its proponents the Nobel Prize in 1972, becoming not only the leading theory in Condensed Matter Physics but also one of the most compelling successes of theoretical physics. BCS derived a formula for the temperature at which a superconducting
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