«A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Physics in the GRADUATE DIVISION of ...»
Exploring Competing Orders in the High-Tc Cuprate Phase Diagram Using
Angle Resolved Photoemission Spectroscopy
Daniel Robert Garcia
A dissertation submitted in partial satisfaction
of the requirements for the degree of
Doctor of Philosophy
UNIVERSITY OF CALIFORNIA, BERKELEY
Committee in charge:
Professor Alessandra Lanzara, Chair Professor Dung-Hai Lee Professor Yuri Suzuki Fall 2010 Exploring Competing Orders in the High-Tc Cuprate Phase Diagram Using Angle Resolved Photoemission Spectroscopy Copyright c 2010 by Daniel Robert Garcia Abstract Exploring Competing Orders in the High-Tc Cuprate Phase Diagram Using Angle Resolved Photoemission Spectroscopy by Daniel Robert Garcia Doctor of Philosophy in Physics University of California, Berkeley Professor Alessandra Lanzara, Chair With more than a quarter century of study, the high temperature superconducting cuprates still represent one of the most active areas of research in condensed matter physics.
Its complex phase diagram continues to present challenges to our understanding, stemming from its correlated electronic nature. Being able to tease out the eﬀect of diﬀerent lattice orderings and their eﬀects on electronic states may be crucial to understanding the physics of the cuprates where such orderings may be crucial to the phase diagram. Thus, because of its ability to directly probe electronic band structure, Angle Resolved Photoemission Spec- troscopy (ARPES) is an ideal probe to study the eﬀects of competing orders on electronic states near EF.
This thesis will be organized in the following way. Chapter 1 provides a broad intro- duction to the physics central to our work including concepts of band structure and Fermi liquid theory, as well as more exotic phenomena explored throughout the thesis. Chapter 2 introduces the ARPES technique, how it is physically understood via concepts like Green’s functions, and traditional methods of data analysis. Chapter 3 explores magnetic ordering and its eﬀect on both core level and valance band states in the iron oxypnictides. From the near-EF electronic states, we ﬁnd that the magnetic physics of the parent compound may still be present even at superconducting dopings. Chapter 4 explores charge density wave (CDW) ordering by looking at the rare earth ditellurides. This ARPES work establishes LaTe2 as the ﬁrst quasi-2D CDW system to behave like a true Peierls transition, with both Fermi surface nesting tied to a metal - to - insulating transition. Chapter 5 explores the effect of lattice strain on electronic states by studying the single layered Bi2201 cuprates with lanthanide substitution. The eﬀect of this substitution competes with superconductivity and appears to enhance bosonic modes acting on the nodal point states which are otherwise unaﬀected. Chapter 6 takes the speciﬁc case of Nd-Bi2201 and ﬁnds evidence of a distinct crossover point in the electronic states near EF segregating the nodal point states. Finally, Chapter 7 provides a summary of our work and its conclusions.
When undertaking a doctoral journey, there are so many people who deserve thanks and recognition for the manifold ways they have made this entire enterprise possible.
First, and foremost, I wish to thank my advisor, Prof. Alessandra Lanzara, who has made this journey possible for me. I thank you for your guidance, wisdom, and faithful support of this work and my studies as well as the generous number of conferences, talks, and experiments you have enabled me to attend. The complicated relationship between a student and their advisor can never be adequately summarized in so few words as these. But I am, in all senses, deﬁned by my experience as your student, and whether the waters we sailed were turbulent or placid, I thank God to have been in your research group.
I wish to thank Prof. Gey-Hong Gweon who, perhaps more than anyone else, taught me what Angle Resolved Photoemission is all about when I was just beginning. His intelligence, experience, and attention to detail gave me a model of what a physics experimentalist could be. I thank you for your patience with me, your training on equipment and sample preparation, and for your scientiﬁc guidance particularly towards my work on the Ditellurides.
Our group has been enriched by numerous postdocs and visiting scientists, all of whom I wish to thank. For Prof. Andreas Bill, thank you for simply being so giving of your time to a ﬁrst year physics grad student who didn’t know a mean ﬁeld theory from a hole in the ground.
Your patience and perspective of the parallel world of a physics theorist not only encouraged me during that diﬃcult ﬁrst year, but I believe your presence was good for our entire group.
For Prof. Kyle McElroy, thank you for your physics insights, personal discussions, and the breadth of your knowledge as well as numerous times on the beamline taking data with me.
For Marco Papagno, thank you for your kindness and the numerous experiments that you participated with. For Choonkyu Hwang, beyond the obvious assistance with data taking and all-nighters, as well as assisting the work which became part of both the pnictide and crossover papers, thank you for numerous times of just talking about the physics and where our work and careers were going. It has always been a pleasure.
I owe a debt of gratitude to the older graduate students of our group. Each one of them has “shown me the ropes” of the Lanzara Group and their immediate mentorship has made this journey possible on a regular basis. All of them have endured many long nights on the beamlines, teaching me the self-sacriﬁcial nature of our group, that we all help each other’s projects when we can. All of them taught me the nuances of the beamlines and in house equipment, without which none of this would be possible. For Chris Jozwiak, your eventemper, your experimental brilliance, your patience, and, in the later years, your leadership, have made my time here all the better and richer. For Shuyun Zhou, you were always a bright star in our group, and well deserved. Your eﬀort and energy admittedly set the bar quite high for us. You, particularly, were important to my beginnings in the group, introducing me to the IGOR analysis package, and the analysis techniques I needed to know to proceed.
And for Jeﬀ Graf, as I transitioned into the cuprates, your assistance, knowledge, comedy, procedures, perspective, all of it made what appeared a frustrating project, surmountable and even achievable.
iii For David Siegel, we were always peers, and it is a signiﬁcant gift to progress through one’s time as a doctoral student with another. Thank you not only for the beamtimes, the discussions, the humor, and all the other ways in which you have helped make this dissertation possible. But thank you for the times in the courtyard talking, venting, and reﬂecting.
For the “younger” students, many thanks to Chris Smallwood, Sebastian Lounis, Xiaozhu Yu, Michelle Yong, and Annemarie Kohl, for all the times on beamlines, the discussions, and the life each of you have brought to our group. When times were diﬃcult, I could always lean on the fact that I enjoyed the dynamic and the personalities of our group.
I want to thank the technical staﬀ and the beamlines from which all the data of this thesis comes from. First, at the Advanced Light Source, the team at BL 7 of Eli Rotenberg, and in particular Jessica McChesney, for their assistance in the work on the ditellurides.
For the teams at BL 10 who we call up, late into the night at times, particularly Norman Manella, Sung-Kwon Mo, and David Kilcoyne. Finally, at BL 12, Alexei Fedorov who has been so important to our group over the years and for me particularly with our work on the pnictides.
At the Stanford Synchrotron Light Source, where the vast majority of the cuprate work presented here came from, I want to thank the team at BL 5-4 especially Dunghui Lu and Rob Moore. I’ve always enjoyed working with both of you and it made the entire, sometimes soul crushing, experience of late nights in that windowless facility a little more bearable.
Thank you for all your support and training.
The best experiments without theoretical support are like a ship with no charts. And so I wish to thank the groups who have, in one way or another provided those charts. For Prof.
Dung-Hai Lee, thank you for your guidance for our entire group and for your participation on my qualifying exam committee. For Prof. Antonio Castro-Neto, thank you for your insights during the early times with tellurides. And thank you to Prof. Philip Phillips and his group for their valuable theoretical support when it came to the pnictide work.
I would like to also thank Feng Wang for his participation on my qualifying exam committee and similarly for Yuri Suzuki who might be one of the only other people to have actually read this thesis.
And of course, without samples, we would have very little to do. So I want to thank our sample growing colleagues from the Birgeneau and Bourret-Courchesne Groups for our pnictide samples. I also want to thank our Korean colleagues M.H. Jung and Y.S. Kwon for the telluride samples. Finally, I want to thank H. Eisaki for supplying so many of our group’s samples and my strained cuprate samples in particular.
All of these colleagues have made this work possible. But anyone who has gone through such a program knows that it is more than just your colleagues which make all of this possible. And for me, this has been particularly true as I wish to acknowledge now.
I have been undeservedly blessed to have communities of both undergraduates and graduate students with me on the journey. To begin, I want to acknowledge the Veritas Fellowship iv and the work of Carrie Bare in helping to create, with staying power, a community of graduate and professional students who deeply believe that the life of the mind and the Christian walk are essential partners. In particular, I want to thank all of the members and alumni of the Tuesday Men’s Group, too many for me write (though I wish I could!), who week in and week out, come together to share life and food and prayer and insights and laugher and grief together over these years. From this group I wish to acknowledge Onsi Fakhouri, my dear friend who has been with me since the day we both arrived at the end of the summer 2004 to start our doctoral programs. To have an apartment mate whom you get along with is a great blessing. But to have one, who is so perfectly suited to the journeys that both of us have been on as doctoral students, is grace upon grace.
I also want to acknowledge the Physics Prayer group and all the members (both physics and non-physics) who have sat there on the grass, in the shadow of the Campanile, venting and hoping as we made our way slowly through our doctoral studies. From this group I wish to acknowledge Xiaosheng Huang whose experience, wisdom, perspective, candor, and presence continued to bless me in diﬀerent ways during the diﬀerent seasons of my graduate work.
If am truly honest with myself and ask, “Why do you think you ended up at Berkeley?” I cannot help but suspect that the Ph.D was simply a means for me to be among the students particularly (but not exclusively) of the Intervarsity Christian Fellowship. If my grad community gave me wisdom and guidance, the undergraduates gave me hope and purpose when nothing in my research was working. I wish to acknowledge the campus staﬀ of this group, in particular Erina, Carol, Casey, Nikki, Ryan, Wendy, Jen, Javier, and Collin.
I wish I could list and name every one of the students over the last six years I have had the privilege to talk to and be with as they shared life and faith and struggles with me. A special thank you Class of ’05 for helping me ﬁnd a welcoming community (all the more impressive since you were all seniors) and a place to be on Monday nights that kept me going that ﬁrst crazy year. For the Class of ’06 for all the laughs and all the good times at Manhouse when my research was beginning to sap away my soul. For the Class of ’07 for the privilege of teaching you and you teaching me, in that wonderful year before my research made it increasingly impossible. For the Class of ’08 for watching you grow up from freshman to seniors and giving me hope that the world is still in good hands. For the Class of ’09, you will always be both young yet wise to me, and hanging out with you at the College apartments, doing my data analysis, fun times always. For the Class of ’10 for still embracing an old timer like me and again proving what I’ve always known: that life is more than the work we do.
To all the students, current and alumni, Intervarsity or otherwise, my thanks to you for sharing life together and showing me that when I was most down, most demoralized, and most without purpose, you allowed me feel brilliant again, purpose again, useful again.
There is more that I have learned than you realize. Even if all my papers, research, and studies be for naught, you have given me ample purpose to my time here. Thank you.
I want to thank my friends at First Presbyterian Church of Berkeley, particularly the v pastoral staﬀ for your wisdom and guidance, in particular Joshua McPaul. If I have gained wisdom, First Pres has been important in that journey. And in writing that, I can’t help but thank the Stephen Ministry community and the work of Carol Johnston. It has been a privilege to serve with you.
Of course, there is the journey to even come to Berkeley and so I wish to thank all of the MIT faculty, friends, and communities who supported me, encouraged me, taught me, and trained me that I could even get to this point. I particularly wish to thank my undergraduate thesis adviser, Prof. Young Lee, whose guidance during my senior year was incredibly gracious and valuable. I also want to thank Prof. Eric Hudson who not only was a good mentor, but continues to be a great mentor and excellent teacher and physicist.
And quite possibly none of this would have come to pass if not for Jim Hicks. So much of how I teach science or work with students, has its origins in your example. It’s been more than 10 years since I curiously wandered into your AP Physics class. Thank you.