Damascelli, Andrea

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   University of GroningenOptical spectroscopy of quantum spin systemsDamascelli, AndreaIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1999Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Damascelli, A. (1999). Optical spectroscopy of quantum spin systems. s.n.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 20-06-2022AcknowledgementsMeeting Dick van der Marel was just a coincidence. At that time I was working in the eldof nonlinear optics and I had never heard of him. Then again, he had never heard of meeither! Now, after the four years that I spent working with him, I can indeed say that thiscoincidence was a very lucky one. I really appreciate his way of both doing research andguiding the students in their projects. As an experimental physicist, his aim is not only toobtain relevant `experimental facts', but also to understand them on a deep theoretical andintellectual level. As a supervisor, he is constantly inspiring and confronting his students,but, at the same time, he grants them all the freedom they wish. In other words, thanksDick for what I learned from you, for your contagious enthusiasm, and for the great timewe had together. I hope that these four years will be the basis of a long friendship andfruitful future collaborations.Working in Groningen has been a special experience also because of the high levelscientic environment. I had the opportunity to interact with scientists who have vastknowledge and experience, like George Sawatzky, Daniel Khomskii, and Thom Palstra. Iwould like to thank George Sawatzky for the interest he always showed in my work and, inparticular, for the series of evening lectures he gave for Ph.D. students. It was extremelyuseful and pleasant being there: I never saw anybody else able to talk about solid statephysics in such a fascinating way. I am very grateful to Daniel Khomskii for the carefulreading of my manuscript but, above all, for the `daily discussions' we had, which wereextremely important for me when entering the realm of low dimensional spin systems. He isindeed a theoretician who knows how to talk to experimentalists. I am particularly gratefulto Thom Palstra for the intense collaboration we had on the project of 0-NaV2O5. Hisalternative experimental approach and the occasional `divergence of opinions' have beenextremely precious and stimulating.Obviously, not only the `big shots' made Groningen such a pleasant place for me. Thenumber of people is much larger and, among them, I would like to thank, rst of all, CorBos, the godfather of our `Cor-related experimental systems'. His technical and much morethan technical assistance was irreplaceable. Secondly, I would like to express my gratitudeto Auke Meetsma and Jan de Boer, who tried hard to turn me into a crystallographer;Henk Bron, who polished and `smoked' most of my samples; and Frans van der Horst, whowas never tired of having to enlarge my quota on our work-station.Special thanks to Maxim Mostovoy, a brilliant theoretician and an even more brilliant(and patient) teacher. I really enjoyed our frequent discussions.133134 AcknowledgementsAnd now, the people of my group, who I could write a book about. Markus Gruninger,the German paranimf : We shared everything, life inside and outside the lab, the experienceof having a son (I mean, you had yours and I had mine!)...not to mention our toughdiscussions (the one we had at the bottom of the Grand Canyon was great!). ThanksMarkus, I'm sure our friendship will not be just a four year experience. Johan Feenstra:thanks Johan, you also are a tremendous friend, even though we did not really shareeverything: I'm sorry, but I was not brave enough to eat a kroket together with you.However, I was very pleased to see how much you did appreciate my risotto and, remember,you will always be welcome. Anna-Maria Janner: What can I say? We already told eachother everything, and in Italian! One remark: Life has indeed changed in our oce sinceyou left - it's just so quiet! Thanks Anna-Maria, and when Johan comes to our place for arisotto, don't be shy and join him! Karina Schulte: I really enjoyed working with you whenyou were my student and later when you became my k-space teacher. Most important ofall, we had a great time: You, me and the Bomem. Dank je, Karina, for the translation ofthe Samenvatting, along with all the `Dutch mail' that, strangely enough, I was receivingevery day. One last thing, toti toti ! Let me now continue by thanking people in a moreconcise way: Jeroen van der Eb (see you in Stanford?), Diana Dulic (see you and Walter inSardinia?), Artem Tsvetkov (spasibo, tovaristch : We had a short but good time together),Cristian Presura (who is taking good care of my samples), Hajo Molegraaf (who took careof the layout of the front cover), Ronald Hesper (and his brilliant car), Mark James (whotook care of considerably improving the English here and there), Jae H. Kim and JurgenSchutzmann (my personal FTIR trainers, together with Clay Paays from Bomem), andthe `Italian Maa': Salvatore Altieri and Alberto Morpurgo (se vedemo, testine di silicio).Although he doesn't belong to the Solid State Physics Lab of the University of Groningen,I would also like to thank Fabio Fiorani, the Italian paranimf : thanks Fabio, for beingsuch a great contrappeso for so many years!During my Ph.D research I had the opportunity to interact with many people outsidethe University of Groningen. First of all, a big thank you goes to the people who grew thebeautiful and large single crystals used in this experimental investigation: A.A. Menovskyfor the transition-metal mono-silicide samples, and J. Jegoudez, G. Dhalenne, and A.Revcolevschi for the CuGeO3 and 0-NaV2O5 samples.I am indebted to M. Fath, J. Aarts, and J.A. Mydosh for their intense cooperation onthe FeSi project (with a continuous exchange of `unpublished' data), and to V.Vescoli andL.Degiorgi for numerous discussions and for providing me with their optical data on RuSi.I also enjoyed fruitful discussions with P.H.M. van Loosdrecht, D. Smirnov, J. Leotin, B.Buchner, T. Mizokawa, J.E. Lorenzo, P. Lemmens, G.S. Uhrig, and M. Braden.I would like to take this opportunity to acknowledge M.J. Rice and G. Aeppli for theircareful reading of this manuscript, and for their constructive remarks. Furthermore, Iwould like to express my gratitude to M.J. Rice for the several `private communications'on theoretical aspects of this research project.The last thank you goes to Fulvio Parmigiani, who supervised my undergraduate thesisproject and suggested to me to come to Groningen for my Ph.D. research. Since then, hehas never stopped giving me good advice, and unlimited scientic and moral support.135At this point some people may wonder:Isn't this guy going to thank all those friends not scientically involved in his thesis work ?And what about his parents, who made everything possible in the rst place ??And, even more surprisingly, isn't he going to thank his beloved wife Barbara, who let himgo to The Netherlands for his Ph.D. after only two weeks of marriage, who one year latermanaged to nd an occupation in Groningen and moved over there so that they could livetogether, who gave birth to their son Matteo, who was waiting for him to come home fromthe lab all those nights and weekends, who always encouraged him, and who even acceptedto be put on the front cover of his thesis ???Don't worry, I will do that, but in real life !!!List of Publications A. Damascelli, G. Gabetta, A. Lumachi, L. Fini, and F. Parmigiani.Multiphoton Electron Emission from Cu and W: an Angle-Resolved Study.Physical Review B 54, 6031 (1996). A. Damascelli, K. Schulte, D. van der Marel, M. Fath, and A.A. Menovsky.Optical Phonons in the Reectivity Spectrum of FeSi.Physica B 230-232, 787 (1997). A. Damascelli, K. Schulte, D. van der Marel, and A.A. Menovsky.Infrared Spectroscopic Study of Phonons Coupled to Charge Excitations in FeSi.Physical Review B (Rapid Communications) 55, R4863 (1997). A. Damascelli, D. van der Marel, F. Parmigiani, G. Dhalenne, and A. Revcolevschi.Infrared Signatures of the Spin-Peierls Transition in CuGeO3.Physical Review B (Rapid Communications) 56, R11 373 (1997). A. Damascelli, D. van der Marel, F. Parmigiani, G. Dhalenne, and A. Revcolevschi.Infrared Reectivity of Pure and Doped CuGeO3.Physica B 244, 114 (1998). D. van der Marel, A. Damascelli, K. Schulte, and A.A. Menovsky.Spin, Charge and Bonding in Transition Metal Mono-Silicides.Physica B 244, 138 (1998). A. Damascelli, D. van der Marel, M. Gruninger, C. Presura, T.T.M. Palstra,J. Jegoudez, and A. Revcolevschi.Direct Two-Magnon Optical Absorption in 0-NaV2O5: \Charged" Magnons.Physical Review Letters 81, 918 (1998). A.A. Tsvetkov, D. van der Marel, K.A. Moler, J.R. Kirtley, J.L. de Boer, A. Meetsma,Z.F. Ren, N. Koleshnikov, D. Dulic, A. Damascelli, M. Gruninger, J. Schutzmann,J.W. van der Eb, H.S. Somal, and J.H. Wang.Global and Local Measures of the Intrinsic Josephson Coupling in Tl2Ba2CuO6 as aTest of the Interlayer Tunneling Model.Nature 395, 360 (1998).137138 List of Publications A. Meetsma, J.L. de Boer, A. Damascelli, J. Jegoudez, A. Revcolevschi,and T.T.M. Palstra.Inversion Symmetry in the Spin-Peierls Compound 0-NaV2O5.Acta Crystallographica C 54, 1558 (1998). A. Damascelli, D. van der Marel, J. Jegoudez, G. Dhalenne, and A. Revcolevschi.The Symmetry Problem in 0-NaV2O5.Physica B, in press (1999). M. Gruninger, D. van der Marel, A. Damascelli, A. Zibold, H.P. Geserich, A. Erb,M. Klaser, Th. Wolf, T. Nunner, and T. Kopp.Charged Magnons and Magneto-Elastic Polarons in the MIR Spectrum of YBa2Cu3O6.Physica C, in press (1999). A.A. Tsvetkov, D. Dulic, D. van der Marel, A. Damascelli, G.A. Kaljushnaia, J.I.Gorina, N.N. Senturina, B. Willemsen, N.N. Kolesnikov, Z.F. Ren, J.H. Wang, A.A.Menovsky, and T.T.M. Palstra.Systematics of c-axis Phonons in the Tl and Bi Based Cuprate Superconductors .Submitted to Physical Review B (1999).Happy EndDuring the four years I spent in Groningen working on my Ph.D., I tried many and manytimes to explain to people, not belonging to the `Physics Flying Circus', what my work wasall about. In particular, we usually went through a rather reproducible series of questionsand answers (to be completely honest, I was often questioning myself in a similar way).Below, I would like to go through these questions once more:What are you working on?Once this question has been formulated, I take a deep breath, I see all my life passingbefore my eyes like in a movie, and then I start talking. In the simplest possible way.After a little while we all feel we are dealing with a major communication problem here.With hindsight, my interrogators realize this was not such a clever question, in the rstplace. After all, what I am exactly doing is not so important to them. The essential point is:Is it useful?With this question people usually mean whether the things I am doing, independentlyof how am I doing them, will eventually result in any practical application that could im-prove the quality of life. Unfortunately, I have to answer that I do not think so. Not evenin the very far future. But I do not miss the opportunity to stress how interesting theseexperimental studies are from the point of view of `fundamental research'. However, thedisappointment at this point is usually so deep that people reply:That's what we are paying you for?!You can imagine that this could easily be the end of our conversation and, probably, of myjob: People could completely disagree with the use the government is making of their taxcontributions and decide not to nance academic activities any longer. Fortunately, thisis usually not the case, at least not in The Netherlands. About Italy, I am not that sure.139Stellingenbehorende bij het proefschriftOptical Spectroscopy of Quantum Spin Systemsvan Andrea Damascelli1. In the transition-metal mono-silicides vibrational degrees of freedom are coupled tolow-energy electron-hole excitations: \Charged Phonons".Chapter 2 of this thesis2. Spin-ip excitations can carry a nite electric dipole moment: \Charged Magnons".Chapter 4 and 5 of this thesis3. In reectivity spectra an optical phonon does not always have to look like a peak.4. The nonexistence of phonon softening at TSP in CuGeO3 is an experimental fact.M. Braden et al., Phys. Rev. Lett. 80, 3634 (1998)5. The expression `this is an experimental fact' means a lot of work for theoreticians.6. Fluid dynamics can be successfully applied to the study of plant organ growth.7. Leonardo da Vinci said: `It is not enough to believe what you see, you must alsounderstand what you see'. For completeness, I would personally like to add: `...Butyou will never understand what you see, if you do not believe it rst'.8.  o ~  ~: To act implies suering.~ o&: Suering leads to knowledge.Aeschylus9. The water cycle is well known to everybody: Water falls on the earth in form ofrain, snow or hail. It collects in streams, lakes and rivers, nally reaching the ocean.This water then evaporates forming clouds and, eventually, falls again and the cyclerepeats. What is not known to the majority of the people is that `most' of this waterfalls on The Netherlands.10. The tradition of Sinterklaas is wonderful for kids. But what an exhausting job forthe Zwarte Pieten !

Optical spectroscopy of quantum spin systems

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Optical spectroscopy of quantum spin systems

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