University of Groningen. Taking topological insulators for a spin de Vries, Eric Kornelis

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1 University of Groningen Taking topological insulators for a spin de Vries, Eric Kornelis IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2017 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): de Vries, E. K. (2017). Taking topological insulators for a spin: Towards understanding of spin and charge transport in Bi2Se3 [Groningen]: Rijksuniversiteit Groningen Copyright Other 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 the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date:

2 Antonija, papa, mama en Marjon, jullie zijn de beste!

3 Zernike Institute PhD thesis series ISSN: ISBN: (hardcopy version) ISBN: (electronic version) The work described in this thesis has been performed in the research group Spintronics of Functional Materials, which is part of the Zernike Institute for Advanced Materials at the University of Groningen, the Netherlands. The research has been supported by the Bonus Incentive Scheme (Dieptestrategie) of the Dutch Ministry for Education, Culture, and Science (OCW). Cover: The cover displays the abstract representation of highway traffic at night where headlights and taillights are the unique feature that describes the direction of movement. In the context of this thesis, the headlights and taillights represent the two distinct spin states of charge carriers. Like the lights in traffic, the spin states in topological insulators immediately relate to the charge carrier s momentum. As the endpoint of the highway is in the dark, so is the one of topological insulators. This thesis contributes to the understanding, but it remains an effort to employ the full potential of topological insulators. The image and its rights were purchased from Shutterstock. Idea by: Eric de Vries. Suggestions were made by Antonija Marjanovic and Jermaine de Beauvesier Watson for which the author is very thankful. Printed by: Gildeprint, Enschede

4 Taking topological insulators for a spin Towards understanding of spin and charge transport in Bi 2 Se 3 Proefschrift ter verkrijging van de graad van doctor aan de Rijksuniversiteit Groningen op gezag van de rector magnificus prof. dr. E. Sterken en volgens besluit van het College voor Promoties. De openbare verdediging zal plaatsvinden op vrijdag 24 november 2017 om uur door Eric Kornelis de Vries geboren op 26 maart 1990 te Delfzijl

5 Promotores Prof. dr. T. Banerjee Prof. dr. ir. B.J. van Wees Beoordelingscommissie Prof. dr. ir. B.J. Kooi Prof. dr. M.S. Golden Prof. dr. S.O. Valenzuela

6 Contents Summary Samenvatting V VII 1 Introduction Topology: Exploring new states of matter Topological insulators and their high potential Thesis outline References 6 2 Properties of topological insulators Crystal structure Topological band theory Bi-based topological insulators Growth Thin films Bulk crystals, nanoplatelets, and nanoribbons References 20 3 Studying charge transport at metal/topological insulator interfaces Introduction Measurement schemes to study transport at the interface Ballistic-electron emission microscopy Hot-electron transistor Three-terminal measurements Device fabrication BEEM devices Solid-state device geometries Results and Discussion BEEM devices Solid-state device geometries Conclusions References 46 I

7 4 Investigation of helicity-dependent photocurrent generation in Bi 2 Se Introduction Theory Generation of current through optical excitation Transient charge-carrier dynamics in topological insulators Experimental Methods Results and Discussion Temperature dependence Position dependence Conclusions References 68 5 Charge transport under high magnetic fields in Bi 2 Se Introduction Lifshitz Kosevich theory Results and Discussion Conclusions Appendix Additional data Derivation of the two-carrier model Details on analysis of oscillations Improvement of the FFT spectra Negative magnetoresistance Weak antilocalization References Investigating charge-current-induced spin voltage signals in Bi 2 Se Introduction Theory Detection of charge-current-induced spin accumulation in topological insulators Estimation of the charge-current-induced spin polarization Results and Discussion Conclusions Outlook Appendix Additional Measurements Modeling of current spread Analytical expression for fringe fields References Taking topological insulators for their spin: A feasibility study Production of topological insulator materials Mining and purification of raw materials Environmental impact Large-area growth 134 II

8 7.1.4 Conclusions Applicability of topological insulators Spintronic applications Thermoelectric applications Applications for optics Conclusions References 143 Appendix: Details on fabrication 147 Acknowledgments 151 III

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