Cover Page
The handle http://hdl.handle.net/1887/68031 holds various files of this Leiden University
dissertation.
Author: Lahabi, K.
SPIN-TRIPLET SUPERCURRENTS
OF ODD AND EVEN PARITY
IN NANOSTRUCTURED DEVICES
Proefschrift
ter verkrijging van
de graad van Doctor aan de Universiteit Leiden,
op gezag van Rector Magnificus prof.mr. C.J.J.M. Stolker,
volgens besluit van het College voor Promoties
te verdedigen op dinsdag 4 december 2018
klokke 11.15 uur
door
Promoter:
Prof. dr. J. Aarts Universiteit Leiden Promotiecommissie:
Prof. dr. ir. A. Brinkman Universiteit Twente
Prof. dr. M. Eschrig Royal Holloway, University of London Prof. dr. Y. Maeno Kyoto University
Prof. dr. E. R. Eliel Universiteit Leiden Prof. dr. ir. T. H. Oosterkamp Universiteit Leiden
Casimir PhD series, Delft-Leiden 2018-45 ISBN 978-90-8593-375-5
An electronic version of this thesis can be found at
https://openaccess.leidenuniv.nl/.
Cover design: Kaveh Lahabi Copyright © 2018 Kaveh Lahabi
C
ONTENTS
1 Introduction 3
References. . . 9
2 Pairing symmetry 11 2.1 General symmetry classes. . . 11
2.2 Pairing symmetry of Sr2RuO4. . . 15
2.2.1 Sr2RuO4: basic properties . . . 15
2.2.2 d -vector formalism . . . 17
2.2.3 Possible symmetries for Sr2RuO4. . . 20
References. . . 25
3 Spin-triplet Cooper pairs in magnetic hybrids 29 3.1 Proximity Effect . . . 29
3.1.1 Spin-active interfaces . . . 31
3.1.2 Long-range triplet correlations. . . 33
3.1.3 Josephson effect . . . 35
3.1.4 Long-range triplet supercurrents. . . 37
3.2 Micromagnetic Simulations. . . 41
3.2.1 Micromagnetic Theory. . . 41
3.2.2 Simulations . . . 42
3.2.3 Multilayer Planar Junctions . . . 44
3.3 CrO2nanowires . . . 47
3.3.1 magnetic patterns . . . 47
3.3.2 Generating long-range triplets with magnetic pattern . . . 51
References. . . 53
4 Controlling the path of spin-triplet currents in a magnetic multilayer 59 4.1 Introduction . . . 60
4.2 Results . . . 61
4.2.1 Micromagnetic simulations . . . 61
4 CONTENTS
4.2.3 Basic transport properties . . . 63
4.2.4 Superconducting quantum interferometry. . . 63
4.2.5 Magnetotransport with in-plane fields . . . 66
4.3 Discussion . . . 68 4.4 Methods . . . 69 4.4.1 Device fabrication . . . 69 4.4.2 Magnetotransport measurements . . . 69 4.4.3 Micromagnetic simulations . . . 70 4.4.4 Control experiment . . . 70 4.5 Supplementary Information . . . 71 4.5.1 Supplementary Figures . . . 71
4.5.2 Supplementary Note 1: Transport in the virgin state . . . 74
4.5.3 Supplementary Note 2: Numerical simulations of the critical current . . . 74
4.5.4 Supplementary Note 3: Fourier analysis of supercurrent den-sity profiles. . . 76
References. . . 77
5 Generating Spin-Triplet Supercurrents with a Ferromagnetic Vortex 81 5.1 Motivation . . . 82
5.1.1 Formation of 0-π triplet channels: S/F’/F/F”/S . . . 82
5.2 Generating spin-triplet supercurrents with a ferromagnetic vortex . . . 86
5.2.1 Basic transport and ground state interference . . . 86
5.2.2 Magnetotransport with in-plane fields . . . 87
5.2.3 Emergence of 0 &π channels in the vortex . . . 89
5.2.4 Interference patterns from a displaced vortex . . . 89
5.2.5 Summary & Outlook . . . 93
References. . . 95
6 Little-Parks effect and half-quantum fluxoid in Sr2RuO4microrings 97 6.1 Introduction . . . 98
6.2 Results and Discussion . . . 101
References. . . 106
7 Spontaneous emergence of Josephson junctions in Sr2RuO4 111 7.1 General Introduction . . . 112
7.3 Results . . . 115
7.3.1 Basic transport properties . . . 115
7.3.2 Insights from order parameter simulations . . . 116
7.3.3 Critical current oscillations . . . 118
7.3.4 Rings with an extrinsic phase & Tcoscillations . . . 120
7.3.5 Anomalous current-voltage & in-plane fields . . . 124
7.4 Discussion . . . 126
7.4.1 Mechanisms for oscillatory Ic(H ) . . . 126
7.4.2 Josephson energy of a chiral domain wall . . . 128
7.5 Summary & Outlook . . . 134
