Transport and NMR studies of charge glass in organic conductors with quasi-triangular lattices

85 Pages·2017·3.895 MB·English

by  Sato, Takuro

Springer Theses
Recognizing Outstanding Ph.D. Research
Takuro Sato

Transport and NMR
Studies of Charge
Glass in Organic
Conductors with
Quasi-triangular
Lattices
Springer Theses
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Takuro Sato
Transport and NMR
Studies of Charge Glass
in Organic Conductors
with Quasi-triangular Lattices
Doctoral Thesis accepted by
the University of Tokyo, Japan
123
Author Supervisor
Dr. Takuro Sato Prof. KazushiKanoda
RIKENCenterforEmergentMatterScience Department ofApplied Physics
Dynamic EmergentPhenomena Research TheUniversity of Tokyo
Unit Bunkyō,Tokyo
Wako, Saitama Japan
Japan
ISSN 2190-5053 ISSN 2190-5061 (electronic)
SpringerTheses
ISBN978-981-10-5878-3 ISBN978-981-10-5879-0 (eBook)
DOI 10.1007/978-981-10-5879-0
LibraryofCongressControlNumber:2017949126
©SpringerNatureSingaporePte.Ltd.2017
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’
Supervisor s Foreword
The Ph.D. thesis of Takuro Sato is a report on his work which experimentally
demonstrates that an electronic glass emerges on geometrically frustrated lattices.
Glass is a ubiquitous state that appears in atomic or molecular assemblies. Such a
state has been substantiated in electronic systems, as described in this thesis.
TheCoulombrepulsiveforcebetweenelectronsmakesthemlocalizedtoforman
electroniccrystal;however,itsperiodicitydoesnotalwaysmatchthatoftheatomic
ormolecularlattices inmaterials.Thissituation iscalledgeometricalfrustration.If
thelatticeofmaterialsistriangularandelectron(orhole)densityisahalfperlattice
point,thegeometricalfrustrationissostrongthattheelectronsmaynotfindastable
crystal but form a nontrivial state; an electronic glass is a possible state. The
materialsdealtwithinthisthesiswork,layeredorganiccompoundswithanisotropic
triangular lattices, are in such a situation. The hallmarks of the glass state are
nonequilibrium properties, slow dynamics, and short-ranged order; all of them are
captured by the experiments of charge transport, its noise, and X-ray scattering,
respectively, in this work. Furthermore, the phenomena of aging, dynamical
heterogeneity,andcrystalgrowth,whichhavesofarbeenexclusivelytheissuesof
soft matter physics, are observed in strongly correlated electron systems. The
presentworkcreatesanovelinterdisciplinaryplatformthatintegratesthescienceof
correlated electrons and the science of soft matter. It is a great pleasure to me that
Sato’s thesis is published in the Springer theses series.
Tokyo, Japan Prof. Kazushi Kanoda
July 2017
v
Parts of this thesis have been published in the following journal articles:
[1] F. Kagawa, T. Sato, K. Miyagawa, K. Kanoda, Y. Tokura, K. Kobayashi,
R. Kumai, Y. Murakami “Charge-cluster glass in an organic conductor”
Nat. Phys. 9, 2642 (2013)
[2] T. Sato, F. Kagawa, K. Kobayashi, K. Miyagawa, K. Kanoda, R. Kumai,
Y.Murakami,Y.Tokura“Emergenceofnonequilibriumchargedynamicsina
charge-cluster glass” Phys. Rev. B 89, 121102(R) (2014)
[3] T. Sato, F. Kagawa, K. Kobayashi, A. Ueda, H. Mori, K. Miyagawa,
K.Kanoda,R.Kumai,Y.Murakami,Y.Tokura“SystematicVariationsinthe
Charge-Glass-Forming Ability of Geometrically Frustrated h-(BEDT-TTF) X
2
Organic Conductors” J. Phys. Soc. Jpn. 83, 083602 (2014)
[4] T.Sato, K.Miyagawa,K.Kanoda“FluctuationSpectroscopyAnalysisBased
on Dutta-Dimon-Horn Model for the Charge-Glass System h-(BEDT-TTF)
2
CsZn(SCN) ” J. Phys. Soc. Jpn. 85, 123702 (2016)
4
[5] T. Sato, K. Miyagawa, K. Kanoda “Electronic crystal growth” Submitted to
Science (under Review)
vii
Acknowledgements
First ofall, Iwould liketothank K.Kanoda for giving meanopportunity towork
with him on this challenging and exciting project. I am grateful to him for his
numerous and invaluable advice, not only on research, but also on many other
aspects, such as communication and writing.
I would like to express my gratitude to K. Miyagawa for helpful discussions,
continual experimental supports.
I must thank F. Kagawa for not only collaboration but also his continual
encouragement, enlightening suggestions, and critical reading of my papers.
I appreciate fruitful comments and discussions from H. Tanaka, A. Maeda,
Y. Iwasa, and T. Kato.
I am grateful to the excellent technical support by KEK staff, including
Y. Murakami, K. Kumai, and K. Kobayashi.
IwouldliketothankH.MoriandA.Ueda.Theyprovidedhigh-qualitysamples
for this experiment.
IalsothankallthemembersofKanodagroupforhelpfuldiscussionsandsharing
fun.
Finally,Iwouldliketothankmyparentsforkindencouragements.Withoutthe
unconditional support from them, this dissertation would have been impossible.
ix
Contents
1 Background Information . ..... .... .... .... .... .... ..... .... 1
1.1 Introduction .... .... ..... .... .... .... .... .... ..... .... 1
1.2 Organic Conductors .. ..... .... .... .... .... .... ..... .... 3
1.3 h-(BEDT-TTF) X.... ..... .... .... .... .... .... ..... .... 4
2
1.3.1 Crystal Structure.... .... .... .... .... .... ..... .... 4
1.3.2 Geometrical Frustration... .... .... .... .... ..... .... 5
1.3.3 Previous Experimental Studies of h-(BEDT-TTF) X.. .... 7
2
1.3.4 Previous Phase Diagram for h-(BEDT-TTF) X. ..... .... 13
2
1.3.5 New Possibility in Terms of Geometrical Frustration . .... 13
1.4 Classical Glass .. .... ..... .... .... .... .... .... ..... .... 13
1.4.1 Phenomenology of Supercooled Liquids.. .... ..... .... 15
1.4.2 Structural Dynamics in Glass-Forming Systems ..... .... 16
1.4.3 Time-Dependent Relaxation Process. .... .... ..... .... 17
1.4.4 Critical Cooling Rate .... .... .... .... .... ..... .... 18
1.5 Purpose of the Thesis. ..... .... .... .... .... .... ..... .... 19
References.. .... .... .... ..... .... .... .... .... .... ..... .... 20
2 Experimental... .... .... ..... .... .... .... .... .... ..... .... 23
2.1 Sample Preparation... ..... .... .... .... .... .... ..... .... 23
2.2 Resistivity Measurements... .... .... .... .... .... ..... .... 23
2.3 Resistance Noise Measurements.. .... .... .... .... ..... .... 24
2.4 X-Ray Diffuse Scattering Measurements.... .... .... ..... .... 26
2.5 NMR Measurements.. ..... .... .... .... .... .... ..... .... 28
References.. .... .... .... ..... .... .... .... .... .... ..... .... 33
3 Charge-Glass State in h-(BEDT-TTF) X.. .... .... .... ..... .... 35
2
3.1 Introduction .... .... ..... .... .... .... .... .... ..... .... 35
3.2 Hallmarks of Charge Glass in h-(BEDT-TTF) CsZn(SCN) .. .... 36
2 4
3.2.1 Non-equilibrium Nature in Charge-Glass State . ..... .... 36
3.2.2 Slow Dynamics in Charge-Liquid State .. .... ..... .... 39
xi
xii Contents
3.2.3 Distribution of Activation Energy in Slow Charge
Dynamics .... ..... .... .... .... .... .... ..... .... 43
3.2.4 Evolution of Short-Ranged Charge-Ordered Domains. .... 48
3.3 The Effect of Geometrical Frustration on the Glassy
Behaviors.. .... .... ..... .... .... .... .... .... ..... .... 50
3.3.1 Charge-Glass State and Its Fragility
in h-(BEDT-TTF) RbZn(SCN) .... .... .... ..... .... 50
2 4
3.3.2 Evolution of Short-Ranged Spatial Order
in h-(BEDT-TTF) RbZn(SCN) .... .... .... ..... .... 53
2 4
3.4 The Effect of Geometrical Frustration
on Charge-Glass-Forming Ability. .... .... .... .... ..... .... 55
3.4.1 Stability of the Charge-Ordered State
in h-(BEDT-TTF) TlCo(SCN) . .... .... .... ..... .... 55
2 4
3.4.2 Systematic Variation of the Charge-Glass-Forming
Ability... .... ..... .... .... .... .... .... ..... .... 58
3.5 Summary .. .... .... ..... .... .... .... .... .... ..... .... 60
References.. .... .... .... ..... .... .... .... .... .... ..... .... 61
4 Electronic Crystal Growth ..... .... .... .... .... .... ..... .... 63
4.1 Introduction .... .... ..... .... .... .... .... .... ..... .... 63
4.2 Experimental.... .... ..... .... .... .... .... .... ..... .... 65
4.3 Time-Temperature-Transformation Curve in Resistivity
Growth.... .... .... ..... .... .... .... .... .... ..... .... 65
4.4 Formation of Intermediate State Before CO Nucleation ..... .... 68
4.5 Summary .. .... .... ..... .... .... .... .... .... ..... .... 73
References.. .... .... .... ..... .... .... .... .... .... ..... .... 74
5 Conclusions .... .... .... ..... .... .... .... .... .... ..... .... 75
About the Author .. .... .... ..... .... .... .... .... .... ..... .... 77