Nuclear Spectroscopy on Charge Density Wave Systems

333 Pages·1992·11.171 MB·English

by  Tilman Butz (auth.), Tilman Butz (eds.)

NUCLEAR SPECTROSCOPY ON CHARGE DENSITY WAVE SYSTEMS
Physics and Chemistry of Materials
with Low-Dimensional Structures
VOLUME 15
Editor-in-Chief
F. LEVY, Institut de Physique Appliquee, EPFL,
Departement de Physique, PHB-Ecublens, CH-IOI5 Lausanne, Switzerland
Honorary Editor
E. MOOSER, EPFL, Lausanne, Switzerland
International Advisory Board
J. V. ACRIVOS, San Jose State University, San Jose, Calif., U.S.A.
S. BARISIC, University of Zagreb, Department of Physics, Zagreb, Yugoslavia
J. G. BEDNORZ, IBM Forschungslaboratorium, Ruschlikon, Switzerland
C. F. van BRUGGEN, University ofGroningen, Groningen, The Netherlands
R. GIRLANDA, Universita di Messina, Messina, Italy
D. HAARER, University of Bayreuth, Germany
A. J. HEEGER, University of California, Santa Barbara, Catif., U.S.A.
H. KAMIMURA, Dept. of Physics, University of Tokyo, Japan
W. Y. LIANG, Cavendish Laboratory, Cambridge, u.K.
P. MONCEAU, CNRS, Grenoble, France
J. ROUXEL, CNRS, Nantes, France
M. SCHLUTER, AT&T, Murray Hill, N.J., U.S.A.
I. ZSCHOKKE, Universitiit Basel, Basel, Switzerland
The titles published in this series are listed at the end of this volume.
NUCLEAR SPECTROSCOPY ON
CHARGE DENSITY WAVE SYSTEMS
Edited by
Tilman Butz
Physics Department,
Technische Universitiit Munchen,
Garching, Germany
KLUWER ACADEMIC PUBLISHERS
DORDRECHT / BOSTON / LONDON
Library of Congress Cataloging-in-Publication Data
Nuclear spectroscopy on charge dens1ty wave systems / ed1ted by T1 lman
Butz.
p. cm. -- (Phys1cs and chem1stry of mater1als w1th low
-d1mens1onal structures; v. 15)
Pap e r s fro maw 0 r k Sh op he 1d 1n B a v a r 1a 1n 1989.
Includes b1bl1ographlcal references and Index.
ISBN 978-90-481-4165-4 ( a 1k . pap e r )
1. Charge densIty waves. 2. Sol1d state phYS1CS. 3. Nuclear
spectroscopy. I. Butz. T 11 man. II. Ser 1e s.
QC17S.8.E4N83 1992
530.~· 1--dc20 92-12827
ISBN 978-90-481-4165-4 ISBN 978-94-015-1299-2 (eBook)
DOI 10.1007/978-94-015-1299-2
Published by Kluwer Academic Publishers,
P.O. Box 17, 3300 AA Dordrecht, The Netherlands.
Kluwer Academic Publishers incorporates
the publishing programmes of
D. Reidel, Martinus Nijhoff, Dr W. Junk and MTP Press.
Sold and distributed in the U.S.A. and Canada
by Kluwer Academic Publishers,
101 Philip Drive, Norwell, MA 02061, U.S.A.
In all other countries, sold and distributed
by Kluwer Academic Publishers Group,
P.O. Box 322, 3300 AH Dordrecht, The Netherlands.
Printed on acid-free paper
All Rights Reserved
© 1992 Kluwer Academic Publishers
Softcover reprint of the hardcover 1st edition 1992
No part of the material protected by this copyright notice may be reproduced or
utilized in any form or by any means, electronic or mechanical,
including photocopying, recording or by any information storage and
retrieval system, without written permission from the copyright owner.
Table of Contents
Preface........................................................... xi
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
TILMAN BUTZ
Phenomenological Theory of Charge-Density-Wave Phase Transitions
in the NbTe4 - TaTe4 Series of Compounds. . . . . . . . . . . . . . . . . . . . . . . . 7
MICHAEL B. WALKER
1. Introduction .................................................... 7
2. A Prototypical Model of Charge-Density-Wave Formation ...... 8
2.1. The Order Parameter, Symmetry Considerations, and the Free Energy 8
2.2. Commensurate and Incommensurate Phases ...................... 11
2.3. The Nuclear Hyperfine Interaction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 16
2.4. Dynamics of the Modulation Wave. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3. Modulated Structures of the NbTe4 Series of Compounds. . . . . . . 21
3.1. Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.2. The Free Energy of a Charge-Density Wave on a Single Column. . . .. 24
3.3. Commensurate Phases of TaTe4 ................................. 25
3.4. Incommensurate Phases of NbTe4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27
3.5. The Nuclear Hyperfine Interaction. . . . . . . . . . . .. . . . . . . . . . . . . . . . . .. 30
4. Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 31
Layered Transition Metal Dichalcogenides ........................ , 35
MICHIO NAITO, HIRONORI NISHIHARA, AND TILMAN BUTZ
1. Hyperfine Techniques ........................................... 35
1.1. NMR ........................................................ 36
1.2. NQR and Quadrupole Effects in NMR ........................... 40
1.2.1. The Case of Zero Applied Magnetic Field (H=O) ............. 42
1.2.2. The Case of a Weak Magnetic Field ........................ 43
1.2.3. The Case of a Strong Magnetic Field ....................... 46
vi
1.3. TDPAC ........... . . . . . . . . . . . . .. .. . . . . . .. .. . . . . . . . . .. . . . . . . .. 47
1.4. Mossbauer Effect. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 51
1.4.1. The Isomer Shift. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 52
1.4.2. Line Splittings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 52
2. Structure of Layered Transition Metal Dichalcogenides . . . . . . . . .. 54
3. Compounds with Octahedral Metal Coordination ........ . . . . . .. 56
3.1. 1T-TiSe2 ..................................................... 56
3.2. 1T-VSe2...................................................... 59
3.3. Tantalum Dichalcogenides ............................ . . . . . . . . .. 64
3.3.1.1T-TaSe2 ................................................ 68
3.3.2. IT- TaS2 ................................................ 75
4. Compounds with Trigonal Prismatic Metal Coordination.. . . . . .. 85
4.1. Tantalum Dichalcogenides ...................................... 85
4.1.1.2H-TaSe2 ............................................... 85
4.1.2.2H-TaS2 ................................................ 98
4.2. 2H-NbSe2 .................................................... 102
5. Compounds with Mixed Metal Coordination. . . . . . . . . . . . . . . . . . .. 106
Nuclear Spectroscopy Studies of Quasi-one-dimensional
Transition Metal Chalcogenides. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 113
JOSEPH H. Ross, JR. AND CHARLES P. SLICHTER
1. Introduction .................................................... 113
1.1. Nuclear Spectroscopy Techniques. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 113
1.2. Materials ..................................................... 115
1.3. CDW Conductivity Effects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 117
1.3.1. CDW Pinning ........................................... 118
1.3.2. Models for CDW Motion .................................. 119
2. NbSes ........ , .................................................. 125
2.1. NbSe3 Normal-State Spectra. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 126
2.2. Site Identification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 129
2.3. CDW Transitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 130
2.4. Knight Shifts and Susceptibilities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 135
2.5. Spin-Lattice Relaxation ........................................ 139
2.6. NMR of the Moving CDW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 142
2.6.1. NMR Sample. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 142
2.6.2. Motional Narrowing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 143
2.6.3. Current-induced Saturation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 149
2.6.4. Pulsed CDW Displacements ............................. " 151
2.7. Pressure and Impurity Effects ................................... 153
3. Monoclinic TaSs ................................................ 155
3.1. Room-temperature Measurements ............................... 155
vii
3.2. CDW Transitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 157
3.3. Magnetic Field Effects ......................................... 160
4. FeNb3Selo ...................................................... 160
5. Tetrachalcogenides .............................................. 165
5.1. (NbSe4hI .................................................... 166
5.2. (NbSe4ho/3I .................................................. 168
6. Conclusions ..................................................... 169
Nuclear Spectroscopy of Charge Density Waves
in Molybdenum Bronzes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 177
CLAUDE BERTHIER, ANDRAS JANOSSY+, PATRICK BUTAUD I
AND PIERRE SEGRANSAN
1. Introduction .................................................... 177
2. Physical Properties of the Blue Bronzes. . . . . . . . . . . . . . . . . . . . . . . .. 178
2.1. Crystal Structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 178
2.2. The Peierls Transition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 178
2.3. Dynamics of the CDW ......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 181
2.3.1. Excitations at Finite Frequencies. . . . . . . . . . . . . . . . . . . . . . . . . .. 181
2.3.2. The Frohlich Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 181
2.3.3. Voltage Oscillations ...................................... 184
3. NMR in the Normal State ...................................... 187
3.1. Electric Field Gradient and Magnetic Hyperflne Shift Tensors. . . . . .. 188
3.2. Quasi-1D properties. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 190
4. Nuclear Spectroscopy of Pinned CDW .......................... 190
4.1. Lineshape in Presence of an Incommensurate CDW ................ 191
4.1.1. Nuclear Magnetic Resonance Lineshape ..................... 191
4.1.2. Temperature Dependence of the Order Parameter ............ 192
4.1.3. Electron Paramagnetic Resonance (EPR) in Inorganic
CDW Systems ........................................... 193
4.2. Commensurability of the CDW with the Lattice ................. " 195
4.3. ESR and Mossbauer Studies of the Strength of the CDW
impurity pinning .............................................. 200
4.4. Defect Density Waves .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 201
4.5. Metastable States and EPR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 201
5. Dynamics in the Pinned CDW .................................. 202
6. NMR in the Sliding CDW State ................................ 206
6.1. Introduction .................................................. 206
6.2. Theory of NMR under CDW Current ............................ 206
6.2.1. NMR Spectra for a Sliding CDW ........................... 206
6.2.2. Spin-echo in Presence of a Sliding CDW ..................... 210
viii
6.2.3. Stochastic Fluctuations of the Velocity;
Spin-Spin Relaxation Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 210
6.3. Determination of the CDW Phase Velocity. . . . . . . . . . . . . . . . . . . . . . .. 211
6.4. Inhomogeneity of the Threshold Field for Depinning ............... 217
6.5. Temporal Fluctuations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 219
7. Conclusion ............................................. , ........ 222
NMR Studies of the Quasi One-dimensional Inorganic Complex Salt
K2Pt(CN)4Bro.s3.2H20 (KCP) .................................... 229
DETLEF BRINKMANN AND OTMAR KANERT
1. Introduction .................................................... 229
2. Properties of KCP .................... . . . . . . . . . . . . . . . . . . . . . . . . .. 230
2.1. Lattice Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 230
2.2. Peierls Transition and CDW .................................... 233
2.3. Solitary Excitation Modes of CDW .............................. 234
3. NMR Investigations in KCP .................................... 237
3.1. Introductory Remarks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 237
3.2. Properties of the Conducting Chains by 195pt NMR ............... 239
3.2.1. NMR Spectrum and Chemical Shift below 120 K ............. 239
3.2.2. Knight Shift and Relaxation above 120 K ................... 244
3.2.3. Relaxation beween 30 and 120 K . . . . . . . . . . . . . . . . . . . . . . . . . .. 248
3.3. Lattice Fluctuations near the 3D Ordering Transition by 14N NMR .. 256
3.4. 13C Chemical Shift and Relaxation .............................. 259
3.5. Sites and Motion of Water Molecules by 1H NMR ................. 261
3.6. Sites and Dynamics of Bromine by 81 Br and 39K NMR . . . . . . . . . . . .. 266
4. Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 270
High Resolution NMR on Organic Radical Salts. . . . . . . . . . . . . . . . . .. 275
MICHAEL HELMLE AND MICHAEL MEHRING
1. Introduction .................................................... 275
2. Solid State Theory of Radical Salts ............................. 276
2.1. Simple Band Models ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 276
2.2. Instabilities in One-Dimensional Systems ......................... 279
3. High Resolution Techniques. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 280
3.1. The Need for High Resolution Techniques ......................... 280
3.2. Double Resonance and Magic Angle Spinning ..................... 280
3.3. Multiple Pulse Techniques .................................... " 283
4. Magnetic Electron Nuclear Interaction ................. , ........ 283
4.1. Closed Shell Interactions ....................................... 283
4.2. Open Shell Interactions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 284
ix
4.3. Time Averaged Hyperfine Interaction ............................ 284
4.4. Hyperfine Interaction in Organic Molecules ....................... 285
4.5. Hyperfine Fluctuations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 287
5. Experimental Results ........................................... 288
5.1. Local Hyperfine Interaction and Spin Density Distribution .......... 288
5.2. Magnetic Susceptibility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 292
5.3. Localized States and Disorder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 293
5.4. Charge and Spin Transfer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 298
5.5. One-dimensional Transport ..................................... 298
5.6. Phase Transition in (FAhX ..................................... 300
5.7. Phase Transition in (TMTSFhRe04 ............................. 301
5.8. Phase Transition in TTF[Ni( dmit hh . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 303
5.9. Spin Peierls Transition .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 303
5.10. SDW transition .............................................. 304
5.11. CDW Transition .............................................. 305
6. Summary ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 307
Index ............................................................. . 313
PREFACE
This book is the first coherent presentation of investigations of charge density
wave (CDW) systems by nuclear spectroscopic techniques. It belongs to the series
"Physics and Chemistry of Materials with Low-Dimensional Structures" published
by Kluwer Academic Publishers. It addresses the following readership: graduate
students and elder scientists with an education in physics and chemistry who are
interested in modern aspects of solid state physics and want to acquire a broader
knowledge of nuclear spectroscopy techniques applied to CDW systems; experts in
the field of CDW's who are familiar with a dozen of modern techniques but never
bestowed all their affections on nuclear spectroscopy techniques; active researchers
in the field of one of the nuclear spectroscopy techniques applied to CDW systems
who wish to learn that even this highly specialized topic - which certainly does not
deserve a separate entry in the physics and astronomy classification scheme - is full
of surprises "next door".
The limited space of this volume necessitated a number of restrictions: first, a
selection of systems had to be made which was guided by the concept of discussing
a few systems thorougly studied by nuclear spectroscopy techniques in greater de
tail rather than to present an incoherent collection of data; secondly the reader is
advised to make extensive use of previous books in this series because it would not
have made sense to repeat the content here.
Chapter 1 gives a short introduction to CDW's in general and to the question
what can be learned about CDW's by nuclear spectroscopy techniques. Chapter
2 gives a Landau theory description of CDW formation in chain-like tetrachalco
genides. This chapter is intended to elucidate the essential ingredients into a theo
retical description of a prototypical system and should stimulate a rigorous research
activity on these substances by nuclear spectroscopy techniques. For CDW theories
on layered transition metal compounds, the reader is referred to the book "Struc
tural Phase Transitions in Layered Transition Metal Compounds", K. Motizuki
(ed.) in the same series. Chapter 3 treats experimental resuls on layered transition
metal compounds. A short introduction to nuclear magnetic resonance (NMR),
nuclear quadrupole resonance (NQR), time differential perturbed angular correla
tion (TDPAC), and the Mossbauer effect (ME) is included in this chapter because
all three techniques have been extensively applied to Ta-dichalcogenides which are
prominent members of this family of materials. Whereas chapter 3 in mainly con
cerned with static aspects of CDW's, chapter 4 and 5 treat in great detail CDW dy
namics and CDW transport in chain-like transition metal chalcogenides and molyb-
xi