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Electron Spin Resonance Study of Organic Conductors

English title Electron Spin Resonance Study of Organic Conductors
Applicant Forro Laszlo
Number 144419
Funding scheme Project funding
Research institution Institut de physique de la matière condensée EPFL - SB - ICMP
Institution of higher education EPF Lausanne - EPFL
Main discipline Condensed Matter Physics
Start/End 01.10.2013 - 30.09.2017
Approved amount 263'226.00
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Keywords (4)

quantum spin liquid; chemical pressure; electron spin resonance; high pressure

Lay Summary (French)

Lead
Les interactions fortes entres les électrons présents dans un métal peuvent engendrer des états ordonnés comme isolant anti-ferromagnétique ou supraconducteur. En revanche dans certains cas ces interactions peuvent détruire l’ordre à grande échelle entraînant l’apparition d’un nouvel état de matière comme le non liquide de Fermi ou le longuement cherché état de liquide de spin. L’étude de l’état de liquide de spin dans des composants organiques est le thème central du projet qui suit.
Lay summary

Les liquides de spin émergent de fluctuations quantiques fortes à basse température et sont par la suite accentués par le fait de travailler à dimension faible. Des prédictions indiquent leur existence en deux dimensions pourtant il est rare de voir de bonne réalisation physique de tel systèmes. Récemment deux familles de sels organiques à transfert de charge, κ-(BEDT-TTF)2Cu2(CN)3 et EtMe3Sb[Pd(dmit)2]2 se sont révélés en utilisant des techniques expérimentales diverses avoir un état fondamental de liquide de spin. Pourtant, les résultats expérimentaux et l’attribution du déclencheur à l’origine de l’état de liquide de spin sont controversés. Les descriptions théoriques évoquent deux modèles en concurrence fondamentalement distincts. L’un est basé sur l’isolant de Mott moitié-plein dans lequel une délicate interaction d’effets de corrélation et de frustration géométrique conduit le système à un état de liquide de spin. L’autre modèle décrit le système comme un matériel avec bandes au quart remplies où les fluctuations électroniques entres molécules adjacentes se couplent fortement aux degrés de libertés du spin et expliquent la suppression de l’ordre magnétique.

Quelles sont les anisotropies intrinsèques at comment le liquide de spin passe de la phase métallique à supraconductrice est le sujet central de ce projet. Nous allons étudier ces liquides organiques de spin par résonance paramagnétique électronique (RPE). La RPE est une sonde extrêmement sensible localement que ce soit pour détecter les corrélations magnétiques ou les anisotropies. Nos études uniques par la précision extrême de notre RPE en conditions ambiante et hydrostatique de pression vont répondre à ces questions. Nous cherchons également des réponses aux problèmes tels que comment les fluctuations électroniques d’un dipôle se couplent-elles aux degrés de libertés de charge et de spin et comment influencent-elles celles magnétiques à basse température.

Direct link to Lay Summary Last update: 04.12.2013

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
Superior Water Sheeting Effect on Photocatalytic Titania Nanowire Coated Glass
Náfrádi Bálint, Náfrádi Gábor, Martin-Hamka Carole, Forró László, Horváth Endre (2017), Superior Water Sheeting Effect on Photocatalytic Titania Nanowire Coated Glass, in Langmuir, 33(36), 9043-9049.
Doped carbon nanotubes as a model system of biased graphene
Szirmai P., Márkus B. G., Dóra B., Fábián G., Koltai J., Zólyomi V., Kürti J., Náfrádi B., Forró L., Pichler T., Simon F. (2017), Doped carbon nanotubes as a model system of biased graphene, in Physical Review B, 96(7), 075133-075133.
Cyan titania nanowires: Spectroscopic study of the origin of the self-doping enhanced photocatalytic activity
Szirmai Péter, Náfrádi Bálint, Arakcheeva Alla, Szilágyi Edit, Gaál Richárd, Nemes Norbert M., Berdat Xavier, Spina Massimo, Bernard Laurent, Jaćimović Jaćim, Magrez Arnaud, Forró László, Horváth Endre (2017), Cyan titania nanowires: Spectroscopic study of the origin of the self-doping enhanced photocatalytic activity, in Catalysis Today, 284, 52-58.
Competitive ion-exchange of manganese and gadolinium in titanate nanotubes
Szirmai Peter, Stevens Jeremy, Horvath Endre, Ciric Luka, Kollar Marton, Forro Laszlo, Nafradi Balint (2017), Competitive ion-exchange of manganese and gadolinium in titanate nanotubes, in CATALYSIS TODAY, 284, 146-152.
Frustration-induced one-dimensionality in the isosceles triangular antiferromagnetic lattice of δ -(EDT-TTF- CONMe2)2AsF6
Náfrádi B., Antal Á., Fehér T., Kiss L. F., Mézière C., Batail P., Forró L., Jánossy A. (2016), Frustration-induced one-dimensionality in the isosceles triangular antiferromagnetic lattice of δ -(EDT-TTF- CONMe2)2AsF6, in Physical Review B, 94(17), 174413-174413.
Anisotropic Elliott-Yafet theory and application to KC8 potassium intercalated graphite
Markus Bence G., Szolnoki Lenard, Ivan David, Dora Balazs, Szirmai Peter, Nafradi Balint, Forro Laszlo, Simon Ferenc (2016), Anisotropic Elliott-Yafet theory and application to KC8 potassium intercalated graphite, in PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, 253(12), 2505-2508.
Optically switched magnetism in photovoltaic perovskite CH3NH3(Mn:Pb)I-3
Nafradi B., Szirmai P., Spina M., Lee H., Yazyev O. V., Arakcheeva A., Chernyshov D., Gibert M., Forro L., Horvath E. (2016), Optically switched magnetism in photovoltaic perovskite CH3NH3(Mn:Pb)I-3, in NATURE COMMUNICATIONS, 7, 13406.
Room temperature manipulation of long lifetime spins in metallic-like carbon nanospheres
Nafradi Balint, Choucair Mohammad, Dinse Klaus-Peter, Forro Laszlo (2016), Room temperature manipulation of long lifetime spins in metallic-like carbon nanospheres, in NATURE COMMUNICATIONS, 7, 12232.
Ultrasensitive 1D field-effect phototransistors: CH3NH3PbI3 nanowire sensitized individual carbon nanotubes
Spina M., Nafradi B., Tohati H. M., Kamaras K., Bonvin E., Gaal R., Forro L., Horvath E. (2016), Ultrasensitive 1D field-effect phototransistors: CH3NH3PbI3 nanowire sensitized individual carbon nanotubes, in NANOSCALE, 8(9), 4888-4893.
Methylammonium Lead Iodide for Efficient X-ray Energy Conversion
Nafradi Balint, Nafradi Gabor, Forro Laszlo, Horvath Endre (2015), Methylammonium Lead Iodide for Efficient X-ray Energy Conversion, in JOURNAL OF PHYSICAL CHEMISTRY C, 119(45), 25204-25208.

Collaboration

Group / person Country
Types of collaboration
Prof. Henrik Ronnow Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Dr. Claude Coullon France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Prof. Thierry Giamarchi Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Prof. Patrick Batail France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
Prof. Frederic Mila Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Prof. Andras Janossy Hungary (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel
Dr. Natalia Kushch Russia (Europe)
- in-depth/constructive exchanges on approaches, methods or results

Associated projects

Number Title Start Funding scheme
177005 Novel Sample Environment for the µSR Spectrometer FLAME 01.11.2018 R'EQUIP
124723 Electron Spin Resonance study of organic conductors 01.04.2009 Project funding

Abstract

Strong correlations between electrons in metals can lead to ordered states like anti-ferromagnetic insulator or superconductor. On the other hand in some cases correlations may destroy the long-range order resulting in another novel state of matter like the non-Fermi-liquid or the long-sought spin liquid state. The study of the spin liquid state in low-dimensional organic compounds is the central theme of the present proposal. This will be the continuation and extension of our ongoing work on low-dimensional organic magnets and conductors.Spin liquids emerge from strong quantum fluctuations at low temperatures and are further enhanced by the low-dimensionality. They are predicted to exist in two dimensions as well [Anderson1973], however good physical realizations are rare. Recently, two family of organic charge transfer salts, kappa-(BEDT-TTF)2Cu2(CN)3 and EtMe3Sb[Pd(dmit)2]2 [Shimizu2003, Itou2008] were identified using various experimental techniques as having spin liquid ground state. However, the experimental findings and the attribution of the driving force for the spin liquid state are controversial. Theoretical descriptions evoke two competing, fundamentally distinct models. One is based on a half-filled Mott insulator where a delicate interplay of correlation effects and geometrical frustration drive the system into a spin liquid state. The other one describes the system as a quarter filled band material, where electronic fluctuations between adjacent molecules strongly couple to the spin degrees of freedom and account for the suppression of the magnetic order. However, none of these models include the Dzyaloshinsky-Moriya (DM) interaction which might be an important ingredient.Here we propose Electron Spin Resonance (ESR) spectroscopy studies of these organic spin liquid materials. ESR is an extremely sensitive local probe for both magnetic correlations and anisotropies. Contrasting ESR results on kappa-(BEDT-TTF)2Cu2(CN)3 and EtMe3Sb[Pd(dmit)2]2 will clarify the importance of band filling, electric dipole fluctuations and geometrical frustration effects. Furthermore, since DM interaction is absent in EtMe3Sb[Pd(dmit)2]2 while allowed by symmetry in kappa-(BEDT-TTF)2Cu2(CN)3 our ESR results will help to identify the importance of such an anisotropy.One of the theories stresses the importance of charge fluctuations. Complementing these studies, we will also investigate a unique molecular-conductor molecular-rotor hybrid material, (EDT-TTF-CONH2)2(BABCO). Here an accurate control of the electric dipole fluctuations coupled to the spin degrees of freedom can be studied.
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