Low-temperature lattice effects in the spin-liquid candidate κ-(BEDT-TTF)2Cu2(CN)3

  • The quasi-two-dimensional organic charge-transfer salt κ -(BEDT-TTF) 2 Cu 2 (CN) 3 is one of the prime candidates for a quantum spin-liquid due the strong spin frustration of its anisotropic triangular lattice in combination with its proximity to the Mott transition. Despite intensive investigations of the material’s low-temperature properties, several important questions remain to be answered. Particularly puzzling are the 6 K anomaly and the enigmatic effects observed in magnetic fields. Here we report on low-temperature measurements of lattice effects which were shown to be particularly strongly pronounced in this material (R. S. Manna et al., Phys. Rev. Lett. 2010, 104, 016403)). A special focus of our study lies on sample-to-sample variations of these effects and their implications on the interpretation of experimental data. By investigating overall nine single crystals from two different batches, we can state that there are considerable differences in the size of the second-order phase transition anomaly around 6 K, varying within a factor of 3. In addition, we find field-induced anomalies giving rise to pronounced features in the sample length for two out of these nine crystals for temperatures T< 9 K. We tentatively assign the latter effects to B-induced magnetic clusters suspected to nucleate around crystal imperfections. These B-induced effects are absent for the crystals where the 6 K anomaly is most strongly pronounced. The large lattice effects observed at 6 K are consistent with proposed pairing instabilities of fermionic excitations breaking the lattice symmetry. The strong sample-to-sample variation in the size of the phase transition anomaly suggests that the conversion of the fermions to bosons at the instability is only partial and to some extent influenced by not yet identified sample-specific parameters.

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Author:Rudra Sekhar Manna, Steffi Hartmann, Elena Gati, John A. Schlueter, Valdeci Pereira Mariano de Souza, Michael Lang
URN:urn:nbn:de:hebis:30:3-463921
DOI:https://doi.org/10.3390/cryst8020087
ISSN:2073-4352
Parent Title (English):Crystals
Publisher:MDPI
Place of publication:Basel
Document Type:Article
Language:English
Year of Completion:2018
Date of first Publication:2018/02/06
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2018/05/17
Tag:organic compounds; quantum spin frustration; quantum spin liquids; thermal expansion
Volume:8
Issue:2, Art. 87
Page Number:10
First Page:1
Last Page:10
Note:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
HeBIS-PPN:434239089
Institutes:Physik / Physik
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 53 Physik / 530 Physik
Sammlungen:Universitätspublikationen
Open-Access-Publikationsfonds:Physik
Licence (German):License LogoCreative Commons - Namensnennung 4.0