Low-Temperature Lattice Effects in the Spin-Liquid Candidate κ-(BEDT-TTF)2Cu2(CN)3

被引:12
|
作者
Manna, Rudra Sekhar [1 ,2 ]
Hartmann, Steffi [2 ]
Gati, Elena [2 ]
Schlueter, John A. [3 ,4 ]
de Souza, Mariano [2 ,5 ]
Lang, Michael [2 ]
机构
[1] IIT Tirupati, Dept Phys, Tirupati 517506, Andhra Prades, India
[2] Goethe Univ Frankfurt M, Phys Inst, SFB TR49, D-60438 Frankfurt, Germany
[3] Natl Sci Fdn, Div Mat Res, 4201 Wilson Blvd, Arlington, VA 22230 USA
[4] Argonne Natl Lab, Div Mat Sci, 9700 S Cass Ave, Argonne, IL 60439 USA
[5] Univ Estadual Paulista, Dept Fis, IGCE, BR-13506900 Sao Paulo, Brazil
来源
CRYSTALS | 2018年 / 8卷 / 02期
关键词
quantum spin liquids; quantum spin frustration; organic compounds; thermal expansion; TRIANGULAR-LATTICE; THERMAL-TRANSPORT; STATE; PHASES;
D O I
10.3390/cryst8020087
中图分类号
O7 [晶体学];
学科分类号
0702 ; 070205 ; 0703 ; 080501 ;
摘要
The quasi-two-dimensional organic charge-transfer salt kappa-(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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页数:10
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