Unconventional superconductivity in 
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-(BETS)
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 probed by 
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Kobayashi, Takamichi; Taniguchi, Hiromi; Ohnuma, A.; Kawamoto, Atsushi

doi:10.1103/physrevb.102.121106

Cited by 10 publications

(7 citation statements)

References 40 publications

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“…Regarding the physical properties derived from the spin degree of freedom, λ-(BETS) 2 GaBr x Cl 4−x with x = 0.75 exhibits divergence of the spin-lattice relaxation rate divided by temperature (T 1 T ) −1 with a metal-insulator transition at 13 K, indicating spin-density wave (SDW) ordering [23]. The salt with x = 0.75 is located much closer to the SC salt λ-(BETS) 2 GaCl 4 (x = 0) in the phase diagram of λ-(BETS) 2 GaBr x Cl 4−x [24,25]; in the latter, (T 1 T ) −1 increases with a decrease in temperature below 10 K when the superconductivity is suppressed by the magnetic field [21,26,27]. Therefore, an increase in (T 1 T ) −1 of the SC salt is considered to represent the spin fluctuation derived from the adjacent SDW phase.…”

Section: Introductionmentioning

confidence: 90%

Selective observation of spin and charge dynamics in an organic superconductor λ−(BETS)2GaCl4 using Ga

et al. 2020

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For the unconventional organic superconductor λ-(BETS) 2 GaCl 4 [BETS = bis(ethylenedithio) tetraselenafulvalene], the importance of both spin and charge degrees of freedom has been discussed based on the broadening of the NMR linewidth due to charge disproportionation and the occurrence of a spin-density-wave phase near the superconducting phase. NMR with the nuclear spin of 1/2, previously used for studying organic conductors, is an effective method for revealing electronic states microscopically; however, it cannot distinguish between charge and spin anomalies. To resolve this problem, in this paper, we performed 69,71 Ga-NMR measurements, which enabled us to study both charge and spin dynamics using different gyromagnetic ratios and quadrupole moments between two isotopes. The spin-lattice relaxation rate is dominated by electric-field gradient fluctuations originating from molecular dynamics above 150 K and, below this temperature, it is dominated by spin fluctuations derived from the π electrons of BETS layers. This change in the relaxation mechanism is considered to be due to the development of interactions between GaCl 4 ions and BETS layers upon freezing of the molecular motion by cooling. Below 150 K, the contribution of spin fluctuations monotonically increases, and no increase in the charge fluctuation was observed, suggesting that the spin degree of freedom plays a major role in low-temperature physical properties. Our findings will aid theoretical studies on superconducting properties.

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Section: Introductionmentioning

confidence: 90%

Selective observation of spin and charge dynamics in an organic superconductor λ−(BETS)2GaCl4 using Ga

et al. 2020

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“…Thus the shortest distances of d 1 and d 2 from the chalcogens in ordered B (B ) molecules to the Cl atom are realized, suggesting the formation of interaction paths between donor molecules and anions. Indeed, 69,71 Ga NMR in isostructural λ-(BETS) 2 GaCl 4 revealed that Bloembergen-Purcell-Pound-type molecular motion was observed at room temperature and frozen at around 100 K [27].…”

Section: A X-ray Diffractionmentioning

confidence: 99%

“…λ-(BETS) 2 GaCl 4 undergoes a superconducting (SC) transition at around 6 K [5][6][7]. Thermodynamic and 13 C nuclear magnetic resonance (NMR) studies revealed that λ-(BETS) 2 GaCl 4 has d-wave SC gap symmetry [8,9]. A Fulde-Ferrell-Larkin-Ovchinnikov state has been suggested near the upper critical field [6,7,10,11].…”

Section: Introductionmentioning

confidence: 99%

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Magnetic state in the quasi-two-dimensional organic conductor λ−(BEST)2FeCl4 and the path of π−d
Saito
¹
,
Iida
²
,
Kobayashi
³

et al. 2022
Phys. Rev. B
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Studies of the quasi-two-dimensional organic conductors λ-(D) 2 MCl 4 [D = donor molecules, M = Ga, Fe] have shown that λ-(BETS) 2 GaCl 4 [BETS = bis(ethylenedithio)tetraselenafulvalene] undergoes an unconventional superconducting transition and λ-(BETS) 2 FeCl 4 undergoes a field-induced superconducting transition. In λ-type salts, the interactions between donor molecules and FeCl − 4 (π -d interactions) are important.To investigate π -d interaction, a pair of magnetic M = Fe and nonmagnetic M = Ga salts which have the same ground state in the donor layer is desired. However, no such pair has been found, and few experimental studies have considered π -d interaction paths. λ-(BEST) 2 MCl 4 [BEST = bis(ethylenediseleno)tetrathiafulvalene] are obtained for both anions, and M = Ga salt shows an antiferromagnetic transition, but the ground state has not been analyzed in M = Fe salt. We perform x-ray diffraction, magnetic susceptibility measurement, and Mössbauer spectroscopy in λ-(BEST) 2 FeCl 4 . We find that a magnetic transition is observed at around 26 K. The λ-(BEST) 2 MCl 4 system is a system in which both FeCl − 4 and GaCl − 4 salts show antiferromagnetic transitions. In addition, the ethylene motions observed at room temperature are ordered around 108 K, resulting in the establishment of the π -d interaction path between chalcogens and the anion, and low-field magnetization suggests that the π -d interaction in λ-(BEST) 2 FeCl 4 is smaller than that in λ-(BETS) 2 FeCl 4 . Our results show that the inner chalcogen of donor molecules is important as the path of the interaction.

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“…λ-(BEDT-TSF) 2 M Cl 4 [BEDT-TSF (BETS): bis(ethylenedithio)tetraselenafulvalene (Fig. 1(a)-ii), M = Ga, Fe] also exhibit interesting properties such as field-induced superconductivity [12], Fulde-Ferrell-Larkin-Ovchinnikov superconductivity [13][14][15], and an anisotropic superconducting gap [16][17][18][19]. Therefore, they should be investigated in addition to the abovementioned compounds.…”

Section: Introductionmentioning

confidence: 99%

Antiferromagnetic ordering of organic Mott insulator $λ$-(BEDSe-TTF)$_2$GaCl$_4$

Ito,

Kobayashi,

Sari

et al. 2021

Preprint

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The band structure and magnetic properties of organic charge-transfer salt λ-(BEDSe-TTF)2GaCl4 (BEDSe-TTF: bis(ethylenediseleno)tetrathiafulvalene, abbreviated as λ-BEDSe) were investigated. The reported crystal structure was confirmed by the X-ray diffraction measurement, and the transfer integrals were calculated. The degree of electron correlation U/W (U : on-site Coulomb repulsion, W : bandwidth) of λ-BEDSe is larger than one and comparable to that of isostructural Mott insulator λ-(ET)2GaCl4 (ET: bis(ethylenedithio)tetrathiafulvalene, abbreviated as λ-ET), whereas U/W of superconducting salt λ-(BETS)2GaCl4 (BETS: bis(ethylenedithio)tetraselenafulvalene) is smaller than one. 13 C-NMR and µSR measurements revealed that λ-BEDSe undergoes an antiferromagnetic (AF) ordering below TN = 22 K. In the AF state, discrete 13 C-NMR spectra with a remaining central peak were observed, indicating the commensurate AF spin structure also observed in λ-ET. The similarity between structural and magnetic properties of λ-BEDSe and λ-ET indicates that both salts are in the same electronic phase, namely, physical properties of λ-BEDSe can be understood by the universal phase diagram of bandwidthcontrolled λ-type organic conductors by donor molecule substitution. Furthermore, polymorphism was not obtained in the synthesis of this material, unlike for many other λ-type salts. The absence of polymorphism will allow us to construct electronic phases next to the superconducting phase, where a strange paramagnetic insulating phase is sandwiched between superconducting and antiferromagnetic phases.

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Unconventional superconductivity in λ -(BETS) 2GaCl4 probed by C13<

Cited by 10 publications

References 40 publications

Selective observation of spin and charge dynamics in an organic superconductor λ−(BETS)2GaCl4 using Ga

Selective observation of spin and charge dynamics in an organic superconductor λ−(BETS)2GaCl4 using Ga

Magnetic state in the quasi-two-dimensional organic conductor λ−(BEST)2FeCl4 and the path of π−d
Saito
¹
,
Iida
²
,
Kobayashi
³

et al. 2022
Phys. Rev. B
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3
0
8
0
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Antiferromagnetic ordering of organic Mott insulator $λ$-(BEDSe-TTF)$_2$GaCl$_4$

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Unconventional superconductivity in λ -(BETS) 2GaCl4 probed by C13<

Cited by 10 publications

References 40 publications

Selective observation of spin and charge dynamics in an organic superconductor λ−(BETS)2GaCl4 using Ga

Selective observation of spin and charge dynamics in an organic superconductor λ−(BETS)2GaCl4 using Ga

Magnetic state in the quasi-two-dimensional organic conductor λ−(BEST)2FeCl4 and the path of π−dSaito1, Iida2, Kobayashi3 et al. 2022Phys. Rev. BSelf Cite3080View full textAdd to dashboardCite

Antiferromagnetic ordering of organic Mott insulator $λ$-(BEDSe-TTF)$_2$GaCl$_4$

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Magnetic state in the quasi-two-dimensional organic conductor λ−(BEST)2FeCl4 and the path of π−d
Saito
¹
,
Iida
²
,
Kobayashi
³

et al. 2022
Phys. Rev. B
Self Cite
3
0
8
0
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