2D Molecular Superconductor to Insulator Transition in the β′′-(BEDT-TTF)2[(H2O)(NH4)2M(C2O4)3]·18-crown-6 Series (M = Rh, Cr, Ru, Ir)

Morritt, Alexander L.; Lopez, Jordan R.; Blundell, Toby J.; Canadell, Enric; Akutsu, Hiroki; Nakazawa, Yasuhiro; Imajo, Shusaku; Martin, Lee

doi:10.1021/acs.inorgchem.9b00292

Cited by 12 publications

(8 citation statements)

References 35 publications

(70 reference statements)

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“…In Fig. 8, we present the plot of m * and the SdH frequency F of β ′′ -(BEDT-TTF) 2 SF 5 CH 2 CF 2 SO 3 (T c : ∼5.2 K, m * : ∼1.9m e , F : ∼200 T) [35] and [36,37] with the results of the present salts. It is clearly found that the parameters of the two salts fall in the correlation derived from our results.…”

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confidence: 55%

Effects of electron correlations and chemical pressures on superconductivity of β′′ -type organic compounds

Imajo

Akutsu

Akutsu-Sato

et al. 2019

Phys. Rev. Research

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We investigate low-temperature electronic states of the series of organic conductors β ′′ -(BEDT-TTF)4[(H3O)M(C2O4)3]G, where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene, and M and G represent trivalent metal ions and guest organic molecules, respectively. Our structural analyses reveal that the replacement of M and G give rise to systematic change in the cell parameters, especially in the b-axis length, which has positive correlation with the superconducting transition temperature Tc. Analyses of temperature and magnetic field dependences of the electrical resistance including the Shubnikov-de Haas oscillations elucidates that the variation of charge disproportionation, effective mass and the number of itinerant carriers, can be systematically explained by the change of the b-axis length. The changes of the transfer integrals induced by stretching/compressing the b-axis are confirmed by the band calculation. We discuss that electron correlations in quarter-filled electronic bands lead to charge disproportionation and the possibility of a novel pairing mechanism of superconductivity mediated by charge degrees of freedom.Superconductivity dominated by electron correlations often appears in nearly half-filled electronic bands, where an antiferromagnetic Mott insulating state is easily formed by on-site Coulomb repulsion U . In such cases, the superconductive regions are located in close proximity to the magnetic Mott phases in electronic phase diagrams [1][2][3]. Therefore, unconventional pairing related to magnetic spin fluctuations has been suggested to provide an understanding of the mechanisms of the superconductivity. Indeed, highest critical temperatures T c are normally observed on the verge of the magnetic phases because the quantum fluctuation coming from the spin degree of freedom is strongly enhanced. High-T c cuprates[1], heavy fermion superconductors[2] and dimer-Mott type organic superconductors [3] have been discussed as such candidates of spin-fluctuation-mediated superconductors. Other degrees of freedom, such as orbital (multipole) [4,5] and charge [6], have been also proposed as origins of the pairing in some superconductors, e.g. iron-based compounds, cage compound, etc. However, it is difficult to examine the relationship between the quantum degrees of freedom and superconductivity because the number of such exotic superconductors is rather small and the pairing states are often in complicated situations due to the coexistence/competition of some degrees of freedom.Recently, β ′′ -type organic charge-transfer salts consisting of BEDT-TTF molecules with counter anions and guest solvent molecules have drawn extensive attention because they are expected to have a novel Cooper pairing mechanism related to charge degrees of freedom [6][7][8][9][10][11][12][13][14][15]. The critical temperatures T c of some β ′′ -salts are relatively high around 7-8 K, which is almost com-parable to the T c of well-known higher-T c dimer-Mott organic superconductors, κ-(BEDT-TTF) 2 X. Also, the strong-coupling ...

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confidence: 55%

Effects of electron correlations and chemical pressures on superconductivity of β′′ -type organic compounds

Imajo

Akutsu

Akutsu-Sato

et al. 2019

Phys. Rev. Research

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“…We recently published a 2 : 1 salt, b 00 -(BEDT-TTF) 2 [(H 2 O)(NH 4 ) 2 Ir(C 2 O 4 ) 3 ]Á18-crown-6, which was the first example in this family to contain a 5d tris(oxalato)metallate anion. 18 A 4 : 1 BEDT-TTF salt has previously been reported with 5d bis(oxalato)platinate, Pt(C 2 O 4 ) 2 2À , which shows metallic behaviour down to 60 K. 26 When using benzonitrile with tris(oxalato)iridate in salt 5 we have also used halobenzenes with tris(oxalato)iridate but no crystals could be obtained, in contrast to the relative ease with which they can be obtained when using the 3d and 4d tris(oxalato)metallates.…”

Section: Materials Advances Papermentioning

confidence: 99%

Molecular conductors from bis(ethylenedithio)tetrathiafulvalene with tris(oxalato)gallate and tris(oxalato)iridate

Blundell,

Morritt,

Rusbridge

et al. 2022

Mater. Adv.

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“…Interestingly, both salts are metallic at room temperature but show metalinsulator transitions at 190 and 240 K, respectively. [36], Ru (66) [36], Cr (67) [37] and Rh (69) [38] (Table 3). The structure resembles that of the previously described compounds β"-(ET) The Cr and Rh salts are superconductors with T c = 4.0-4.9 K and 2.7 K, respectively [37,38].…”

Section: Other Phases With Bedt-ttf and Oxalato Complexesmentioning

confidence: 99%

“…The Ir and Ru salts are not superconductors due to the shorter inter-layer M-M distance (worse 2D systems). The M-I transition in these salts may originate from changes in the anionic layer which induce changes in the BEDT-TTF layer, although Berezinski-Kosterlitz-Thouless (BKT) effects are not discarded [36]. The Ir salt is the first radical salt with a 5d tris(oxalato)metalate anion [36].…”

Section: Other Phases With Bedt-ttf and Oxalato Complexesmentioning

confidence: 99%

“…H atoms are omitted for clarity. A second phase obtained with 18-crown-6 is the series of salts formulated as β"-(ET) 2 [(H 2 O)(NH 4 ) 2 M(C 2 O 4 ) 3 ]•18-crown-6, with M = Ir (65)[36], Ru (66)[36], Cr (67)[37] and Rh (69)[38] (Table3). The structure resembles that of the previously described compounds β"-(ET)4 [(A)M(C 2 O 4 ) 3 ] 2 [(A) 2 (18-crown-6)]•5H 2 O with A + /M = H 3 O + /Cr (64) and NH 4 + /Ga (68).…”

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The Peter Day Series of Magnetic (Super)Conductors

Benmansour

Gómez‐García

2021

Magnetochemistry

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Here, we review the different series of (super)conducting and magnetic radical salts prepared with organic donors of the tetrathiafulvalene (TTF) family and oxalato-based metal complexes (ox = oxalate = C2O42−). Although most of these radical salts have been prepared with the donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF = ET), we also include all the salts prepared with other TTF-type donors such as tetrathiafulvalene (TTF), tetramethyl-tetrathiafulvalene (TM-TTF), bis(ethylenediseleno)tetrathiafulvalene (BEST), bis(ethylenedithio)tetraselenafulvalene (BETS) and 4,5bis((2S)-2-hydroxypropylthio)-4’,5’-(ethylenedithio)tetrathiafulvalene (DMPET). Most of the oxalate-based complexes are monomers of the type [MIII(C2O4)3]3−, [Ge(C2O4)3]2− or [Cu(C2O4)2]2−, but we also include the reported salts with [Fe2(C2O4)5]4− dimers, [MII(H2O)2[MIII(C2O4)3]2]4− trimers and homo- or heterometallic extended 2D layers such as [MIIMIII(C2O4)3]− and [MII2(C2O4)3]2−. We will present the different structural families and their magnetic properties (such as diamagnetism, paramagnetism, antiferromagnetism, ferromagnetism and even long-range magnetic ordering) that coexist with interesting electrical properties (such as semiconductivity, metallic conductivity and even superconductivity). We will focus on the electrical and magnetic properties of the so-called Day series formulated as β”-(BEDT-TTF)4[A+MIII(C2O4)3]·G, which represents the largest family of paramagnetic metals and superconductors reported to date, with more than fifty reported examples.

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2D Molecular Superconductor to Insulator Transition in the β′′-(BEDT-TTF)₂[(H₂O)(NH₄)₂M(C₂O₄)₃]·18-crown-6 Series (M = Rh, Cr, Ru, Ir)

Cited by 12 publications

References 35 publications

Effects of electron correlations and chemical pressures on superconductivity of β′′ -type organic compounds

Effects of electron correlations and chemical pressures on superconductivity of β′′ -type organic compounds

Molecular conductors from bis(ethylenedithio)tetrathiafulvalene with tris(oxalato)gallate and tris(oxalato)iridate

The Peter Day Series of Magnetic (Super)Conductors

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