K BEDT-TTF

An initial attempt was made to correlate the structural properties of the kl-(BEDT-TTF)2M(CF3)4(TCE) salts with their superconducting transition temperature [31]. The relationship between Tc and any single unit cell parameter failed to show any discemable trend. The best correlation was obtained by plotting Tc as a function of the b/c ratio, where b is the interlayer and c is an intralayer direction. A similar conclusion was reached through the determination of uniaxial pressure coefficients of p -(BEDT-TTF)2SF5CH2CF2S03 and k-(BEDT-TTF)2Cu(NCS)2 through the measurement of thermal expansion [32]. These results also indicated that expansion of the interlayer direction and compression of an intralayer direction... 

The effect of deuterium isotope substitution on Tc has been studied for three members of the KL-(BEDT-TTF)2Ag(CF3)4(l,l,2-trihaloethane) family [12, 34-36]. In all cases, the Tc increased upon deuteration with the effect ranging from 0.21 to 0.36 K. These results are similar to the deuterium isotope effect observed in the p"-(BEDT-TTF)2SF5CH2CF2S03 [34, 37] and k-(BEDT-TTF)2Cu(NCS)2 [38] superconductors. 

The band electronic structure of kl-(BEDT-TTF)2Cu(CF3)4(TCE) was calculated through the use of Hiickel tight binding computations [39] and the infrared properties analyzed [40]. These calculations indicate that the electronic band structure [10, 41] and infrared response [42] is similar to that found in the k-(BEDT-TTF)2Cu(dca)X (X = Cl and Br) salts. Specific heat measurements of kl-(BEDT-TTF)2Ag(CF3)4(TCE) indicate a linear coefficient (y = 50 mJ mol 1 K2), which is a factor of nine greater than expected from a free-electron picture [43],... 

Miyagawa K, Kawamoto K, Nakazawa Y, Kanoda K (1995) Antiferromagnetic ordering and spin structure in the organic conductor, k-(BEDT-TTF)2Cu[N(CN)2]C1. Phys Rev Lett 75 1174-1177... 

Posselt H, Muller H, Andres K, Saito G (1994) Reentrant Meissner effect in the organic conductor k-(BEDT-TTF)2Cu[N(CN)2]C1 under pressure. Phys Rev B49 15849-15852... 

Sushko YV, Ito H, Ishiguro T, Horiuchi S, Saito G (1993) Magnetic-field-induced transition to resistive phase in superconducting k-(BEDT-TTF)2Cu[N(CN)2]C1. J Phys Soc Jpn 62 3372-3375... 

Ito H, Kubota M, Ishiguro T, Saito G (1997) Metal-nonmetal transition of hydrogenated and deuterated k-(BEDT-TTF)2Cu[N(CN)2]X under pressure. Synth Met 85 1517-1518... 

Kobayashi A, Kato R, Kobayashi H, Moriyama S, Nishio Y, Kajita K, Sasaki W (1987) Crystal and electronic structures of a new molecular superconductor, K-(BEDT-TTF)2l3. Chem Lett 16 459 62... 

Kino H, Fukuyama H (1995) Electronic states of conducting organic k-(BEDT-TTF)2X. J Phys Soc Jpn 64 2726-2729... 

Ohira S, Shimizu Y, Kanoda K, Saito G (2006) Spin liquid state in k-(BEDT-TTF)2Cu2(CN)3 studied by muon spin relaxation method. J Low Temp Phys 142 153-158... 

Yamashita M, Nakata N, Kasahara Y, Sasaki T, Yoneyama N, Kobayashi N, Fujimoto S, Shibauchi T, Matsuda Y (2009) Thermal-transport measurements in a quantum spin-liquid state of the frustrated triangular magnet k-(BEDT-TTF)2Cu2(CN)3. Nat Phys 5 44-47... 

Maesato M, Shimizu Y, Ishikawa T, Saito G (2003) Anisotropy in the superconducting transition temperature of k-(BEDT-TTF)2X. Synth Met 137 1243-1244... 

Komatsu T, Matsukawa N, Inoue T, Saito G (1996) Realization of superconductivity at ambient pressure by band-filling control in k-(BEDT-TTF)2Cu2(CN)3. J Phys Soc Jpn 65 1340-1354... 

Komatsu T, Kojima N, Saito G (1997) Ambient-pressure superconductivity of k -(BEDT-TTF)2Cu2(CN)3 realized by a carrier-doping into a Mott-insulating state. Synth Met 85 1519-1520... 

It is interesting to compare the temperature dependence of the amplitude for all frequencies (see Fig. 6 for T = 1.5 K and Fig. 7 T = 4.2 K). At 1.5 K the a and (P-a) oscillation amplitudes dominate whereas the (P-2a) amplitude oscillation is very small. However, the (P-2a) amplitude oscillation dominates and the P one disappears completely at 4.2 K. These results are in agreement with the effective mass values corresponding to these oscillation frequencies and satisfy the necessary relations between effective masses for the QI effect. Noting that below 4.2 K the oscillation amplitude connected with the (P-2a) frequency is constant within the experimental error (i.e., a zero cyclotron mass), we may assume that this oscillation can survive to considerably higher temperatures. An analogous situation has been previously found for the (k-BEDT-TTF)2Cu(NCS)2 salt [13],... 

Kartsovnik M.V., Logvenov G.Yu., Ishiguro T., Biberacher W.., Anzai H. and Kushch. (1996) Direct Oscillation of the Magnetic-Breakdown Induced Quantum Interference in Quasi-Two-Dimensional Organic Metal k-(BEDT-TTF)2Cu (SCN)2 Phys. Rev. Lett. 77, 2530-2533. 

So far all TMTSF and almost all ET-type superconductors have mixed valence and p=. The TMTSF salts and some ET salts are quasi-ID, but with enough warping of the Fermi surface to make them pseudo-2D and to defeat the Peierls transition. The k-phase (BEDT-TTF) salts are really 2-D systems this phase, shown in Fig. 12.7, has isolated dimers connected by dispersion interactions to form, roughly, two-dimensional sheets. Figure 12.8 shows the superconductivity of the salt k-(BEDT-TTF)2Cu(NCS)2 at 10.4 K [34]. 

P2x/c. The absence of a superconductivity transition in some samples of the latter material is attributed to twinning. Twinning in k-(BEDT-TTF)2(Cu)NCS)2 is described by Watanabe et al. [172],... 

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