A new ambient-pressure organic superconductor, .kappa.-(ET)2Cu[N(CN)2]Br, with the highest transition temperature yet observed (inductive onset Tc = 11.6 K, resistive onset = 12.5 K)

Kini, A. M.; Geiser, U.; Wang, Hau H.; Carlson, K. Douglas; Williams, Jack M.; Kwok, W. K.; Vandervoort, K. G.; Thompson, James E.; Stupka, D. L.

doi:10.1021/ic00339a004

Cited by 631 publications

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“…Figure 6 shows the 20 K spectra of all of the compounds investigated in this study. These are arranged in order of increasing T, proceeding from the bottom to the top of the figure, with the three K-phase compounds on Table 4 Unit ceil parameters and the superconducting transition temperatures of the (ET)zX salts investigated in this study [4]. ') Ref.…”

Section: Cu(ncs)ymentioning

confidence: 99%

The correlation of lattice phonon frequencies with the superconducting transition temperatures of some (BEDT-TTF) salts

Dressel

Eldridge

Williams

et al. 1992

Physica C: Superconductivity

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The far-infrared powder absorption spectra, between 10 cm-' and 350 cm-', of seven BEDT-TTF salts that exhibit superconductivity at or near ambient pressure, have been measured as a function of temperature, between 5 K and 300 K. The temperature dependences of the peak frequencies, along with the measured deuterium isotopic frequency shifts, separated the lattice from the internal modes. The frequencies of the observed lattice modes were found to increase with T, in the three K-phase salts in agreement with the reduced volume of the unit cell, and to have a mixed response in the three B-phase compounds. Furthermore, the genera1 range and magnitude of the frequencies in the higher-T, K-phase compounds were found to be larger than in the lower T, pphase compounds. Consequently, no evidence was found for a correlation between higher values of T, and a softer lattice in these organic superconductors.

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Section: Cu(ncs)ymentioning

confidence: 99%

The correlation of lattice phonon frequencies with the superconducting transition temperatures of some (BEDT-TTF) salts

Dressel

Eldridge

Williams

et al. 1992

Physica C: Superconductivity

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“…The electronic band is effectively half filled and the system is on the insulating side of a nearby metal-insulator Mott transition. The two chemically equivalent organic ET layers [10,11], A and B (Fig. 1) are separated by Cu[N(CN) 2 ]Cl polymer sheets.…”

mentioning

confidence: 99%

Magnetic fluctuations above the Néel temperature in κ‐(BEDT‐TTF)₂Cu[N(CN)₂]Cl, a quasi‐2D Heisenberg antiferromagnet with Dzyaloshinskii–Moriya interaction

Antal

Fehér

Náfrádi

et al. 2012

Physica Status Solidi (b)

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Field-induced antiferromagnetic (AF) fluctuations and magnetization are observed above the (zero-field) ordering temperature, TN = 23 K by electron spin resonance in κ-(BEDT-TTF)2Cu[N(CN)2]Cl, a quasi two-dimensional antiferromagnet with a large isotropic Heisenberg exchange interaction. The Dzyaloshinskii-Moriya (DM) interaction is the main source of anisotropy, the exchange anisotropy and the interlayer coupling are very weak. The AF magnetization is induced by magnetic fields perpendicular to the DM vector; parallel fields have no effect. The different orientation of the DM vectors and the g factor tensors in adjacent layers allows the distinction between interlayer and intralayer correlations. Magnetic fields induce the AF magnetization independently in adjacent layers. We suggest that the phase transition temperature, TN is determined by intralayer interactions alone.PACS numbers: 76.30.-v, 76.50+g, 75.30-m One-dimensional (1D) magnets, i.e., isolated chains of magnetic atoms or molecules have no ordering phase transitions while 3D magnets order at finite temperatures, T N . Magnetic ordering in two dimensions, i.e., in isolated planes, is a delicate question [1]. Theory predicts for most anisotropic two-dimensional (2D) magnets a phase transition at finite T N except if ordering breaks a continuous symmetry. The case of S = 1/2 anisotropic Heisenberg antiferromagnets is complicated [2]. Experiments on low dimensional magnets with negligible interactions between the magnetic chains or planes are rare. The magnetic-field-induced change in the excitation spectrum of 1D Heisenberg chains [3,4] agrees with theory [5,6]. Field-induced magnetism has also been studied in a quasi 2D S = 1 dimer system [7]. The present experiments are on a quasi 2D, S = 1/2 magnet where the continuous symmetry is broken by a very small anisotropy and the applied magnetic field, H.is a layered spin 1/2 Heisenberg antiferromagnet with a magnetic ordering transition [8] at T N = 23 K measured [9] in H = 0. The ET molecules are arranged in a 2D lattice of singly charged dimers. The electronic band is effectively half filled and the system is on the insulating side of a nearby metal-insulator Mott transition. The two chemically equivalent organic ET layers [10, 11], A and B (Fig. 1) are separated by Cu[N(CN) 2 ]Cl polymer sheets.The ordered state is well described by two-sublattice antiferromagnetic layers weakly coupled through the polymeric sheets [12]. The measured macroscopic parameter of the in-plane isotropic exchange, (J/2) i,j S i · S j is λM 0 = 2J/(gµ B ) = 450 T [8,13]. The magnitude of the antisymmetric Dzyaloshinskii-Moriya (DM) ex- Kagawa et al. [9] pointed out that in κ-ET 2 -Cl the DM interaction plays an important role above T N . In magnetic fields (unless parallel to the DM vector) the phase transition is replaced by a crossover. In this case the AF magnetization remains finite above T N and there is a weak ferromagnetic moment along H at all temperatures. They measured µ s , the field-induced staggered static magne...

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“…Details of the growth procedures have been given elsewhere [14]. Penetration depth measurements were performed using a 13 MHz tunnel diode oscillator [15] mounted on a 3 He refrigerator.…”

mentioning

confidence: 99%

Low-Temperature Penetration Depth ofκ−(ET)2Cu[N(CN)2
Carrington
¹
,
Bonalde
²
,
Prozorov
³

et al. 1999
Phys. Rev. Lett.
145
19
122
0
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We present high precision measurements of the penetration depth of single crystals of κ−(ET)2Cu[N(CN)2]Br and κ−(ET)2Cu(NCS)2 at temperatures down to 0.4 K. We find that, at low temperatures, the in-plane penetration depth (λ ) varies as a fractional power law, λ ∼ T 3 2 . Whilst this may be taken as evidence for novel pair excitation processes, we show that the data are also consistent with a quasilinear variation of the superfluid density, as is expected for a d-wave superconductor with impurities or a small residual gap. Our data for the interplane penetration depth show similar features and give a direct measurement of the absolute value, λ ⊥ (0) = 100 ± 20 µm.PACS numbers: 74.70. Kn, 74.25.Nf Compounds of the family κ−(ET) 2 X have the highest transition temperatures of all organic superconductors known to date [1]. They have recently attracted considerable attention because of their similarity to the high T c cuprates and the possibility that they may also have a non-conventional paring state [2]. The two materials studied here, κ−(ET) 2 Cu[N(CN) 2 ]Br (T c ∼ 11.6 K) and κ−(ET) 2 Cu(NCS) 2 (T c ∼ 9.6 K), are highly anisotropic, layered, extreme type II superconductors. As in the cuprates, the superconducting phase in these materials is in close proximity to an antiferromagnetic phase. Both antiferromagnetic spin fluctuations and a pseudogap have been detected in NMR measurements in the normal state [3]. Neither the underlying pairing mechanism nor the symmetry of the order parameter has been conclusively established. Although NMR [4,5], specific heat [6] and thermal conductivity [7] measurements all suggest a non-conventional pairing state, results of penetration depth measurements have been inconsistent, with evidence for both conventional [8,9] and non-conventional [10][11][12] behavior. However, none of these penetration depth measurements have been performed over a temperature range (T /T c ) and a precision, comparable to those in the cuprates [13]. In this Letter, we present measurements of both the in-plane λ , and the interplane, λ ⊥ , penetration depths in κ−(ET) 2 Cu[N(CN) 2 ]Br and κ−(ET) 2 Cu(NCS) 2 at temperatures down to 0.4 K.Our measurements were performed on single crystals of κ−(ET) 2 Cu[N(CN) 2 ]Br and κ−(ET) 2 Cu(NCS) 2 which were grown at Argonne National Laboratory. Details of the growth procedures have been given elsewhere [14]. Penetration depth measurements were performed using a 13 MHz tunnel diode oscillator [15] mounted on a 3 He refrigerator. The low noise level [ ∆F F0 ≃ 10 −9 ], and low drift of the oscillator allows us to obtain high resolution data with a very small temperature spacing interval. The samples were attached, with a small amount of vacuum grease, to a sapphire rod which fitted inside the copper sense coil. The sense coil was calibrated using spheres of Aluminum. The sample temperature was measured with a calibrated Cernox thermometer attached to the other end of the sapphire rod. The samples were cooled slowly (0.1-1.0 K/min) to avoid introducing disorder [1...

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A new ambient-pressure organic superconductor, .kappa.-(ET)2Cu[N(CN)2]Br, with the highest transition temperature yet observed (inductive onset Tc = 11.6 K, resistive onset = 12.5 K)

Cited by 631 publications

References 1 publication

The correlation of lattice phonon frequencies with the superconducting transition temperatures of some (BEDT-TTF) salts

The correlation of lattice phonon frequencies with the superconducting transition temperatures of some (BEDT-TTF) salts

Magnetic fluctuations above the Néel temperature in κ‐(BEDT‐TTF)₂Cu[N(CN)₂]Cl, a quasi‐2D Heisenberg antiferromagnet with Dzyaloshinskii–Moriya interaction

Low-Temperature Penetration Depth ofκ−(ET)2Cu[N(CN)2
Carrington
¹
,
Bonalde
²
,
Prozorov
³

et al. 1999
Phys. Rev. Lett.
145
19
122
0
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A new ambient-pressure organic superconductor, .kappa.-(ET)2Cu[N(CN)2]Br, with the highest transition temperature yet observed (inductive onset Tc = 11.6 K, resistive onset = 12.5 K)

Cited by 631 publications

References 1 publication

The correlation of lattice phonon frequencies with the superconducting transition temperatures of some (BEDT-TTF) salts

The correlation of lattice phonon frequencies with the superconducting transition temperatures of some (BEDT-TTF) salts

Magnetic fluctuations above the Néel temperature in κ‐(BEDT‐TTF)2Cu[N(CN)2]Cl, a quasi‐2D Heisenberg antiferromagnet with Dzyaloshinskii–Moriya interaction

Low-Temperature Penetration Depth ofκ−(ET)2Cu[N(CN)2Carrington1, Bonalde2, Prozorov3 et al. 1999Phys. Rev. Lett.145191220View full textAdd to dashboardCite

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Magnetic fluctuations above the Néel temperature in κ‐(BEDT‐TTF)₂Cu[N(CN)₂]Cl, a quasi‐2D Heisenberg antiferromagnet with Dzyaloshinskii–Moriya interaction

Low-Temperature Penetration Depth ofκ−(ET)2Cu[N(CN)2
Carrington
¹
,
Bonalde
²
,
Prozorov
³

et al. 1999
Phys. Rev. Lett.
145
19
122
0
View full text Add to dashboard Cite