Spin effects in quasi-one-dimensional conductors under magnetic field

Montambaux, Gilles; Héritier, M.; Lederer, P.

doi:10.1051/jphyslet:019840045011053300

Cited by 34 publications

(11 citation statements)

References 18 publications

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“…the spin-flip part of the short-range electron-electron coupling (gl) can be strongly affected at low temperature (T > 7B) [20,42]. This may also be relevant for the perceptible change in the temperature variation of T compared to low fields.…”

Section: Discussionmentioning

confidence: 99%

Cooperative phenomena in (TMTSF)2ClO4 : an NMR evidence

et al. 1984

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We present 1H and 77Se NMR relaxation data on oriented (TMTSF)2ClO4 single crystals in the relaxed state. The data show the existence of three distinct regimes for the nuclear relaxation rate T-11. In the high temperature part (T > 25 K) the Korringa law seems to be well satisfied whereas in the lower temperature part we have strong deviations down to 8 K or so. At T ≲ 6 K, a different and enhanced Korringa regime appears to be restored. Preliminary results on (TMTSF)2FSO3 under pressure also show similar features. We propose an interpretation of the T-11 behaviour based on the existence of one-dimensional 2 k F spin correlations for repulsive short range intrachain electron-electron interactions. The coherent interchain hopping acts as the main mechanism for the restored but renormalized Korringa behaviour. Moreover, from the low-field data, the proposed scheme of interpretation is not incompatible with the presence of superconducting precursor effects

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Section: Discussionmentioning

confidence: 99%

Cooperative phenomena in (TMTSF)2ClO4 : an NMR evidence

et al. 1984

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“…Therefore the stability of a SDW long range order depends, in principle, on two different factors : 1) the renormalized electron coupling at the cross-over temperature (the ~*(T~)'s in the « g-ology » picture); 2) the details of three-dimensional Fermi surfaces nesting, leading to two different interpretations of the effects of anion ordering and of an applied magnetic field. We have explored the first possibility in a recent paper [13]. Investigating the effect of an applied magnetic field on one-dimensional fluctuations in the g-ology model, we found, indeed, that the SDW stability domain is enlarged by spin effects, but for fields larger than T~o, which seems higher than the experimental threshold fields.…”

Section: Introductionmentioning

confidence: 90%

“…At the same time, Qx and Qy vary so that the surfaces remain tangent while the quantized orbits inflate : quantization of nesting is preserved In this field range, the argument of the Bessel function z ~ n. Eventually, when Qx > 2 kF + 4 tb and 6, = 0 mod 2013 )), the surfaces vu ( ( b* F B B ~ // become separated and z decreases. However, to derive equation (13) we have assumed that the dispersion law could be approximated by equation (3). This becomes invalid at too small values of qx and qy, i.e.…”

Section: T~p And* C*mentioning

confidence: 99%

Stability of the spin density wave phases in (TMTSF)2ClO4 : quantized nesting effect

1984

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2014 La stabilité des phases Onde de Densité de Spin dans (TMTSF)2ClO4 s'interprète par de simples arguments d'ajustement de surfaces de Fermi anisotropes : nous montrons que l'ordre des anions, en introduisant de nouvelles réflexions de Bragg perturbe l'ajustement et abaisse la stabilité de l'Onde de Densité de Spin. Nous améliorons l'argument de Gor'kov et Lebed' sur l'effet d'un champ magnétique sur l'ajustement en permettant au vecteur d'onde Q(H) de s'adapter au champ H, si bien que l'ajustement est quantifié. Nous prévoyons que H induit une succession de phases magnétiques, où Q(H) varie linéairement, séparées par des transitions du premier ordre où Q(H) est discontinu. A basse température, la tension de Hall est constante à l'intérieur d'une phase, comme dans l'Effet Hall Quantifié, en accord avec les données d'effet Hall.

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“…Our two-dimensional model, described in eqs. ( 1)-( 4), can be obtained by a three-cut-off renormalisation group approach [41], in which the three cut-offs are the bandwidth E 0 ≈ 6000 K, the cross-over temperature T co ≈ 100 K and the Zeeman energy µ e H ≈ 2 K, and have different orders of magnitude. In the range where ω < T co , our Fermi liquid analysis is valid.…”

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Magnetic-field–induced singlet-triplet phase transition in quasi–one-dimensional organic superconductors

et al. 2007

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We propose a theoretical model of quasi-one-dimensional superconductors, with attractive electron-electron interactions dominant in the singlet d-wave channel and sub-dominant in the pwave channel. We discuss, in the mean field approximation, the effect of a magnetic field applied perpendicularly to the direction of the lowest conductivity. The lowest free energy phase corresponds to a singlet d-wave symmetry in low fields, but to a triplet symmetry in high fields. A first order singlet-triplet phase transition is expected at moderate applied fields of a few teslas. We propose to ascribe the recent critical field and NMR experimental data, observed in superconducting (T M T SF )2ClO4 to such an effect.PACS numbers: 74.70. Tx, 74.25.Op, 74.20.Rp The nature of superconductivity in the family of the quasi-1D organic superconductors [1, 2, 3] (T M T SF ) 2 X (X = P F 6 , ClO 4 ,...) has been a long standing issue for the last three decades. There is still a debate whether it is a conventional superconductivity, with a completely gapped Fermi surface, or an unconventional one with points or lines of nodes on the gap. Many experiments have tried to address this question using different techniques such as NMR relaxation rate, thermal conductivity, non magnetic impurity effect on T c , Knight Shift and upper critical field measurements.The temperature dependence of the proton spin lattice relaxation rate, measured by Takigawa et al. [6] studied the effect of non magnetic impurities on the superconducting critical temperature T c [7], and showed unequivocally that the order parameter changes sign on the Fermi surface and that consequently the gap has nodes where it is zero on the Fermi surface. This is in complete agreement with a model of unconventional superconductivity in these organic materials.However, whether the pairing of the electrons in the superconducting state is in the singlet or the triplet symmetry remains an unsolved question. Measurements of the upper critical field of superconductivity in these materials [8,9,10] showed a superconducting state surviving up to a field as high as 9 T in the case of the P F 6 compounds [8], and at least 5 T in the case of the ClO 4 compounds [9]. These fields exceed by far the Clogston-Pauli paramagnetic limit [11] for homogeneous singlet superconductivity, which is estimated to be of the order of 1.84 T c , with a T c around 1.1 K in these materials. This result is a strong indication that at high magnetic fields superconductivity could not be of a homogeneous singlet type. Many theories [12,13,14] have been proposed to explain this behaviour by a triplet superconducting state, which is a non Pauli limited state. At low magnetic fields, however, besides the observation by Andres et al.[15] of a diamagnetic signal when the field is perpendicular to the chains indicating a singlet state, measurements of the Knight-Shift [16] showed a significant variation from the normal state behaviour of the spin susceptibility of Cooper pairs which decreased with decreasing temperatur...

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Spin effects in quasi-one-dimensional conductors under magnetic field

Cited by 34 publications

References 18 publications

Cooperative phenomena in (TMTSF)2ClO4 : an NMR evidence

Cooperative phenomena in (TMTSF)2ClO4 : an NMR evidence

Stability of the spin density wave phases in (TMTSF)2ClO4 : quantized nesting effect

Magnetic-field–induced singlet-triplet phase transition in quasi–one-dimensional organic superconductors

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