New SDW phases in quasi-one-dimensional systems dimerized in the transverse direction

Zanchi, D.; Bjeliš, Aleksa

doi:10.1209/epl/i2001-00562-1

Cited by 16 publications

(33 citation statements)

References 17 publications

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“…As shown above the method enables a practically unambiguous fit of rapid oscillations observed in various physical properties in the metallic as well as in FISDW state. It leads to the additional evidence in favor of expectations that the anion potential V is of the order of the transverse bandwidth t. This is in accordance with the analysis of SDW [6,7] and FISDW [8] phase diagram for (TMTSF) 2 ClO 4 . Finally we note that the present method can be straightforwardly generalized to richer and more complex geometries and physical situations.…”

Section: Resultssupporting

confidence: 86%

Exact solution of the magnetic breakdown problem in quasi-one-dimensional geometry

Radić¹,

Bjeliš²,

Zanchi³

2004

J. Phys. IV France

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Abstract. We present exact solution of the problem of electronic wave functions of quasi one-dimensional band with an inter-band gap at the Fermi surface and in the presence of magnetic field. The details of the analyzed model are appropriate to the situation in the Bechgaard salt (TMTSF) 2 ClO 4 with the dimerizing anion order in the transverse direction. Limiting the effects of dimerization to the standard dimerization gap only, one obtains the electronic spectrum represented through solutions of a generalized Hill system of equations with simply periodic coefficients. The resulting wave-functions are discussed. In particular, we present the solutions for the case when the electrons spend as much time in the "junctions" as on their quasi-classical orbits. On the other hand, the limit when the tunnelling approach is valid is identified and the results are confronted with the well-known Slutskin-Kadigrobov solution. Furthermore, taking into account also the presumably finite transverse dimerizing displacements of chains, one encounters the qualitatively more complex problem of a system of equations with two-periodic coefficients. Some qualitatively new properties of electronic spectrum and corresponding one-electron physical quantities in this case will be discussed in detail.Key words. anion gap, magnetic breakdown MOTIVATIONThe field-induced spin density wave (FISDW) state and other physical properties of Bechgaard salts with one open Fermi surface are interpreted by the well-known concept of one-dimensionalization of open electron orbits in the plane perpendicular to the external magnetic field B [1]. However, in slowly cooled samples of (TMTSF) 2 ClO 4 with the orientational anion ordering the Brillouin zone is reduced due to a finite dimerization potential along the b-axis perpendicular to the chain direction, and the electron spectrum is split into two sub-bands. Then one encounters the problem of magnetic breakdown of quasi-classical electron orbits through the barrier separating two Fermi surfaces. In the standard treatment [2,3] of this problem one constructs new electron states by including only the local tunnelling through the barrier at the Brillouin zone edges (transverse wave number close to π /2b). This approach is justified provided that the magnetic breakdown parameter κ ≡ ω c t/V 2 is (much) larger than unity [4]. Here V is the potential generated by the anion ordering, t is transverse hopping integral, and ω c ≡ v F eBb/ћ is cyclotron frequency.For κ >>1 one has strong magnetic breakdown, i. e. the tunnelling probability exp (-1/κ) is large. Evidently this regime is possible only if V is weak with respect to t. However recent experimental [5] and theoretic [6,7] results suggest that V might be of the order or larger than t. In this case one cannot use the standard method of Refs. [2][3][4]. We introduce in the present paper an alternative exact approach, generally applicable to the problem of magnetic breakdown. EXACT APPROACHWe start from the basic one-electron Hamiltonian with the Peierls su...

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Section: Resultssupporting

confidence: 86%

Exact solution of the magnetic breakdown problem in quasi-one-dimensional geometry

Radić¹,

Bjeliš²,

Zanchi³

2004

J. Phys. IV France

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“…6͑a͒ is stabilized for a large V. 17 In fact, the magnitude of V estimated from the angular dependent magnetoresistance measurements is of the order of the interchain hopping integral t b . 18 Recent calculations for ClO 4 salt have pointed out that, when V is increased, the SDW state with Q SDW is rapidly suppressed while the SDW state with Q SDW Ϯ becomes stable at higher value of V. 19,20 Because the FISDW phase between 12 and 24 T is suppressed with increasing R C , it is reasonable to estimate that the respective ground states of the last semimetallic FISDW phase and of the insulating FISDW phase are a nϭ1 state with Q SDW Ϯ and a n ϭ0 insulating state with Q SDW . Because the FISDW phase with Q SDW Ϯ becomes more stable with increasing the value of V, the model with Q SDW Ϯ can explain the decrease of ␤ HI and the suppression of the last semimetallic SDW phase.…”

Section: Resultsmentioning

confidence: 99%

Role of the dimerized gap due to anion ordering in spin-density wave phase of(TMTSF)2ClO4at hi

Matsunaga¹,

Ayari²,

Monçeau³

et al. 2002

Phys. Rev. B

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Magnetoresistance measurements have been carried out along the highly conducting a axis in the fieldinduced spin-density wave ͑FISDW͒ phase of hydrogenated and deuterated (TMTSF) 2 ClO 4 for various cooling rates through the anion ordering temperature. With increasing the cooling rate, ͑i͒ the high-field phase boundary ␤ HI , observed at 27 T in hydrogenated samples for slowly cooled, is shifted towards a lower field, ͑ii͒ the last semimetallic SDW phase below ␤ HI is suppressed, and ͑iii͒ the FISDW insulating phase above ␤ HI is enhanced in both salts. The cooling rate dependence of the FISDW transition and of ␤ HI in both salts can be explained by taking into account the peculiar SDW nesting vector stabilized by the dimerized gap due to anion ordering.

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“…The concomittant reduction of the Brillouin zone yields two electronic bands at the Fermi level and in turn multiple nesting vectors. 81,82 An accurate description of this Fermi surface should be incorporated in the RG approach, and a modification of the node structure for the SC gap is expected. 83 A previous ͑simplified͒ RPA-like calculation has shown that the nodes of a d-wave SC order parameter, which are located at k Ќ = ± / 2, are precisely found where a gap opens due to ClO 4 anion ordering, thus making the SC phase effectively nodeless at low temperature.…”

Section: Discussionmentioning

confidence: 99%

Superconducting pairing and density-wave instabilities in quasi-one-dimensional conductors

et al. 2006

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Using a renormalization group approach, we determine the phase diagram of an extended quasi-onedimensional electron gas model that includes interchain hopping, nesting deviations, and both intrachain and interchain repulsive interactions. d-wave superconductivity, which dominates over the spin-density-wave ͑SDW͒ phase at large nesting deviations, becomes unstable to the benefit of a triplet f-wave phase for a weak repulsive interchain backscattering term g 1 Ќ Ͼ 0, despite the persistence of dominant SDW correlations in the normal state. Antiferromagnetism becomes unstable against the formation of a charge-density-wave state when g 1 Ќ exceeds some critical value. While these features persist when both Umklapp processes and interchain forward scattering ͑g 2 Ќ ͒ are taken into account, the effect of g 2 Ќ alone is found to frustrate nearest-neighborinterchain d-and f-wave pairing and instead favor next-nearest-neighbor interchain singlet or triplet pairing. We argue that the close proximity of SDW and charge-density-wave phases, singlet d-wave, and triplet f-wave superconducting phases in the theoretical phase diagram provides a possible explanation for recent puzzling experimental findings in the Bechgaard salts, including the coexistence of SDW and charge-density-wave phases and the possibility of a triplet pairing in the superconducting phase.

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New SDW phases in quasi-one-dimensional systems dimerized in the transverse direction

Cited by 16 publications

References 17 publications

Exact solution of the magnetic breakdown problem in quasi-one-dimensional geometry

Exact solution of the magnetic breakdown problem in quasi-one-dimensional geometry

Role of the dimerized gap due to anion ordering in spin-density wave phase of(TMTSF)2ClO4at hi

Superconducting pairing and density-wave instabilities in quasi-one-dimensional conductors

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