Specific heat at CDW transitions in bronzes

Chung, Max; Kuo, Y. K.; Mozurkewich, George; Figueroa, E.; Teweldemedhin, Z.S.; Carlo, D. A. Di; Greenblatt, Martha; Brill, J. W.

doi:10.1051/jp4:1993249

Cited by 9 publications

(9 citation statements)

References 4 publications

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“…However, Mozurkevich has argued that the Gaussian approximation is not valid in this temperature range 57 . Chung et al 58 found that dχ/dT was comparable to C P when a background contribution was subtracted from the latter. Brill et al 5 found that χ was proportional to the entropy (evaluated from integrating the specific heat) between 140 and 220 K. (This is equivalent to a scaling between dχ/dT and C P ).…”

Section: E Chandra's Scaling Relationmentioning

confidence: 97%

Microscopic theory of the pseudogap and Peierls transition in quasi-one-dimensional materials

McKenzie

1995

Phys. Rev. B

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The problem of deriving from microscopic theory a Ginzburg-Landau free energy functional to describe the Peierls or charge-density-wave transition in quasi-one-dimensional materials is considered. Particular attention is given to how the thermal lattice motion affects the electronic states. Near the transition temperature the thermal lattice motion produces a pseudogap in the density of states at the Fermi level. Perturbation theory diverges and the traditional quasi-particle or Fermi liquid picture breaks down. The pseudogap causes a significant modification of the coefficients in the Ginzburg-Landau functional from their values in the rigid lattice approximation, which neglects the effect of the thermal lattice motion.which is a measure of the fluctuations along a single chain. It was assumed that the coefficients a, b, and c were independent of temperature and the measurable quantities at the transition were determined as a function of the interchain coupling. The transition temperature increases as the interchain coupling increases. The coherence length and specific heat jump depends only on the single chain coherence length, ξ 0 ≡ (c/|a|) 1/2 , and the interchain coupling. The width of the critical region, estimated from the Ginzburg criterion, was virtually parameter independent, being about 5-8 per cent of the transition temperature for a tetragonal crystal. Such a narrow critical region is consistent with experiment, and shows that Ginzburg-Landau theory should be valid over a broad temperature range.This paper uses a simple model to demonstrate some of the difficulties involved in deriving the coefficients a, b, c, and J from a realistic microscopic theory. C. Microscopic theoryThe basic physics of quasi-one-dimensional CDW materials is believed to be described by a Hamiltonian due to Fröhlich 13 which describes electrons with a linear coupling to phonons. Even in one dimension this is a highly non-trivial many-body system and must treated by some approximation scheme. The simplest treatment 13-15 is a Hence, the temperature dependence is quite different from the dependence κ ∼ T 2 that was assumed in References 10,35,36 and the analysis there needs to be modified. The second and more serious problem is one of self-consistency. The coefficients a, b, and c are calculated neglecting fluctuations in the order parameter which will modify the electronic properties which in turn will modify the coefficients. In this paper a simple model is used to demonstrate that the fluctuations have a significant effect on the single-chain coefficients.An alternative microscopic theory, due to Schulz 16 , and which takes into account fluctuations in only the phase of the order parameter is briefly reviewed in Appendix A. D. OverviewDiscrepancies between phonon rigid-lattice theory and the observed properties of the Peierls state well below the transition temperature T P were recently resolved 31,32 by taking into account the effect of the zero-point and thermal lattice motion on the electronic properties. It was shown that...

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Section: E Chandra's Scaling Relationmentioning

confidence: 97%

Microscopic theory of the pseudogap and Peierls transition in quasi-one-dimensional materials

McKenzie

1995

Phys. Rev. B

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“…DC p is the molar specific heat change at the transition temperature T c : p is the number of d conduction electrons per formula unit in the high temperature phase, calculated from the chemical formula phase from the chemical formula. First, it is clear that the 'doped' compounds K x P 4 W 8 O 32 show larger anomalies than the 'pure' one, P 4 W 8 O 32 , which is a 'well-established' CDW material [11]. It is also interesting to compare these results with those obtained on the Mo oxides and bronzes, which are canonical CDW materials.…”

Section: Discussionmentioning

confidence: 88%

“…One may also compare these thermal data to the predictions of mean-field theory for the Peierls transition. The change of specific heat at the transition is in this model related to the change of the electronic density of states at the Fermi level, Dgð1 F Þ; through: DC p =RT c ¼ 4:7 Dgð1 F Þk B ; where k B is the Boltzmann constant [11]. Such an analysis would give in the case of K x P 4 W 8 O 32 unphysical values for Dgð1 F Þ in the range of 20 -40 eV 21 mol 21 .…”

Section: Discussionmentioning

confidence: 99%

“…Previous low temperature measurements on P 4 W 8 O 32 have shown that the Debye temperature of this compound is in the range of 280 K [10]. Other measurements at higher temperatures could not detect the CDW transitions, this indicating that the thermal anomalies are smaller than 0.5% of the specific heat value in the 'pure' compound [11]. In the case of K x P 4 W 8 O 32 , the Debye temperature has been found to be 350^10 K for the three compounds studied with x values of 1.07, 1.25 and 1.6 [6].…”

Section: Introductionmentioning

confidence: 85%

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Specific heat anomalies in the quasi two-dimensional monophosphate tungsten bronzes KxP4W8O32

Бондаренко

Brill

Dumas³

et al. 2004

Solid State Communications

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“…The Peierls transition is signaled by a small maximum of C p (T ) at T = 310 K, being in rough agreement with the transition temperature T CDW established from resistivity measurements. The relative increase of specific heat at the charge density wave formation temperature denotes ∆Cp Cp(TCDW ) ≃ 1.1%, thus is at the same order of magnitude as in canonical CDW systems as NbSe 3 83 , K 0.9 Mo 6 O 17 84 , or tungsten bronzes 85 .…”

Section: E Specific Heatmentioning

confidence: 88%

Charge density wave and large non-saturating magnetoresistance in YNiC$_2$ and LuNiC$_2$

Kolincio,

Roman,

Klimczuk

2019

Preprint

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We report a study of physical properties of two quasi-low dimensional metals YNiC2 and LuNiC2 including the investigation of transport, magnetotransport, galvanomagnetic and specific heat properties. In YNiC2 we reveal two subsequent transitions associated with the formation of weakly coupled charge density wave at TCDW = 318 K, and its locking in with the lattice at T1 = 275 K. These characteristic temperatures follow the previously proposed linear scaling with the unit cell volume, demonstrating its validity extended beyond the lanthanide-based RNiC2. We also find that, in the absence of magnetic ordering able to interrupt the development of charge density wave, the Fermi surface nesting leads to opening of small pockets, containing high mobility carriers. This effect gives rise to substantial enhancement of magnetoresistance, reaching 470 % for YNiC2 and 50 % for LuNiC2 at T = 1.9 K and B = 9 T.

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Specific heat at CDW transitions in bronzes

Cited by 9 publications

References 4 publications

Microscopic theory of the pseudogap and Peierls transition in quasi-one-dimensional materials

Microscopic theory of the pseudogap and Peierls transition in quasi-one-dimensional materials

Specific heat anomalies in the quasi two-dimensional monophosphate tungsten bronzes KxP4W8O32

Charge density wave and large non-saturating magnetoresistance in YNiC$_2$ and LuNiC$_2$

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