Thermodynamic study of commensurate-incommensurate phase transitions in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Rb</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">ZnCl</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

We show that there exists a universal mechanism of long-range soliton attraction in threedimensional solids and, therefore, of discontinuity of any commensurate-incommensurate (C-IC) phase transition. This mechanism is due to the strain dependence of the soliton self-energy and specific features of the solid-state elasticity. The role of this mechanism is studied in detail for a class of C-IC transitions where the IC modulation is one-dimensional, the anisotropy in the order parameter space is small, and the symmetry of the systems allows the existence of the Lifshitz invariant. Two other mechanisms of soliton attraction are operative here but the universal mechanism considered in this paper is found to be the most important one in some cases. Comparison with the most extensively studied C-IC transition in K2SeO4 shows that the experimentally observed thermal anomalies can be understood as a result of the smearing of the theoretically predicted discontinuous transition.

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“…The procedure is similar to that exposed in Ref. 22 but keeping in mind the different form of the attraction term.…”

Section: Thermal Anomalies Close To the C-ic Transitionmentioning

confidence: 99%

“…Thus, from previous works (see e.g., Refs. 9,22 ) and from Eq. ( 31) we have approximately (taking n e ≃ n loc ) the electric susceptibility as…”

Section: Thermal Anomalies Close To the C-ic Transitionmentioning

confidence: 99%

Universal mechanism of discontinuity of commensurate-incommensurate transitions in three-dimensional solids: Strain dependence of soliton self-energy

2002

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“…These features have been applied for observing ferroelectric phase transitions specially in the influence of electric field and for measuring latent heat even in the neighborhood of a tricritical point where it is expected to be comparatively small. [11,19,20] The TGS crystal used in this experiment was produced by MolTech GmbH in Berlin. It was of the form of a rectangular parallelepiped with dimensions 7.0 mm × 7.0 mm × 4.0 mm along b × c, b, c and 302 mg in mass.…”

mentioning

confidence: 99%

Memory effect in triglycine sulfate induced by a transverse electric field: specific heat measurement

Gallardo¹,

Martín‐Olalla²,

Romero³

et al. 2008

J. Phys.: Condens. Matter

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The influence of a transverse electric field on the specific heat of triglycine sulfate (TGS) has been studied. The specific heat of TGS has been measured on heating the sample from the ferroelectric to the paraelectric phase after prolonged application of transverse electric field (i.e. perpendicular to the ferroelectric axis). It is shown that the specific heat of TGS can 'remember' the temperature T(s) at which the transverse field was previously applied.

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“…It is explained there in terms of the temperature dependence of the excess heat capacity due to a change of composition of the dilute and polymer-rich phase. Various thermodynamic properties of rubidium tetrachlorozincate (Rb 2 ZnCl 4 ) near a phase transition were studied in [12]. Their figure 7 shows that in case of planar lattices the dependence of heat capacity on temperature exhibit two maxima.…”

Section: Introductionmentioning

confidence: 99%

Canonical Ensemble with Temperature Limitation

Bădescu

Landsberg

2005

Found Phys Lett

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Ideal Bose and Fermi systems are studied on the basis of a canonical ensemble, subject to the condition that their temperature is less than a given temperature T max . A single new parameter (the tau-parameter, τ ) is needed to keep account of the new constraint. The parameter τ is shown to be the exponential of a pseudo-chemical potential that is linearly dependent on temperature. The inclusion of the τ -parameter leads to generalizations of usual thermodynamic quantities (internal energy, heat capacity and entropy) and various particular cases are discussed. The heat capacity of a Bose system can exhibit a maximum at a temperature less than the maximum temperature T max . The number of micro-states in the canonical ensemble is found to increase with τ . The heat capacity c V of a Fermi system of non-interacting spins exhibits a Schottky anomaly. The peak depends on τ , and for some cases c V /k can significantly exceed unity. The influence of τ on the entropy of the Fermi system and on the number of micro-states in the canonical ensemble is significant but not spectacular.

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Thermodynamic study of commensurate-incommensurate phase transitions inRb2ZnCl4

Cited by 10 publications

References 21 publications

Universal mechanism of discontinuity of commensurate-incommensurate transitions in three-dimensional solids: Strain dependence of soliton self-energy

Universal mechanism of discontinuity of commensurate-incommensurate transitions in three-dimensional solids: Strain dependence of soliton self-energy

Memory effect in triglycine sulfate induced by a transverse electric field: specific heat measurement

Canonical Ensemble with Temperature Limitation

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