Effect of substitutional impurities on the low-temperature specific heat of (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">TaSe</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mo>)</mml:mo></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Se, Brown; Jo, Willis; Alavi, B.; Grüner, G.

doi:10.1103/physrevb.37.6551

Cited by 12 publications

(4 citation statements)

References 10 publications

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“…This result is consistent with the observation of a specific-heat anomaly on the doped compound, in the same temperature range as for the pure compound. 16 At the same time it shows that the soft TA z sheet should not be viewed as an anomaly arising from electron-phonon interactions.…”

Section: Resultsmentioning

confidence: 96%

Phonon density of states and low-temperature specific heat of quasi-one-dimensional (TaSe4)2
Lorenzo
¹
,
Currat
²
,
Dianoux
³

et al. 1996
Phys. Rev. B
18
2
6
0
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We report on neutron time-of-flight measurements of the generalized phonon density-of-states ͑PDOS͒ in two compounds, ͑NbSe 4 ͒ 3 I and ͑TaSe 4 ͒ 2 I, with chainlike structure. We assign the origin of a low-frequency steplike structure in the PDOS of both compounds to a flat transverse-acoustic sheet with in-chain polarization. We propose a simple dispersion curve model which accounts for the observed low-frequency PDOS structure and which can be adjusted to reproduce the low-temperature specific-heat anomaly in ͑TaSe 4 ͒ 2 I.

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Section: Resultsmentioning

confidence: 96%

Phonon density of states and low-temperature specific heat of quasi-one-dimensional (TaSe4)2
Lorenzo
¹
,
Currat
²
,
Dianoux
³

et al. 1996
Phys. Rev. B
18
2
6
0
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“…In its pinned state due to randomness and disorder, the CDW exists in many metastable states characterized by local deformations of its phase. Indeed the signature of CDW low-energy excitations (LEE) was recently found [5][6][7] at very low temperature, as a contribution to the specific heat additional to that of phonons, in the family of inorganic CDW compounds TaS3, (TaSe^I, NbSe3, and K0.3M0O3. Moreover, in this temperature range the energy relaxation shows an anomalous long-time response with, in addition, "aging" effects [8].…”

Section: Towards Equilibrium Ground State In Charge-density-wave Systemsmentioning

confidence: 99%

Towards equilibrium ground state in charge-density-wave systems

et al. 1991

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We present a study of energy relaxation in two representative charge-density-wave compounds: TaS3 and NbSei below r=0.5 K. The evolution of the relaxation indicates a crossover between a nonequilibrium state and the thermodynamical equilibrium state when the system has been allowed to age. In the equilibrium state the relaxation is thermally activated with an activation energy of -1 K. We interpret these results as long-time dynamics in the network of charge-density-wave dislocations with a critical temperature close to 0 K. PACS numbers: 72.15.Nj, 64.60.Ht Anomalous slow relaxations have been actively studied for many years in a wide variety of materials, such as polymers, ionic conductors, amorphous semiconductors, and spin glasses, in response to different excitations [1] (mechanical stresses, external electric and magnetic fields, etc.). Recent experiments show that chargedensity-wave (CDW) compounds [2] can be included in this broad class of physical systems [3,4]. The CDW ground state formed below the Peierls transition results from the competition between elastic deformations of the CDW and pinning potentials caused by randomly distributed impurities. In its pinned state due to randomness and disorder, the CDW exists in many metastable states characterized by local deformations of its phase. Indeed the signature of CDW low-energy excitations (LEE) was recently found [5-7] at very low temperature, as a contribution to the specific heat additional to that of phonons, in the family of inorganic CDW compounds TaS3, (TaSe^I, NbSe3, and K0.3M0O3. Moreover, in this temperature range the energy relaxation shows an anomalous long-time response with, in addition, "aging" effects [8]. This term, borrowed from the terminology used in the study of amorphous materials and spin glasses, means that the relaxation-time dependence of the energy relaxation depends on the time duration (waiting time) of the application of the thermal perturbation.In this Letter we report on energy relaxation measurements for two representative CDW systems, i.e., TaS3 and NbSe3 in the temperature range 0.1-1 K and in the time window 1-10 5 s. The relaxation rate clearly shows a crossover between a nonequilibrium state (with waitingtime effects) and the thermodynamic equilibrium state beyond a temperature-dependent waiting time. The time for reaching the ground state increases when T is reduced and is well described by an Arrhenius law with an activation energy of -1 K. We propose that the barriers dominating the relaxation originate from the dynamics between the defects in the CDW superstructure: phase slips or dislocation loops interacting with impurities. By analogy with dynamical properties in random systems in which a hierarchical procedure governs the time evolution, the nonexponential character of the relaxation and the activated behavior of the relaxation rate at equilibrium may indicate that the critical temperature of CDW glassy systems is -0 K.We have studied the energy relaxation between 0.08 and 8 K in a dilution refrigerator after...

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“…In addition, the energy range of the pinned phasons in (TaSe 4 ) 2 I, 0.2-1.1 meV (1 meV = 0.242 THz = 8.065 cm −1 ), deduced from ac-conductivity [11,12] and neutron scattering experiments [13], corresponds well to the temperature (1.8 K) of this specific heat 'anomaly'. The phason interpretation was later questioned as a result of C P -experiments on Nbdoped (TaSe 4 ) 2 I samples [14] indicating a persisting anomalous specific heat behaviour with the maximum of the bump at the same temperature as for the pure compound. As ac-conductivity measurements on the Nb-doped compounds [15] show a shift of the pinned phason mode to higher frequencies, the interpretation of the anomaly in terms of phason excitations is questionable.…”

Section: Introductionmentioning

confidence: 99%

The phonon density of states and low-temperature specific heat: the blue bronze and the platinum chain compound KCP

Requardt

Currat

Monçeau³

et al. 1997

J. Phys.: Condens. Matter

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The quasi-one-dimensional charge-density-wave (CDW) compounds (TaSe 4 ) 2 I, the blue bronze K 0.3 MoO 3 and the platinum chain compound KCP(Br) show a strong deviation from a Debye behaviour of the specific heat C P at temperatures of several degrees Kelvin. To determine the origin of this specific heat 'anomaly' in the case of K 0.3 MoO 3 , we have performed time-of-flight neutron scattering measurements and extracted a generalized phonon density of states (PDOS). The excess over a Debye behaviour at low energies in the generalized PDOS lies at the origin of the observed anomalous specific heat. We have used a simplified dispersion model based on experimental phonon dispersion curves to calculate the low-energy PDOS of the system. The model succeeds in reproducing the observed specific heat anomaly and establishes its lattice phonon origin. Similar calculations of the low-energy PDOS based on available phonon dispersion data for KCP allow us to state that the anomalous behaviour of the specific heat for this compound also has a phonon origin.

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Effect of substitutional impurities on the low-temperature specific heat of (TaSe4)2

Cited by 12 publications

References 10 publications

Phonon density of states and low-temperature specific heat of quasi-one-dimensional (TaSe4)2
Lorenzo
¹
,
Currat
²
,
Dianoux
³

et al. 1996
Phys. Rev. B
18
2
6
0
View full text Add to dashboard Cite

Phonon density of states and low-temperature specific heat of quasi-one-dimensional (TaSe4)2
Lorenzo
¹
,
Currat
²
,
Dianoux
³

et al. 1996
Phys. Rev. B
18
2
6
0
View full text Add to dashboard Cite

Towards equilibrium ground state in charge-density-wave systems

The phonon density of states and low-temperature specific heat: the blue bronze and the platinum chain compound KCP

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Effect of substitutional impurities on the low-temperature specific heat of (TaSe4)2

Cited by 12 publications

References 10 publications

Phonon density of states and low-temperature specific heat of quasi-one-dimensional (TaSe4)2Lorenzo1, Currat2, Dianoux3 et al. 1996Phys. Rev. B18260View full textAdd to dashboardCite

Phonon density of states and low-temperature specific heat of quasi-one-dimensional (TaSe4)2Lorenzo1, Currat2, Dianoux3 et al. 1996Phys. Rev. B18260View full textAdd to dashboardCite

Towards equilibrium ground state in charge-density-wave systems

The phonon density of states and low-temperature specific heat: the blue bronze and the platinum chain compound KCP

Contact Info

Product

Resources

About

Phonon density of states and low-temperature specific heat of quasi-one-dimensional (TaSe4)2
Lorenzo
¹
,
Currat
²
,
Dianoux
³

et al. 1996
Phys. Rev. B
18
2
6
0
View full text Add to dashboard Cite

Phonon density of states and low-temperature specific heat of quasi-one-dimensional (TaSe4)2
Lorenzo
¹
,
Currat
²
,
Dianoux
³

et al. 1996
Phys. Rev. B
18
2
6
0
View full text Add to dashboard Cite