Thermal properties of 1T-TaS2 at the onset of charge density wave states

Rayappan, John Bosco Balaguru; Raj, S. Alfred Cecil; Lawrence, Nathan S.

doi:10.1016/j.physb.2010.04.044

Cited by 10 publications

(6 citation statements)

References 17 publications

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“…Figures 11(a)-(c) show the resulting space and time dependence of the lattice temperature in the uppermost 200 nm of the sample for λ ⊥ values of 1, 3.9 and 11.5 W K −1 m −1 . The first λ ⊥ value is the best fit to our experimental results, whereas the latter two values represent the measured minimum and maximum values for the in-plane heat conductivity of 1T-TaS 2 at temperatures of 100 and 180 K, respectively [81,82] (the out-of-plane heat conductivity has not been measured). Figure 11(d) shows the corresponding temporal evolutions of the lattice temperature within the first nanometer of the sample, i.e.…”

Section: Heat Diffusion Dynamicsmentioning

confidence: 60%

“…We expect that around this temperature the photo-induced CDW/PLD phase should transform back into the CCDW phase. Not surprisingly, the simple 1D heat diffusion model with constant λ ⊥ does not capture this phase transition at which the heat conduction coefficient and also the dimensionality of the problem may change [81,82]. Nevertheless, the agreement between experiment and simulation on the sub-750 ps timescale is strong evidence that the observed long-term relaxation dynamics of the 'spectroscopic order parameter' CDW is governed by heat diffusion.…”

Section: Heat Diffusion Dynamicsmentioning

confidence: 99%

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Time-resolved x-ray photoelectron spectroscopy at FLASH

et al. 2012

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Coherent and incoherent excitations of the Gd(0001) surface on ultrafast timescales Uwe Bovensiepen -Time-resolved HAXPES at SACLA: probe and pump pulse-induced space-charge effects L-P Oloff, M Oura, K Rossnagel et al. Abstract. The technique of time-resolved pump-probe x-ray photoelectron spectroscopy using the free-electron laser in Hamburg (FLASH) is described in detail. Particular foci lie on the macrobunch resolving detection scheme, the role of vacuum space-charge effects and the synchronization of pump and probe lasers. In an exemplary case study, the complete Ta 4f core-level dynamics in the layered charge-density-wave (CDW) compound 1T-TaS 2 in response to impulsive optical excitation is measured on the sub-picosecond to nanosecond timescale. The observed multi-component dynamics is related to the intrinsic melting and reformation of the CDW as well as to extrinsic pump-laser-induced vacuum space-charge effects.

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Section: Heat Diffusion Dynamicsmentioning

confidence: 60%

Section: Heat Diffusion Dynamicsmentioning

confidence: 99%

Time-resolved x-ray photoelectron spectroscopy at FLASH

et al. 2012

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“…The data for decreasing temperature, presented in [52], give for the I-CDW and NC-CDW comparable values within the experimental error. For the low temperature C-CDW phase, the McMillan formula yields, with µ * = 0.20 [63] and a Debye temperature Θ D of 249 K [46,64,65], a superconducting critical temperature T c = 1.2 K, in fair agreement with the value at normal pressure of 1.5 K reported by Nagata et al [47]. For the high-pressure (5 GPa) NC-CDW phase, Rossnagel derives from the McMillan formula and the input data Tc = 5 K, μ * = 0.20 and ΘD = 249 K, an e-ph interaction constant λ = 0.85 [63], also in agreement with the present value of λ for the NC-CDW phase, although HAS experiments are performed in vacuum conditions.…”

Section: T-tas 2 (001)mentioning

confidence: 99%

Measuring the Electron–Phonon Interaction in Two-Dimensional Superconductors with He-Atom Scattering

et al. 2020

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Helium-atom scattering (HAS) spectroscopy from conducting surfaces has been shown to provide direct information on the electron–phonon interaction, more specifically the mass-enhancement factor λ from the temperature dependence of the Debye–Waller exponent, and the mode-selected electron–phonon coupling constants λQν from the inelastic HAS intensities from individual surface phonons. The recent applications of the method to superconducting ultra-thin films, quasi-1D high-index surfaces, and layered transition-metal and topological pnictogen chalcogenides is briefly reviewed.

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“…Instead, the Cp/T (T) curve shows a moderate decrease followed by a clear change of the slope at TCDW ~ 150 K. Similar discontinuous decrease/increase (depending on the rise/decrease of temperature) of the specific heat in the vicinity of TCDW was observed in the case of incommensurate-to-commensurate transition in 2H-TaSe2 22 . Moreover, a discontinuity in the specific heat of 1T-TaS2 was predicted by the calculation based on the Born von Karman model 23 . Upon further cooling, the Cp/T (T) curve reveals a sharp drop at ~ 50 K, which may be related to the upturn in the magnetic susceptibility at a similar temperature range.…”

Section: Resultsmentioning

confidence: 91%

The low-temperature highly correlated quantum phase in the charge-density-wave 1T-TaS2 compound

et al. 2017

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A prototypical quasi-2D metallic compound, 1T-TaS 2 has been extensively studied due to an intricate interplay between a Mottinsulating ground state and a charge-density-wave order. In the low-temperature phase, 12 out of 13 Ta 4+ 5d-electrons form molecular orbitals in hexagonal star-of-David patterns, leaving one 5d-electron with S = ½ spin free. This orphan quantum spin with a large spin-orbit interaction is expected to form a highly correlated phase of its own. And it is most likely that they will form some kind of a short-range order out of a strongly spin-orbit coupled Hilbert space. In order to investigate the low-temperature magnetic properties, we performed a series of measurements including neutron scattering and muon experiments. The obtained data clearly indicate the presence of the short-ranged phase and put the upper bound on~0.4 µ B for the size of the magnetic moment, consistent with the orphan-spin scenario.npj Quantum Materials (2017)2:42 ; doi:10.1038/s41535-017-0048-1 INTRODUCTIONThe instability of charge density waves (CDW) found in lowdimensional electron systems of layered materials has attracted enormous attention recently. 1T-TaS 2 is a prototypical quasi-2D metallic compound with a strong electron-phonon coupling responsible often for CDW instabilities. Upon cooling, it undergoes a series of first-order phase transitions to CDW, Mott and superconducting phases (see e.g., ref. 1 and references therein).1T-TaS 2 bulk crystal has a lamellar structure, with each layer composed of a triangular lattice of Ta atoms which is then sandwiched by S atoms in an octahedral TaS 6 coordination with a weak Van der Waals bonding between the layers. Above~540 K, the structure is unmodulated trigonal with P-3m1 symmetry; below which the triangular lattice exhibits a series of structural modulations.2, 3 First, an incommensurate CDW phase sets in at T 540 K. Upon further cooling, the structure changes to a nearly commensurate phase at T nCDW~3 50 K. Finally, the material turns into a Mott insulating phase with in-plane √13 × √13 superlattice distortion, which coexists with a commensurate CDW phase below T CDW~1 80 K. Superconductivity emerges in 1T-TaS 2 below~2 K by introducing disorders.4 Recent angle-resolved photoemission spectroscopy experiments suggest that the melted Mott state and the superconductivity coexist in real space 5 providing better understanding of the interplay between electron correlation, charge order, and superconductivity. Unlike other Mott insulators, the CDW superlattices play the role of localization centers in the ground state of 1T-TaS 2 .According to the current understanding, the CDW phase is composed of molecular orbitals of 13 Ta atoms, forming a hexagonal pattern of so-called David-star clusters. As proposed more than three decades ago, 6 each Ta 4+ of 1T-TaS 2 provides one 5d electron, and thus there are 13 5d-electrons per each David star. Out of these 13 electrons, 12 electrons form 6 covalent bonds

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Thermal properties of 1T-TaS2 at the onset of charge density wave states

Cited by 10 publications

References 17 publications

Time-resolved x-ray photoelectron spectroscopy at FLASH

Time-resolved x-ray photoelectron spectroscopy at FLASH

Measuring the Electron–Phonon Interaction in Two-Dimensional Superconductors with He-Atom Scattering

The low-temperature highly correlated quantum phase in the charge-density-wave 1T-TaS2 compound

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