Peierls Transition Temperature Research Articles

Thermal Disorder in Finite-Length Carbon Nanowire.

Enhancement in chemisorption is one of the active research areas in carbon materials. To remedy the thermally degraded chemisorption occurring at high temperatures, we report a comprehensive study of kink structures in free-standing monoatomic carbon nanowires upon heating. Our Monte Carlo simulation considers multi-monoatomic carbon chains laterally interacting by van der Waals forces. Our study reveals that carbon nanowires maintain their linearity regardless of chain length at low temperatures, but this is not the case at high temperatures. Disordered kink structure is observed in short carbon chains, especially above the Peierls transition temperature. A severe kink structure may increase the possibility of attaching negatively charged atoms, thereby contributing to the development of next-generation materials for chemisorption at high temperatures. We have also provided an important indication that any physical property of the finite-length carbon chain predicted by ab initio calculation should reconsider the atomic rearrangement due to thermal instability at high temperatures.

Low‐Frequency Current Fluctuations in Quasi‐1D (TaSe4)2I Weyl Semimetal Nanoribbons

AbstractLow‐frequency current fluctuations, i.e., electronic noise, in quasi‐1D (TaSe4)2I Weyl semimetal nanoribbons are discussed. It is found that the noise spectral density is of the 1/f type and scales with the square of the current, SI ~ I2 (f is the frequency). The noise spectral density increases by almost an order of magnitude and develops Lorentzian features near the temperature T ≈ 225 K. These spectral changes are attributed to the charge‐density‐wave phase transition even though the temperature of the noise maximum deviates from the reported Peierls transition temperature in bulk (TaSe4)2I crystals. The noise level, normalized by the channel area, in these Weyl semimetal nanoribbons is surprisingly low, ≈10−9 µm2 Hz−1 at f = 10 Hz, when measured below and above the Peierls transition temperature. The obtained results shed light on the specifics of electron transport in quasi‐1D topological Weyl semimetals and can be important for their proposed applications as downscaled interconnects.

Enhanced Electron Heat Conduction in TaS3 1D Metal Wire.

The 1D wire TaS3 exhibits metallic behavior at room temperature but changes into a semiconductor below the Peierls transition temperature (Tp), near 210 K. Using the 3ω method, we measured the thermal conductivity of TaS3 as a function of temperature. Electrons dominate the heat conduction of a metal. The Wiedemann–Franz law states that the thermal conductivity of a metal is proportional to the electrical conductivity σ with a proportional coefficient of L0, known as the Lorenz number—that is, . Our characterization of the thermal conductivity of metallic TaS3 reveals that, at a given temperature T, the thermal conductivity κ is much higher than the value estimated in the Wiedemann–Franz (W-F) law. The thermal conductivity of metallic TaS3 was approximately 12 times larger than predicted by W-F law, implying . This result implies the possibility of an existing heat conduction path that the Sommerfeld theory cannot account for.

Non-equilibrium charge density wave ground state of quasi-two-dimensional rare-earth tritelluride TbTe3

We have studied the time dependence of the relaxation of the non-equilibrium charge density wave (CDW) toward an equilibrium ground state in TbTe3 when the sample is cooled through the Peierls transition temperature under an electric field down to a given temperature, Texp. We show that when cooled at zero electric field or a value less than the threshold one, Et, for depinning the CDW at Texp, the CDW equilibrium ground state has a single phase in the sample volume. When cooled with an electric field higher than Et, the CDW ground state is in a frozen glass state, which can be destabilized only by reducing the electric field below Et. We tentatively interpret these results by the interaction of the CDW with a well ordered Te–Te discommensuration network.

Forced Diffusion of Correlated Impurities in the Peierls Conductor o-TaS3

It is shown that in orthorhombic TaS3 with quenching defects, when the temperature changes in the region below the Peierls transition temperature T < TP, forced diffusion of defects arises due to their strong interaction with the charge density wave (CDW). The relationships between the concentration of quenching defects, n, the threshold field of the onset of CDW sliding, ET, and the defect-induced shift of TP are determined: ET∝ n and ΔTP∝ n. This set of laws corresponds to the case when quenching defects positions are correlated with the CDW. The ordinary (without thermocycling) diffusion of quenching defects was detected at T ≈ 300 K, its diffusion coefficient and the height of the energy barrier were estimated. This made it possible to clarify the most probable nature of the defects. These are interstitial sulfur impurities introduced during quenching into the van der Waals gap between the chains and partially ordered at T < TP due to interaction with the CDW. This ordering significantly lowers the height of the energy barrier of forced diffusion in comparison with ordinary diffusion when the spatial configuration of the CDW changes during thermocycling. This leads to the appearance of anomalously high low-temperature forced mobility of correlated impurities.

Toward the equilibrium ground state of the charge density waves in rare-earth tritellurides

We show that the charge density wave (CDW) ground state below the Peierls transition temperature, $T_{CDW}$, of rare-earth tritellurides is not at its equilibrium value, but depends on the time where the system was kept at a fixed temperature below $T_{CDW}$. This ergodicity breaking is revealed by the increase of the threshold electric field for CDW sliding which depends exponentially on time. We tentatively explain this behavior by the reorganization of the oligomeric (Te$_x$)$^{2-}$ sequence forming the CDW modulation.

A New Type of Charge-Density-Wave Pinning in Orthorhombic TaS3 Crystals with Quenching Defects

Diminishing in the concentration of quenching defects during thermocycling of orthorhombic TaS$_3$ samples in the temperature range below the Peierls transition temperature $T <T_P$ is observed. It makes it possible to study the character of pinning of the charge density wave (CDW) by these defects. A number of fundamental differences from pinning by ordinary local pinning centers - impurities and point defects - have been found. We conclude that quenching defects are extended (non-local) objects (presumably, dislocations) that can diffuse from the crystal during low-temperature termocycling due to their strong interaction with the CDW, which is intrinsic for the Peierls conductors. The presence of these defects leads to a previously unknown non-local type of CDW pinning that acts on $T_P$ and the threshold field for the onset of the CDW sliding, $E_T$, differently in comparison with the local pinning centers.

Features of Pinning of a Charge-Density Wave in Quasi-Two-Dimensional Compounds

Effects of the collective motion (sliding) of a charge density wave in the TbTe3 quasi-two-dimensional conductor have been studied in a wide temperature interval. Immediately after cooling to temperatures below the Peierls transition temperature TCDW = 336 K, the threshold field Et of sliding initiation of the charge density wave has a nearly linear temperature dependence. The aging of samples at a fixed temperature T0 < TCDW for several hours significantly modifies the sliding of the charge density wave. The threshold field increases significantly and the temperature dependence of Et becomes nonmonotonic, demonstrating a large maximum at T = T0. The observed effect is attributed to the aging-induced formation of an ordered structure (lattice) of defects of the charge density wave and to change in the pinning regime at the melting of this structure.

Magnetoresistance of a Two-Dimensional TbTe3 Conductor in the Sliding Charge-Density Wave Regime

The magnetoresistance of a TbTe3 two-dimensional conductor with a charge-density wave (CDW) has been measured in a wide temperature range and in magnetic fields of up to 17 T. At temperatures well below the Peierls transition temperature and in high magnetic fields, the magnetoresistance exhibits a linear dependence on the magnetic field caused by the scattering of normal charge carriers by “hot” spots of the Fermi surface. In the sliding CDW regime in low magnetic fields, a qualitative change in the magnetoresistance has been observed associated with the strong scattering of carriers by the sliding CDW.

Effect of symmetry on electronic DOS, peierls transition and elastic modulus of carbon nanowires

A Monte Carlo arithmetic method is utilized to investigate the Peierls transition in the linear and circular carbon nanowire respectively. The carbon nanowires interacting with the 6 nearest neighbors in hexagonal structure are spaced by 0.3 nm. Despite the Peierls transition of the linear carbon nanowires is unaffected by the Van der Waal’s force, we discovered that the Peierls transition temperature of the isolated curved nanowire is raised to 910K under curvature. Based on the simulation results, the fluctuation of the atomic position of the atoms are stronger near to the free end boundary condition. Applying stress on the interstitial doped carbon nanowire array examines the elastic modulus which shows above 6TPa. The geometrical effect on the electronic density of states of the kink structural carbon chain is simulated by Harris functional in combination with Local Density Approximation. Two different lengths of branches A and B, are occupied alternatively to generate the asymmetric carbon chain. The ratio of the asymmetric branch length, RAB = A / B, plays an important role in the electronic density of states DOS around Fermi level . The highest DOS(EF) occurs if the RAB equals to 2 and while the Fermi level coincides with the Von-Hove singularity at RAB = 3.

Properties of strained TaS3 samples in the state of charge density wave and in the normal state

The uniaxial strain of quasi-one-dimensional conductor whiskers of orthorhombic TaS3 at a strain higher than e c ~ 0.8% leads to a sharp increase in the coherence of the properties of a charge density wave (CDW), which manifests itself in its motion in fields higher than threshold field E t . During uniaxial elongation, TaS3 is shown to exhibit the following unusual properties even in weak fields: Peierls transition temperature T P depends nonmonotonically on e, one-dimensional fluctuations weaken near T P , and the coherence length of a charge density increases at T < T P . Investigations in fields higher than E t show that the ultracoherent properties of CDW exist in a wide temperature range and are retained when temperature increases up to T P . These properties of CDW make it possible to observe a sharp increase in E t near T P and an almost jumplike increase in E t at T < 90 K. The increase in E t at T P is explained by a decrease in the coherence volume of CDW because of a fluctuational suppression of the Peierls gap.

Finite-temperature coupled-cluster, many-body perturbation, and restricted and unrestricted Hartree-Fock study on one-dimensional solids: Luttinger liquids, Peierls transitions, and spin- and charge-density waves.

One-dimensional (1D) solids exhibit a number of striking electronic structures including charge-density wave (CDW) and spin-density wave (SDW). Also, the Peierls theorem states that at zero temperature, a 1D system predicted by simple band theory to be a metal will spontaneously dimerize and open a finite fundamental bandgap, while at higher temperatures, it will assume the equidistant geometry with zero bandgap (a Peierls transition). We computationally study these unique electronic structures and transition in polyyne and all-trans polyacetylene using finite-temperature generalizations of ab initio spin-unrestricted Hartree-Fock (UHF) and spin-restricted coupled-cluster doubles (CCD) theories, extending upon previous work [He et al., J. Chem. Phys. 140, 024702 (2014)] that is based on spin-restricted Hartree-Fock (RHF) and second-order many-body perturbation (MP2) theories. Unlike RHF, UHF can predict SDW as well as CDW and metallic states, and unlike MP2, CCD does not diverge even if the underlying RHF reference wave function is metallic. UHF predicts a gapped SDW state with no dimerization at low temperatures, which gradually becomes metallic as the temperature is raised. CCD, meanwhile, confirms that electron correlation lowers the Peierls transition temperature. Furthermore, we show that the results from all theories for both polymers are subject to a unified interpretation in terms of the UHF solutions to the Hubbard-Peierls model using different values of the electron-electron interaction strength, U/t, in its Hamiltonian. The CCD wave function is shown to encompass the form of the exact solution of the Tomonaga-Luttinger model and is thus expected to describe accurately the electronic structure of Luttinger liquids.

Anisotropy of conductivity in rare-earth tritellurides in the static and sliding states of the CDW

We show that the isotropic conductivity in the normal state of rare-earth tritelluride RTe3 compounds is broken by the occurrence of the unidirectional charge density wave (CDW) in the (a,c) plane below the Peierls transition temperature. In contrast with quasi-one-dimensional systems, the resistivity anomaly associated with the CDW transition is strong in the direction perpendicular to the CDW wave vector Q (a-axis) and very weak in the CDW wave vector Q direction (c-axis). We qualitatively explain this result by calculating the electrical conductivity for the electron dispersion with momentum-dependent CDW gap as determined by angle-resolved photoemission spectroscopy (ARPES). Nonlinear transport properties in TbTe3 and GdTe3 have been studied along different crystallographic orientations. The pronounced effect of collective CDW motion is observed along c-axis and is absent completely in the perpendicular direction demonstrating the unidirectional character of the CDW. The threshold electric field for CDW sliding is linearly temperature dependent in a wide range of temperature.

Indium doping-induced change in the photoconduction spectra of o-TaS3

Impurities and defects are known to affect the properties of the charge density wave (CDW) state but the influence of impurities on the density of states inside the Peierls gap remains largely unexplored. Here we present an experimental study of the effect of indium impurities on photoconduction spectra of CDW compound orthorhombic TaS3. We use the temperature diffusion method to introduce indium into a sample from preliminary attached In contacts. The concentration of In after 23h of diffusion is found to be nonuniform and strongly dependent on the distance to the contacts. The diffusion affects the spectral range 0.15–0.25eV, increasing the photoconduction amplitude linearly with diffusion time. The optical gap value obtained from the measurements is 2Δ=0.25eV and the tail of states below 2Δ is associated with the impurities in agreement with the Tüttö–Zawadowski theory. Diffusion-induced modification of current–voltage characteristics and decrease of the Peierls temperature are also observed. Neither changes in photoconduction spectra nor in the Peierls transition temperature of the control sample with Au contacts are found.

Spontaneous Breaking of Isotropy Observed in the Electronic Transport of Rare-Earth Tritellurides

We show that the isotropic conductivity in the normal state of rare-earth tritelluride RTe3 compounds is broken by the occurrence of the unidirectional charge density wave (CDW) in the (a, c) plane below the Peierls transition temperature. In contrast with quasi-one-dimensional systems, the resistivity anomaly associated with the CDW transition is strong in the direction perpendicular to the CDW wave vector Q (a axis) and very weak in the CDW wave vector Q direction (c axis). We qualitatively explain this result by calculating the electrical conductivity for the electron dispersion with momentum-dependent CDW gap as determined by angle-resolved photoemission spectroscopy. Similar measurements of in-plane conductivity may uncover the gap anisotropy in other compounds for which angle-resolved photoemission spectroscopy is not available.

Finite-temperature second-order many-body perturbation and Hartree–Fock theories for one-dimensional solids: An application to Peierls and charge-density-wave transitions in conjugated polymers

Finite-temperature extensions of ab initio Gaussian-basis-set spin-restricted Hartree-Fock (HF) and second-order many-body perturbation (MP2) theories are implemented for infinitely extended, periodic, one-dimensional solids and applied to the Peierls and charge-density-wave (CDW) transitions in polyyne and all-trans polyacetylene. The HF theory predicts insulating CDW ground states for both systems in their equidistant structures at low temperatures. In the same structures, they turn metallic at high temperatures. Starting from the "dimerized" low-temperature equilibrium structures, the systems need even higher temperatures to undergo a Peierls transition, which is accompanied by geometric as well as electronic distortions from dimerized to non-dimerized forms. The conventional finite-temperature MP2 theory shows a sign of divergence in any phase at any nonzero temperature and is useless. The renormalized finite-temperature MP2 (MP2R) theory is divergent only near metallic electronic structures, but is well behaved elsewhere. MP2R also predicts CDW and Peierls transitions occurring at two different temperatures. The effect of electron correlation is primarily to lower the Peierls transition temperature.

Influence of irradiation-induced disorder on the Peierls transition in TTF–TCNQ microdomains

The combined influence of electron irradiation-induced defects, substrate-induced strain and finite size effects on the electronic transport properties of individual micron-sized thin film growth domains of the organic charge transfer compound tetrathiafulvalene– tetracyanoquinodimethane (TTF–TCNQ) have been studied. The TTF–TCNQ domains have been isolated and electrically contacted by focused ion beam etching and focused ion and electron-beam-induced deposition, respectively. This allowed us to measure the temperature-dependent resistivity and the current–voltage characteristics of individual domains. The dependence of the resistivity on temperature follows a variable-range hopping behaviour which shows a crossover of the exponents as the Peierls transition is approached. The low temperature behaviour is analysed within the segmented rod model of Fogler, Teber and Shklovskii which was developed for charge-ordered quasi one-dimensional electron crystals (Fogler et al 2004 Phys. Rev. B 69 035413). The effect of substrate-induced biaxial strain on the Peierls transition temperature is discussed with regard to its interplay with the defect-induced changes.

Defect-induced shift of the Peierls transition in TTF–TCNQ thin films

In this paper we investigate the influence of the substrate material and film thickness on the Peierls transition temperature in tetrathiafulvalene–tetracyanoquinodimethane (TTF–TCNQ) thin films, grown by physical vapor deposition. Our analysis shows that the substrate material and the growth conditions strongly influence the film morphology. In particular, we demonstrate that the Peierls transition temperature in thin films is lower than in TTF–TCNQ single crystals. We argue that this effect arises due to defects, which emerge in TTF–TCNQ thin films during the growth process.

Thermal transport properties and electronic structure of W-doped rubidium blue bronzes Rb 0.3Mo 1− xW xO 3 ( x=0, 0.001, 0.003, 0.005)

The thermoelectric power (TEP), electrical resistivity and X-ray photoemission spectrum (XPS) of the W-doped rubidium blue bronzes Rb 0.3Mo 1− x W x O 3 ( x=0, 0.001, 0.003, 0.005) were investigated. It is shown that the Peierls transition is suppressed with the increase in the concentrations of the doped W ions. The sign change of the TEP was observed for all the samples. At low temperature below the Peierls transition, the W-doping makes the obvious decrease in the absolute values of TEP, especially for Rb 0.3Mo 1− x W x O 3 ( x=0.003, 0.005). Furthermore, as compared with the pure blue bronzes, the enlarged difference between Peierls transition temperature ( T p ) and the sign changed temperature ( T s ) in Rb 0.3Mo 0.999W 0.001O 3 bronzes was observed and discussed in detail.

Is the Verwey transition in Fe3O4 magnetite driven by a Peierls distortion?

In this viewpoint article we analyse recent crucial structural, optical and transport experiments onFe3O4 magnetite across theVerwey transition at TV∼120–125 K. We find that all the relevant experimental data are consistent with a model of aPeierls distortion in the cubic spinel lattice, and likewise, some of them evidence againstthe original and still distributed hypothesis of the long range charge orderingorigin of the Verwey transition. An estimated Peierls transition temperature (TP) is comparablewith TV. The Peierls model provides new insight into the electronic properties of magnetite.Application of the Peierls model to some other systems is briefly discussed also.