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An interlayer tunneling technique has been used for spectroscopy of charge density wave (CDW) energy gaps (Δ1,2) in NbSe3 subsequently opened at the Fermi surface on decreasing temperature at T
p1 = 145 K (CDW1) and at T
p2 = 60 K (CDW2). We found that the CDW2 formation is accompanied by an increase of the CDW1 gap below T
p2. The maximum enhancement of Δ1, δΔ1 is about 10%. The effect observed has been predicted theoretically as resulting from the joint phase locking of both CDWs
with the underlying crystalline lattice below T
p2.
The text was submitted by the authors in English. 相似文献
3.
《Solid State Communications》1986,57(1):27-30
We have performed detailed measurements of the dc current-voltage (I–V) characteristics of NbSe3 in the hysteretic switching regime. Within the hysteresis loop, we observe a series of well-defined and quasi-stable current-carrying states, each with a unique I–V relationship. Transitions between the states, induced by both the applied electric field and thermal fluctuations, are observed. Rapid and random transitions between closely spaced levels are suggested to result in excessive current or voltage noise for the depinned charge density wave condensate. 相似文献
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《Solid State Communications》1976,19(6):479-481
The far-infrared reflectivity of 1T-TaS2 was measured at 100, 295 and 390 K. At the two highest temperatures, the spectra were featureless. Overall reflectivity dropped abruptly in cooling through 350 K and through 190 K. These transitions are correlated to CDW formation. At 100 K five strong bands and at least two weak bands were observed. These are attributed to lattice vibration which can be excited optically as a result of the breakdown of selection rules due to the formation of a large superlattice by the onset of CDW. 相似文献
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Inelastic neutron scattering measurements have been carried out on 1T-TiSe2 at various temperatures in order to obtain information about the dynamics of the phase transition associated with the charge density waves. A large damping of a transverse phonon at the L-point has been observed near the transition temperature. A simple lattice dynamical model was used to study the effect of the Ti-Se bonding on the transition. 相似文献
8.
The in-plane and out-of-plane resistivities of both 2H-TaSe2 and 2H-NbSe2 were determined down to 10 K. For both compounds, the resistivity anisotropy shows notably a slope change at temperatures where a CDW transition is expected to occur. On the other hand, for both compounds the resistivity anisotropy at the lowest temperature of measurement is much greater than expected by the Lawrence–Doniach model, which relates the critical magnetic field anisotropy to the normal state resistivity anisotropy for 3D-anisotropic superconductors. 相似文献
9.
Borisenko SV Kordyuk AA Yaresko AN Zabolotnyy VB Inosov DS Schuster R Büchner B Weber R Follath R Patthey L Berger H 《Physical review letters》2008,100(19):196402
Using angle-resolved photoemission spectroscopy we demonstrate that a normal-state pseudogap exists above T(N-IC) in one of the most studied two-dimensional charge-density wave (CDW) dichalcogenides 2H-TaSe(2). The initial formation of the incommensurate CDW is confirmed as being driven by a conventional nesting instability, which is marked by a pseudogap. The magnitude, character, and anisotropy of the 2D-CDW pseudogap bear considerable resemblance to those seen in superconducting cuprates. 相似文献
10.
P. Miller B. Janko B.L. Gyorffy 《Physica C: Superconductivity and its Applications》1993,210(3-4):343-349
We study a simple tight-binding (Hubbard) model for electrons interacting via a short range attractive potential. We show that on a cubic lattice, for a half-filled band the ground state may feature both superconductivity and a charge density wave. We examine the response of such a ground state to an external magnetic field and describe the effect of the charge density wave on the Meissner effect. 相似文献
11.
We have studied by pulsed NMR a single crystal of 2HNbSe2 at ambient pressure and under hydrostatic pressure of 21 kbar in the temperature range 4.2–273 K. Our results are consistent with the onset of incommensurate charge density waves (ICDW) at TCDW = 33 K atP = 1 bar and 26 K at P = 21 kbar. Below TCDW, the lineshapes of the (m → m ? 1) transitions agree with a local distribution of Knight shift and electric field gradients respecting the symmetry of a triple ICDW, while above TCDW, pre-transitional broadening is observed. The product T1T = 500 ± 100 msk was found constant in the temperature range 4.2–77 K and pressure independant. 相似文献
12.
We consider a model in which an electric field induces quantum nucleation of kink-antikink pairs in a pinned charge or spin density wave. Pair nucleation events, prevented by Coulomb blockade below a pair creation threshold, become correlated in time above threshold. The model provides a natural explanation for the observed (i) small density wave polarization below threshold in NbSe (3), (ii) narrow band noise, (iii) coherent oscillations, and (iv) mode-locking at high drift frequencies. 相似文献
13.
We investigate collective effects
in the strong pinning model of disordered charge
and spin density waves (CDWs and SDWs) in connection with heat relaxation
experiments.
We discuss the classical and quantum limits that
contribute to two distinct contribution to the specific heat (a Cv
T-2 contribution and a Cv T contribution respectively),
with two different types of disorder (strong pinning versus
substitutional impurities).
From the calculation of the two level system energy splitting distribution
in the classical limit
we find no slow relaxation
in the commensurate case and a broad spectrum of relaxation times
in the incommensurate case. In the commensurate case quantum effects
restore a non vanishing energy relaxation, and
generate stronger disorder
effects in incommensurate systems.
For substitutional disorder we obtain
Friedel oscillations
of bound states close to the Fermi energy.
With negligible interchain couplings
this explains the power-law specific heat Cv T
observed in experiments on CDWs and SDWs
combined to the power-law susceptibility
(T)T-1+ observed in the CDW o-TaS3. 相似文献
14.
S. A. Brazovskii S. I. Matveenko 《Journal of Experimental and Theoretical Physics》2003,96(3):555-563
We consider pseudogap effects for electrons interacting with gapless modes. We study generic 1D semiconductors with acoustic phonons and incommensurate charge density waves. We calculate the subgap absorption as it can be observed by means of photoelectron or tunneling spectroscopy. Within the formalism of functional integration and adiabatic approximation, the probabilities are described by nonlinear configurations of an instanton type. Particularities of both cases are determined by the topological nature of stationary excited states (acoustic polarons or amplitude solitons) and by the presence of gapless phonons that change the usual dynamics to the quantum dissipation regime. Below the free-particle edge, the pseudogap starts with an exponential (stretched exponential for gapful phonons) decrease of the transition rates. Deeply within the pseudogap, they are dominated by a power law, in contrast to a nearly exponential law for gapful modes. 相似文献
15.
B. Riccó 《Solid State Communications》1977,22(5):331-333
The Fermi energy of niobium diselenide is calculated and the result is used to compute the wave-vector dependent susceptibility χ(q). This is found to have a fairly narrow peak at a wave-vector in very good agreement with that of the periodic lattice distortion developed by the solid at low temperature and such a peak can be seen to arise from good nesting of the Fermi surface. 相似文献
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We demonstrate the creation of a charge density wave (CDW) along a stack of coupled Josephson junctions (JJs) in layered superconductors. Electric charge in each superconducting layer oscillates around some average value, forming a breathing CDW. We show the transformation of a longitudinal plasma wave to CDW in the state corresponding to the outermost branch. Transition between different types of CDW’s related to the inner branches of IV characteristic is demonstrated. The effect of the external electromagnetic radiation on the states corresponding to the inner branches differs crucially from the case of the single JJ. The Shapiro steps in the IV characteristics of the junctions in the stack do not correspond directly to the frequency of radiation ω. The system of JJs behaves like a single whole system: the Shapiro steps or their harmonics in the total IV characteristics appear at voltage $\sum {V_l } = N_R \frac{m} {n}\omega$ , where V l is the voltage in the lth junction, N R is the number of JJs in the rotating state, and m and n are integers. 相似文献
18.
The electrical resistivities of Hf-doped and W-doped 1T-TaS2 have been measured to investigate the influence of varying the Fermi level on the formation of commensurate charge density waves. It was found that W-doping is far more effective in breaking the C-CDW phase than Hf-doping. Such results are explained by the energy consideration of the system with the Hubbard gap which is produced by the Mott-localization. 相似文献
19.
We report on the measurement of the nuclear quadrupole interaction by TDPAC on a single crystal of 1T-TaS2 before and after bombardment with 70 MeV16O6+ ions. In 1T-TaS2, two groups of inequivalent Ta-sites are observed at 298 K due to the presence of a nearly commensurate charge density wave
(CDW) Upon16O6+ bombardment a single slightly broadened line is observed which resembles closely the incommensurate CDW state. 相似文献
20.
The effect of charge density waves has been observed in X-ray photoelectron spectra of 1T-TaS2 and TaSe2 as a perturbation of the core-electron binding energies. In the commensurate CDW range the Ta 4f levels show a marked splitting; in the quasi-commensurate and incommensurate states they show broadening of magnitude comparable to this splitting. 相似文献