Temperature and momentum dependence of the spectral function of the charge-density wave and of the normal α phase of Pb/Ge(111)

1997 ◽  
Vol 55 (7) ◽  
pp. 4109-4112 ◽  
Author(s):  
A. Goldoni ◽  
C. Cepek ◽  
S. Modesti
Keyword(s):  
Charge Density ◽  
Spectral Function ◽  
Charge Density Wave ◽  
Density Wave ◽  
Momentum Dependence ◽  
Α Phase

scholarly journals Unitarity bound violation in holography and the instability toward the charge density wave

2020 ◽  
Vol 35 (22) ◽  
pp. 2050128
Author(s):  
Geunho Song ◽  
Yunseok Seo ◽  
Sang-Jin Sin
Keyword(s):  
Field Theory ◽  
Conformal Field Theory ◽  
Fermi Surface ◽  
Charge Density ◽  
Spectral Function ◽  
Charge Density Wave ◽  
Density Wave ◽  
Surface Phenomena ◽  
Unitarity Bound ◽  
Conformal Field

We study the spectral function of holographic fermions with Pauli term. We find the [Formula: see text]-dependent instability signaled by the tachyonic spectrum ([Formula: see text]-gap) from the [Formula: see text] regime where unitarity is violated. We suggest that this is the instability toward the charge density wave (CDW) based on the similarity of the unitarity violation in conformal field theory (CFT) and the nesting Fermi surface phenomena in weakly interaction system: both of them give divergent enhancement of degree of freedom.

Dispersion of superconducting gap excitations in layered charge density wave systems

1983 ◽  
Vol 61 (8) ◽  
pp. 1160-1168 ◽  
Author(s):  
G. C. Mahanty ◽  
S. N. Behera
Keyword(s):  
Charge Density ◽  
Spectral Function ◽  
Charge Density Wave ◽  
Energy Gap ◽  
Density Wave ◽  
Exact Expression ◽  
Experimental Result ◽  
Layered Compound ◽  
Present Calculation ◽  
Peak Structure

The phonon spectral function for charge density wave (CDW) systems in the superconducting (SC) phase is calculated for finite wave vectors (q). An exact expression for the q dependent phonon self-energy is obtained. The analysis is carried out with a small q limit. The spectral function shows a two peak structure for frequencies co less than the SC energy gap (2Δ) in contrast to the single peak obtained by Balseiro and Falicov for q = 0. The peaks approach each other with increasing q and finally merge into one. Both modes have linear dispersions for small q and the frequency of the low-lying one goes to zero as q → 0. For ω > 2Δ the phonon spectrum does not change significantly. The results are discussed in context with the Raman scattering observation of SC gap excitations in 2H–NbSc2 (a layered compound exhibiting both CDW and SC transitions) by Sooryakumar and Klein. The present calculation demands that the strength of coupling between the CDW phonon and SC electrons be an order of magnitude smaller than that used for q = 0 in order to get an agreement with the experimental result.

scholarly journals van der Waals driven anharmonic melting of the 3D charge density wave in VSe2

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Josu Diego ◽  
A. H. Said ◽  
S. K. Mahatha ◽  
Raffaello Bianco ◽  
Lorenzo Monacelli ◽  
...  
Keyword(s):  
Charge Density ◽  
First Principles ◽  
Charge Density Wave ◽  
Van Der Waals ◽  
Density Wave ◽  
Transition Metal Dichalcogenides ◽  
Van Der Waals Interactions ◽  
Large Momentum ◽  
Momentum Dependence ◽  
Main Challenge

AbstractUnderstanding of charge-density wave (CDW) phases is a main challenge in condensed matter due to their presence in high-Tc superconductors or transition metal dichalcogenides (TMDs). Among TMDs, the origin of the CDW in VSe2 remains highly debated. Here, by means of inelastic x-ray scattering and first-principles calculations, we show that the CDW transition is driven by the collapse at 110 K of an acoustic mode at qCDW = (2.25 0 0.7) r.l.u. The softening starts below 225 K and expands over a wide region of the Brillouin zone, identifying the electron-phonon interaction as the driving force of the CDW. This is supported by our calculations that determine a large momentum-dependence of the electron-phonon matrix-elements that peak at the CDW wave vector. Our first-principles anharmonic calculations reproduce the temperature dependence of the soft mode and the TCDW onset only when considering the out-of-plane van der Waals interactions, which reveal crucial for the melting of the CDW phase.

scholarly journals Emergent charge order from correlated electron-phonon physics in cuprates

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
S. Banerjee ◽  
W. A. Atkinson ◽  
A. P. Kampf
Keyword(s):  
Fermi Surface ◽  
Charge Density ◽  
Charge Density Wave ◽  
High Temperature Superconductors ◽  
Density Wave ◽  
Charge Order ◽  
Charge Density Waves ◽  
Charge Ordering ◽  
Momentum Dependence ◽  
Electronic Correlations

Abstract Charge-density wave order is now understood to be a widespread feature of underdoped cuprate high-temperature superconductors, although its origins remain unclear. While experiments suggest that the charge-ordering wavevector is determined by Fermi-surface nesting, the relevant sections of the Fermi surface are featureless and provide no clue as to the underlying mechanism. Here, focusing on underdoped YBa2Cu3O6+x, we propose that charge-density waves form from the incipient softening of a bond-buckling phonon. The momentum dependence of its coupling to itinerant electrons favourably selects the wavevector found in experiments. But, it requires quasiparticle renormalization by strong electronic correlations to enable a unique enhancement of the charge susceptibility near the B1g-phonon selected wavevector. The B1g phonon frequency softens by a few percent, and finite-range charge-density wave correlations will form locally, if nucleated by defects or dopant disorder. These results suggest that underdoped cuprates cannot be understood in the context of strong electronic correlations alone.

Observation of Multiple Charge Density Wave Phases in Epitaxial Monolayer 1T-VSe2 Film

2021 ◽  
Author(s):  
Junyu Zong ◽  
Yang Xie ◽  
Qinghao Meng ◽  
Qichao Tian ◽  
Wang Chen ◽  
...  
Keyword(s):  
Charge Density ◽  
Charge Density Wave ◽  
Density Wave ◽  
Deep Understanding ◽  
Spatial Modulation ◽  
Scanning Tunneling ◽  
Momentum Dependence ◽  
Significant Information ◽  
Step Transition ◽  
Gap Structure

Abstract As a special order of electronic correlation induced by spatial modulation, the charge density wave (CDW) phenomena in condensed matters attract enormous research interests. Here, using scanning-tunneling microscopy in various temperatures, we observe a new (2×1) CDW phase besides the (√7×√3) CDW phase in epitaxial monolayer 1T-VSe2 film. Combining the variable-temperature angle-resolved photoemission spectroscopic (ARPES) measurements, we discover an anisotropic CDW gap and a two-step transition associated with the different CDW phases, which were observed below 135 K for the (√7×√3) CDW phase and between 135 K to 330 K for the (2×1) CDW phase respectively. The (√7×√3) CDW phase results a full gap, while the (2×1) CDW phase shows highly momentum dependence and results a partial gap structure at the Fermi surface. This two-step transition with anisotropic gap opening and the resulted evolution in ARPES spectra are corroborated by our theoretical calculation based on a phenomenological form for the self-energy containing a two-gap structure. Our findings provide significant information and deep understanding on the CDW phases in monolayer 1T-VSe2 film as a 2D material.

Spectral function of the charge-density-wave (CDW) phonon in an anisotropic CDW superconductor

1984 ◽  
Vol 30 (11) ◽  
pp. 6387-6396 ◽  
Author(s):  
X. L. Lei ◽  
C. S. Ting ◽  
Joseph L. Birman
Keyword(s):  
Charge Density ◽  
Spectral Function ◽  
Charge Density Wave ◽  
Density Wave
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