Insulator-Metal Transition and Conduction Processes in Trans-Polyacetylene

1989 ◽  
Vol 173 ◽  
Author(s):  
Esther M. Conwell ◽  
Howard A Mizes ◽  
Surendar Jeyadev
Keyword(s):  
Density Of States ◽  
Coulomb Potential ◽  
Metallic State ◽  
Interchain Coupling ◽  
Insulator Metal Transition ◽  
In Trans ◽  
A Chain ◽  
Stage 1 ◽  
Pauli Susceptibility ◽  
Good Agreement

ABSTRACTWe show by calculations for a chain of stage-1 (16.7%) potassium-doped (CH)x that the metallic state is obtained by adding to the Su-Schrieffer-Heeger Hamiltonian the Coulomb potential of the doping ions and solitons on other chains. Good agreement with the measured Pauli susceptibility is obtained. Adding interchain coupling is found to lead to essentially the same density of states.

scholarly journals Disorder induced power-law gaps in an insulator–metal Mott transition

2018 ◽  
Vol 115 (44) ◽  
pp. 11198-11202 ◽  
Author(s):  
Zhenyu Wang ◽  
Yoshinori Okada ◽  
Jared O’Neal ◽  
Wenwen Zhou ◽  
Daniel Walkup ◽  
...  
Keyword(s):  
Density Of States ◽  
Power Law ◽  
Fermi Energy ◽  
Scanning Tunneling ◽  
Metallic State ◽  
Mott Insulators ◽  
Tunneling Microscopy ◽  
Insulator Metal Transition ◽  
Many Core ◽  
Core Features

A correlated material in the vicinity of an insulator–metal transition (IMT) exhibits rich phenomenology and a variety of interesting phases. A common avenue to induce IMTs in Mott insulators is doping, which inevitably leads to disorder. While disorder is well known to create electronic inhomogeneity, recent theoretical studies have indicated that it may play an unexpected and much more profound role in controlling the properties of Mott systems. Theory predicts that disorder might play a role in driving a Mott insulator across an IMT, with the emergent metallic state hosting a power-law suppression of the density of states (with exponent close to 1; V-shaped gap) centered at the Fermi energy. Such V-shaped gaps have been observed in Mott systems, but their origins are as-yet unknown. To investigate this, we use scanning tunneling microscopy and spectroscopy to study isovalent Ru substitutions in Sr3(Ir1-xRux)2O7 (0 ≤ x ≤ 0.5) which drive the system into an antiferromagnetic, metallic state. Our experiments reveal that many core features of the IMT, such as power-law density of states, pinning of the Fermi energy with increasing disorder, and persistence of antiferromagnetism, can be understood as universal features of a disordered Mott system near an IMT and suggest that V-shaped gaps may be an inevitable consequence of disorder in doped Mott insulators.

Metallic condensation of Wannier-Mott impurity states in lithium-hexamethylphosphoramide glasses

1977 ◽  
Vol 55 (11) ◽  
pp. 2258-2263 ◽  
Author(s):  
Peter P. Edwards ◽  
Ron Catterall
Keyword(s):  
Tight Binding ◽  
Mott Transition ◽  
Electron Interaction ◽  
Metallic State ◽  
Binding Model ◽  
Impurity States ◽  
Coulombic Repulsion ◽  
Variational Form ◽  
Frozen Solutions ◽  
Good Agreement

A metal to non-metal (MNM) transition observed in frozen solutions of lithium in hexamethylphosphoramide (HMPA) was tentatively interpreted as a Mott transition in which localized Wannier-type impurity states were the source of electrons in the metallic state. In this paper this assertion is examined in greater detail by calculating critical densities (nc) on the basis of a scaled (variational) form of Mott's original criterion for the onset of localization in a dielectrically screened Coulomb potential, and also on the basis of the Hubbard tight-binding model. Mott's model for the transition is based upon the screening properties of a freely propagating gas of metallic electrons. In the Hubbard regime, however, the phenomenon is viewed from the tight-binding limit; the transition from localized to delocalized states occurs when the bandwidth (Δ) of a regular lattice of isolated centres exceeds the value of the intra-atomic Coulombic repulsion integral (U) associated with electron correlation.Both electron-gas (Mott) and tight-binding (Hubbard) approaches give calculated critical densities (5.6 × 1018, 3.2 × 1018 cm−3, respectively) in good agreement with the experimental value (∼3 × 1018 cm−3). These results therefore support the earlier suggestion that the MNM transition in frozen lithium-HMPA solutions is a Mott-transition associated with electron-interaction effects.

Electronic Structure vs Phase in Al3V

1988 ◽  
Vol 141 ◽  
Author(s):  
J.-H. Xu
Keyword(s):  
Electronic Structure ◽  
Bulk Modulus ◽  
Total Energy ◽  
Crystal Structures ◽  
Lattice Constant ◽  
Density Of States ◽  
Phase Stability ◽  
Local Density ◽  
Young Modulus ◽  
Good Agreement

AbstractThe electronic structure of Al3V vs its two different crystal structures (DO22 and Ll2) were investigated using local density total energy approach. The calculated results of the total energy showed that in Al3V the tetragonal DO22 phase is energetically favored as compared to the cubic Ll2 phase, the total energy in the former case is about 60 mRy/F.U. lower than that in the later case. The calculated lattice constant (a=3.72 Å, c=8.20 Å) is in fairly good agreement with experiment (a=3.778 Å, c=8.326 Å),and the bulk modulus (1.3 Mbar) is comparable with the experimental Young modulus (150 GPa) for Al3Ti. Furthermore, it is interesting to note that the density of states at EF in the tetragonal DO22 phase (0.14 states/eV-F.U.) is about one order magnitude smaller than that in the Ll2 phase (2.89 states/eV-F.U.). The electronic structure of Al3V seems to be fairly satisfactory in explaining its phase stability.

PRECURSOR OF ANTIFERROMAGNETIC BANDS IN THE HALF-FILLED TWO-DIMENSIONAL HUBBARD MODEL

1999 ◽  
Vol 13 (27) ◽  
pp. 3183-3192
Author(s):  
BUMSOO KYUNG
Keyword(s):  
Hubbard Model ◽  
Density Of States ◽  
Density Wave ◽  
Spin Density Wave ◽  
Local Maximum ◽  
Two Dimensional ◽  
Intermediate Coupling ◽  
Critical Fluctuations ◽  
Wave Approximation ◽  
Good Agreement

We study the half-filled two-dimensional Hubbard model in the intermediate coupling regime. As temperature is decreased for a two-dimensional half-filled band, two-dimensional critical fluctuations give rise to a strong local maximum in | Im Σ(k F , ω)| at ω=0, leading to a split peak with a pseudogap inside in the spectral function and the density of states. The calculated energy dispersion is in good agreement with that of spin density wave approximation.

Investigation of the Insulator-Metal Transition Mechanism in trans -Polyacetylene

1992 ◽  
Vol 9 (2) ◽  
pp. 90-92 ◽  
Author(s):  
Cui Yunlong ◽  
Lin Senhao ◽  
Zhang Jiahua
Keyword(s):  
Transition Mechanism ◽  
Insulator Metal Transition ◽  
In Trans

MAGNETIC SUSCEPTIBILITY OF YRh2

1993 ◽  
Vol 07 (01n03) ◽  
pp. 834-837
Author(s):  
H. YAMADA ◽  
W. STEINER
Keyword(s):  
Magnetic Susceptibility ◽  
Temperature Dependence ◽  
Density Of States ◽  
Phase Structure ◽  
Magnetic Measurements ◽  
Tight Binding ◽  
The Other ◽  
Spin Fluctuations ◽  
Tight Binding Method ◽  
Good Agreement

Magnetic measurements for YRh2 with the cubic Laves phase structure were performed between 4.2 and 600 K. It was observed that the susceptibility shows a very weak temperature dependence and our data are about 40 % larger than the observed one by Loebich and Raub. On the other hand, the temperature dependence of the susceptibility was also estimated theoretically, by using the density-of-states curve calculated in the tight-binding method and by taking into account the effect of spin fluctuations. A good agreement between our observed and calculated results is obtained.

LATTICE DYNAMICS OF MBa2Cu3O7(M=Y, Gd) and YBa2Cu3O6

1989 ◽  
Vol 03 (08) ◽  
pp. 1277-1286 ◽  
Author(s):  
JIE QIN ◽  
YIMIN JIANG
Keyword(s):  
Density Of States ◽  
Phonon Dispersion ◽  
Experimental Investigations ◽  
Phonon Density ◽  
Phonon Density Of States ◽  
Phonon Dispersion Curves ◽  
Rare Earth Atom ◽  
Range Overlap ◽  
Phonon Properties ◽  
Good Agreement

We have presented a lattice dynamical calculation of phonon dispersion curves and one-phonon density of states for the high-T c superconducting MBa 2 Cu 3 O x (M=Y, Gd : x=7, 6) compounds. The model we used is in the framework of a rigid-ion model which includes long-range Coulomb potential and a short-range overlap. The results of calculation give quite good agreement with the available Raman and infrared data, and the measurements of phonon density of states. These results therefore can serve as a guide for further experimental investigations of the phonon properties in M-Ba-Cu-O (M=rare earth atom) system.

Electronic Structures of β-SiC(001) Surfaces and Al/β-SiC(001) Interface

1994 ◽  
Vol 339 ◽  
Author(s):  
Xiao Hu ◽  
Hong Yan ◽  
Fumio S. Ohuchi
Keyword(s):  
Density Of States ◽  
Electronic Structures ◽  
Surface Density ◽  
Tight Binding ◽  
Bonded Interface ◽  
Surface Reconstructions ◽  
Tight Binding Method ◽  
Theoretical Results ◽  
Good Agreement ◽  
The Ideal

ABSTRACTSurface electronic structures of β-SiC reconstructed (001) surfaces and the Al/β-SiC(001) interface have been investigated by employing a tight-binding method. Distinct surface electronic characteristics corresponding to different surface reconstructions are discussed based on the interpretation of surface density of states. The calculations of the Al/β-SiC (001) interface indicate that aluminum deposition on β-SiC(001) surface may induce the substrate to return to the ideal unreconstructed surface and that Al-C interaction is stronger than Al-Si interaction. Al deposition on C-rich surfaces may form a better bonded interface than that on the Si-rich surfaces. Our findings are in good agreement with available experimental and theoretical results.

Role of Interchain Coupling in the Metallic State of Conducting Polymers

2012 ◽  
Vol 109 (10) ◽  
Author(s):  
Nara Kim ◽  
Byoung Hoon Lee ◽  
Doowhan Choi ◽  
Geunjin Kim ◽  
Heejoo Kim ◽  
...  
Keyword(s):  
Conducting Polymers ◽  
Metallic State ◽  
Interchain Coupling

THE PHOTOLYSIS OF KETENE IN THE PRESENCE OF HYDROGEN

1956 ◽  
Vol 34 (2) ◽  
pp. 113-122 ◽  
Author(s):  
H. Gesser ◽  
E. W. R. Steacie
Keyword(s):  
Methyl Ethyl Ketone ◽  
Methyl Ethyl ◽  
Chain Reaction ◽  
Temperature Range ◽  
A Chain ◽  
Good Agreement

The photolysis of ketene in the presence of hydrogen has been investigated in the temperature range −40° to 207 °C. The main products are CO, C2H4, C2H6, and CH4, with some methyl ethyl ketone at the higher temperatures. Hydrogen and ketene compete for CH2 radicals by the reactions[Formula: see text]with E3 − E2 = 0.8 kcal. At the higher temperatures the reaction[Formula: see text]leads to a chain reaction via[Formula: see text]The value of E6 is found to be 10.2 ± 0.5 kcal. in good agreement with previous work.

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