Electron diffraction and Raman scattering evidence of a symmetry breaking at the metal-insulator transition ofNdNiO3

2001 ◽  
Vol 64 (8) ◽  
Author(s):  
M. Zaghrioui ◽  
A. Bulou ◽  
P. Lacorre ◽  
P. Laffez
Keyword(s):  
Electron Diffraction ◽  
Symmetry Breaking ◽  
Raman Scattering ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator

scholarly journals Structural characterization of heat-treated activated carbon fibers

1992 ◽  
Vol 7 (7) ◽  
pp. 1788-1794 ◽  
Author(s):  
A.M. Rao ◽  
A.W.P. Fung ◽  
M.S. Dresselhaus ◽  
M. Endo
Keyword(s):  
Heat Treatment ◽  
Activated Carbon ◽  
Raman Scattering ◽  
Carbon Fibers ◽  
Insulator Transition ◽  
Activated Carbon Fibers ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Sequence Of Events ◽  
Heat Treated

Raman scattering, x-ray diffraction, and BET measurements are used to study the effect of heat treatment on the microstructure of activated carbon fibers (ACFs) and to correlate the structural changes with the metal-insulator transition observed in the electronic transport properties of heat-treated ACFs. A sequence of events is identified, starting with desorption, followed by micropore collapse plus the stacking of basic structural units in the c-direction, and ending up with in-plane crystallization. The graphitization process closely resembles that depicted by Oberlin's model, except that the final material at high-temperature heat treatment remains turbostratic. Because the metal-insulator transition was observed to occur at heat-treatment temperature THT ≃ 1200 °C, which is well below the THT value (2000 °C) for in-plane crystallization, we conclude that this electronic transition is not due to in-plane ordering but rather to the collapse of the micropore structure in the ACFs. Raman scattering also provides strong evidence for the presence of local two-dimensional graphene structures, which is the basis for the transport phenomena observed in heat-treated ACFs.

Symmetry breaking in the metal-insulator transition ofBaVS3

2002 ◽  
Vol 66 (7) ◽  
Author(s):  
T. Inami ◽  
K. Ohwada ◽  
H. Kimura ◽  
M. Watanabe ◽  
Y. Noda ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator

scholarly journals Metal–Insulator Transition in Three-Dimensional Semiconductors

Symmetry ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1345
Author(s):  
Klaus Ziegler
Keyword(s):  
Symmetry Breaking ◽  
Spontaneous Symmetry Breaking ◽  
Critical Point ◽  
Order Parameter ◽  
Three Dimensional ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metallic Behavior ◽  
Metal Insulator ◽  
Scattering Rate

We use a random gap model to describe a metal–insulator transition in three-dimensional semiconductors due to doping, and find a conventional phase transition, where the effective scattering rate is the order parameter. Spontaneous symmetry breaking results in metallic behavior, whereas the insulating regime is characterized by the absence of spontaneous symmetry breaking. The transition is continuous for the average conductivity with critical exponent equal to 1. Away from the critical point, the exponent is roughly 0.6, which may explain experimental observations of a crossover of the exponent from 1 to 0.5 by going away from the critical point.

Raman-scattering study of the metal-insulator transition inBa1−xKxBiO3

1992 ◽  
Vol 46 (2) ◽  
pp. 1232-1235 ◽  
Author(s):  
S. Tajima ◽  
M. Yoshida ◽  
N. Koshizuka ◽  
H. Sato ◽  
S. Uchida
Keyword(s):  
Raman Scattering ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Scattering Study
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