NaV2O5: AN EXOTIC EXCITON SYSTEM

2001 ◽  
Vol 15 (28n30) ◽  
pp. 3732-3736
Author(s):  
MAXIM V. MOSTOVOY ◽  
DANIEL I. KHOMSKII ◽  
JASPER KNOESTER
Keyword(s):  
Phase Transition ◽  
Charge Ordering ◽  
Effective Hamiltonian ◽  
Sodium Vanadate ◽  
Temperature Dependent ◽  
Large Bandwidth ◽  
Gap Opening ◽  
A Charge ◽  
Exciton Type ◽  
Exciton System

We show that the phase transition which sodium vanadate undergoes at Tc=34 K is driven by a charge ordering. The relevant effective Hamiltonian is of the Frenkel exciton type, with a very large bandwidth to molecular energy ratio. This causes stron non-Heitler-London effects and a temperature dependent gap that vanishes at Tc. In addition to the phase transition, the model qualitatively explains the observed absorption spectrum and the anomaly in the static dielectric constant. Within our model, the observed spin-gap opening at Tc results from exciton-spinon coupling.

Charge ordering and superconductivity in α-(BEDT-TTF)$_2M$Hg(SCN)4

2002 ◽  
Vol 12 (9) ◽  
pp. 57-60
Author(s):  
M. Dressel ◽  
N. Drichko ◽  
B. Salameh ◽  
J. Thorns ◽  
J. Schlueter ◽  
...  
Keyword(s):  
Phase Transition ◽  
Optical Properties ◽  
Quantum Phase Transition ◽  
Optical Conductivity ◽  
Short Range ◽  
Charge Ordering ◽  
Extended Hubbard Model ◽  
A Charge ◽  
Ordering Transition ◽  
Exact Diagonalisation

In the optical spectra of the non-superconducting salt α-(BEDT-TTF)2KHg(SCN)4 a strong feature appears at frequencies of about 200 cm-1 and temperatures below 200 K which indicates the opening of a pseudogap. This is in contrast to the superconducting α-(BEDT-TTF)2NH4Hg(SCN)4 whch exhlbits metallic-like optical properties down to 2 K. Based on exact diagonalisation calculations of the optical conductivity on an extended Hubbard model at quarter-filling we argue that the proximity of these salts to a charge ordering transition is responsible for the observed pseudogap. Our proposed scenario suggests that the different ground states, including superconductivity, are a consequence of the fluctuations associated with short range charge ordering which builds up close to the quantum phase transition.

Temperature-Dependent Solid-state Luminescence and Reversible Phase Transition of (n-Bu4N)[Au(SC6H3-3,5-Me2)2]

2003 ◽  
Vol 32 (11) ◽  
pp. 1002-1003 ◽  
Author(s):  
Seiji Watase ◽  
Takayuki Kitamura ◽  
Nobuko Kanehisa ◽  
Masami Nakamoto ◽  
Yasushi Kai ◽  
...  
Keyword(s):  
Phase Transition ◽  
Solid State ◽  
Temperature Dependent ◽  
Reversible Phase Transition ◽  
Reversible Phase ◽  
State Luminescence

scholarly journals Ultrafast spot-profile LEED of a charge-density wave phase transition

2021 ◽  
Vol 118 (22) ◽  
pp. 221603
Author(s):  
G. Storeck ◽  
K. Rossnagel ◽  
C. Ropers
Keyword(s):  
Phase Transition ◽  
Charge Density ◽  
Charge Density Wave ◽  
Density Wave ◽  
Wave Phase ◽  
Charge Density Wave Phase ◽  
A Charge

Low Temperature Phase Transition (Pt) and Defect Formation (Df) in Silicon with Dioxide Inclusions Under X-Ray Irradiation

1995 ◽  
Vol 396 ◽  
Author(s):  
SH.M. Makhkamov ◽  
S.N. Abdurakhmanova
Keyword(s):  
Phase Transition ◽  
Charge Exchange ◽  
Defect Formation ◽  
Exchange Process ◽  
Temperature Phase ◽  
X Rays ◽  
Charge Exchange Process ◽  
X Ray ◽  
Temperature Phase Transition ◽  
A Charge

AbstractStudies of galvanomagnetic and electrical parameters of p- type Si : SiO2 in the temperature range 80 – 400 K have shown that X-ray irradiation at 80 K (Mo Ka,β and braking radiation hvmax. = 50 heV) leads to various transformations of the spectrum of electron- hole states in the band gap of such material, depending on the flux density of the X-rays. Two main processes are observed: the defect (vacancy and divacancy) formation and a charge exchange of native defects localized at the Si – SiO2 interface. The charge exchange process is rather collective and stimulated one because it is in response to an X-ray-induced ferroelectric phase transition in the SiO2- phase.

Possible low-temperature phase transition of Langmuir–Blodgett films of a charge–transfer complex detected by ESR

1998 ◽  
Vol 327-329 ◽  
pp. 391-394
Author(s):  
Keiichi Ikegami ◽  
Shin-ichi Kuroda ◽  
Tomoyuki Akutagawa ◽  
Taro Konuma ◽  
Takayoshi Nakamura ◽  
...  
Keyword(s):  
Phase Transition ◽  
Charge Transfer ◽  
Low Temperature ◽  
Charge Transfer Complex ◽  
Temperature Phase ◽  
Langmuir Blodgett ◽  
Langmuir Blodgett Films ◽  
Temperature Phase Transition ◽  
A Charge ◽  
Low Temperature Phase

scholarly journals Temperature Dependence of Electrical Properties and Crystal Structure of 0.29Pb(In1/2Nb1/2)O3–0.44Pb(Mg1/3Nb2/3)O3–0.27PbTiO3Single Crystals

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
Qian Li ◽  
Yun Liu ◽  
Andrew Studer ◽  
Zhenrong Li ◽  
Ray Withers ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Electrical Properties ◽  
Dielectric Permittivity ◽  
Neutron Diffraction ◽  
Electrical Measurement ◽  
Temperature Dependent ◽  
Electromechanical Properties ◽  
Polar Order

We characterized the temperature dependent (~25–200°C) electromechanical properties and crystal structure of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3single crystals usingin situelectrical measurement and neutron diffraction techniques. The results show that the poled crystal experiences an addition phase transition around 120°C whereas such a transition is absent in the unpoled crystal. It is also found that the polar order persists above the maximum dielectric permittivity temperature at which the crystal shows a well-defined antiferroelectric behavior. The changes in the electrical properties and underlying crystal structure are discussed in the paper.

The variational approach to the Glashow–Weinberg–Salam model

1987 ◽  
Vol 65 (4) ◽  
pp. 395-402 ◽  
Author(s):  
R. Manka ◽  
J. Sladkowski
Keyword(s):  
Phase Transition ◽  
Effective Potential ◽  
Variational Approach ◽  
Canonical Quantization ◽  
Temperature Dependent ◽  
Model Based

The variational approach to the Glashow–Weinberg–Salam model, based on canonical quantization, is presented. It is shown that taking into consideration the Becchi–Rouet–Stora symmetry leads to the correct, temperature-dependent, effective potential. This generalization of the Weinberg–Coleman potential leads to a phase transition of the first kind.

scholarly journals Ionic Conductivity and Phase Transition Behaviour in 4AgI-(1-)-2CuI System

2008 ◽  
Vol 2008 ◽  
pp. 1-4 ◽  
Author(s):  
Mohammed Hassan ◽  
Rfi Rafiuddin
Keyword(s):  
Phase Transition ◽  
Ionic Conductivity ◽  
Binary System ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Conductivity Measurements ◽  
Temperature Dependent ◽  
X Ray ◽  
Dsc Curves ◽  
Transition Behaviour

Samples of general formula 4AgI-(1-)-2CuI, , have been prepared and investigated by XRD, DSC, and temperature-dependent conductivity studies. X-ray diffractograms showed the presence of binary system consisting of AgI and in the sample . Cu-substituted samples showed very similar diffractograms to that of the pure compound which indicates that no effect for the substitution on the nature of the binary system. DSC curves showed the presence of phase transition whose temperature increased with ratio in the system. Ionic conductivity measurements confirmed the occurrence of the phase transition and showed that the high temperature phase is superionic conducting, whose conductivity increases with the increasing amount in the system.

Synthesis, Structure and Magnetic Properties of Monoclinic Nb12O29

2000 ◽  
Vol 658 ◽  
Author(s):  
J. E. L. Waldron ◽  
M. A. Green
Keyword(s):  
Magnetic Properties ◽  
Magnetic Order ◽  
Bulk Sample ◽  
Charge Ordering ◽  
Rapid Reduction ◽  
One Dimensional ◽  
Range Magnetic Order ◽  
A Charge ◽  
Ordering Transition ◽  
Long Range Magnetic Order

ABSTRACTThe synthesis, structure and magnetic properties of monoclinic Nb12O29 are described. The synthesis of a pure bulk sample is difficult due to the large number of other similar phases. It is achieved by rapid reduction of H-Nb2O5 with Nb metal. The compound is shown to undergo a charge ordering transition at low temperature which provokes long range magnetic order in an intriguing one dimensional arrangement.

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