scholarly journals Evolution of a band insulating phase from a correlated metallic phase

2007 ◽  
Vol 76 (16) ◽  
Author(s):  
Kalobaran Maiti ◽  
Ravi Shankar Singh ◽  
V. R. R. Medicherla
Keyword(s):  
Metallic Phase ◽  
Insulating Phase

Spin Fluctuation Effect on Electrical Resistivity of La0.8Ca0.2MnO3 Manganite Nanoparticles

2015 ◽  
Vol 14 (04) ◽  
pp. 1550010 ◽  
Author(s):  
K. K. Choudhary
Keyword(s):  
Experimental Data ◽  
Electrical Resistivity ◽  
Temperature Regime ◽  
Spin Fluctuation ◽  
Metallic Phase ◽  
Spin Fluctuations ◽  
Electron Interaction ◽  
Manganite Nanoparticles ◽  
Wide Range ◽  
Insulating Phase

The electrical resistivity ρ(T) of La 0.8 C 0.2 MnO 3 manganite nanoparticles (particle size 18 nm and 70 nm) significantly depends on temperature and size of nanoparticles. ρ(T) of 70 nm La 0.8 C 0.2 MnO 3 manganite exhibits metallic phase in low temperature regime (T < 250 K ), develops a maxima near 250 K and decrease with T at high temperatures (250 K < T < 300 K ). However, the ρ(T) of 18 nm La 0.8 C 0.2 MnO 3 manganite shows insulating phase in overall temperature regime, where resistivity decrease with temperature. The resistivity in metallic phase is theoretically analyzed by considering the strong spin fluctuations effect which is modelled using Drude–Lorentz type function. In addition to the spin fluctuation-induced contribution the electron-phonon and electron-electron ρe-e(T) = BT2 contributions are also incorporated for complete understanding of experimental data. The contributions to the resistivity by inherent acoustic phonons (ρac) as well as high frequency optical phonons (ρop) were estimated using Bloch–Gruneisen [BG] model of resistivity. It is observed that the resistivity contribution due to electron-electron interaction shows typical quadratic temperature dependence. Resistivity in Semiconducting/insulating phase is discussed with small polaron conduction (SPC) model. Finally the theoretically calculated resistivity compared with experimental data which found consistent in wide range of temperature.

Photo-modulated dynamic competition between metallic and insulating phases in a layered manganite

2014 ◽  
Vol 1636 ◽  
Author(s):  
Yuelin Li ◽  
Donald Walko ◽  
Qing’an Li ◽  
Yaohua Liu ◽  
Stephan Rosenkranz ◽  
...  
Keyword(s):  
Optical Excitation ◽  
Superlattice Reflection ◽  
Metallic Phase ◽  
Local Competition ◽  
Ultrafast Optical ◽  
Laser Fluences ◽  
Show Evidence ◽  
Jahn Teller ◽  
Insulating Phase ◽  
Reflection Intensity

ABSTRACTWe show evidence that the competition between the antiferromagnetic metallic phase and the charge- and orbital-ordered insulating phase at the reentrant phase boundary of a layered manganite, LaSr2Mn2O7, can be manipulated using ultrafast optical excitation. The time-dependent evolution of the Jahn-Teller superlattice reflection, the indicator of the formation of charge and orbital order, was measured at different laser fluences. The laser-induced change in the Jahn-Teller reflection intensity shows a reversal of sign between earlier (∼10 ns) and later (∼150 ns) times during the relaxation of the sample. This is consistent with a physics picture whereby the laser excitation modulates the local competition between the metallic and the insulating phases.

scholarly journals Approximating metal–insulator transitions

2015 ◽  
Vol 29 (06) ◽  
pp. 1550036 ◽  
Author(s):  
Carlo Danieli ◽  
Kristian Rayanov ◽  
Boris Pavlov ◽  
Gaven Martin ◽  
Sergej Flach
Keyword(s):  
Localization Length ◽  
System Size ◽  
Metallic Phase ◽  
Iteration Step ◽  
Spatial Period ◽  
Metal Insulator ◽  
One Dimensional ◽  
Slowing Down ◽  
Quantum Wave ◽  
Insulating Phase

We consider quantum wave propagation in one-dimensional quasiperiodic lattices. We propose an iterative construction of quasiperiodic potentials from sequences of potentials with increasing spatial period. At each finite iteration step, the eigenstates reflect the properties of the limiting quasiperiodic potential properties up to a controlled maximum system size. We then observe approximate Metal–Insulator Transitions (MIT) at the finite iteration steps. We also report evidence on mobility edges, which are at variance to the celebrated Aubry–André model. The dynamics near the MIT shows a critical slowing down of the ballistic group velocity in the metallic phase, similar to the divergence of the localization length in the insulating phase.

TWO-DIMENSIONAL LOCALIZATION: SYNTHESIS OF OLD AND NEW RESULTS

2003 ◽  
Vol 17 (25) ◽  
pp. 4491-4507 ◽  
Author(s):  
VIPIN SRIVASTAVA ◽  
RAISHMA KRISHNAN
Keyword(s):  
Electron Density ◽  
Disordered Systems ◽  
Metallic Phase ◽  
Experimental Results ◽  
Two Dimensional ◽  
Central Question ◽  
Electron Densities ◽  
Insulating Phase

We have addressed the central question in two-dimensional disordered systems: whether all states are localized even at infinitesimal disorder, as has been believed for over two decades but has come in question after recent experiments. We argue that the answer could still be yes since above a certain density the electrons can be treated effectively as non-interacting. Below this density, though the interactions among electrons get weaker they become more and more important as the electron density reduces. This can cause delocalization and produce a metallic phase. Some recent experimental results have been analysed to understand the nature of the newly found metallic phase at low electron-densities, and also the insulating phase at lower densities.

scholarly journals Корреляционная природа фазового перехода изолятор--металл в пленках V-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-

2020 ◽  
Vol 62 (8) ◽  
pp. 1284
Author(s):  
А.В. Ильинский ◽  
Е.Б. Шадрин
Keyword(s):  
Phase Transition ◽  
Metallic Phase ◽  
Metal Phase ◽  
Temperature Hysteresis ◽  
Complex Character ◽  
Thermal Phase ◽  
Metal Phase Transition ◽  
Characteristic Features ◽  
Insulating Phase ◽  
Two Stages

Abstract A complex character of the mechanism of thermal phase transformations from the insulating phase to the metallic phase has been revealed in thin V_2O_3 films. The insulator–metal phase transition in V_2O_3 is shown to consist of two stages: the hysteresis-less temperature-extended electron Mott transition extended in temperature and the stepwise structural Peierls transition with temperature hysteresis. The features of the insulator–metal phase transition revealed for V_2O_3 are discussed. These features are analyzed on the base of their comparison with characteristic features of analogous phase transition in VO_2 films.

HIGH-RESOLUTION ANGLE-RESOLVED PHOTOEMISSION STUDY OF BaCo1-xNixS2

2002 ◽  
Vol 09 (02) ◽  
pp. 1127-1132
Author(s):  
T. SATO ◽  
H. KUMIGASHIRA ◽  
D. IONEL ◽  
T. ITO ◽  
T. TAKAHASHI ◽  
...  
Keyword(s):  
Phase Transition ◽  
Fermi Surface ◽  
Metallic Phase ◽  
Layered Compounds ◽  
Photoemission Spectroscopy ◽  
Common Features ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Carrier Doping ◽  
Photoemission Study ◽  
Insulating Phase

We have performed angle-resolved photoemission spectroscopy on a layered Mott system BaCo 1-x Ni x S 2 across the phase transition from the antiferromagnetic insulator (x = 0.18) to anomalous metal (x = 0.28). In the anomalous metallic phase, we found a large Fermi surface centered at the M(A) point with a dominant Co (Ni) 3d3z2-r2 character. Hubbard bands in the insulating phase have a remnant of Fermi surface in the metallic phase and gradually evolve into metallic dispersive bands upon carrier doping. We conclude that the electronic structure of BaCo 1 - x Ni x S 2 is basically different from that of the high-Tc cuprates although the transport and magnetic properties share some common features between the two layered compounds.

ELECTRONIC STRUCTURES OF THE METAL-TO-INSULATOR TRANSITION SYSTEM 1T-TaSxSe2-x STUDIED BY ANGLE-RESOLVED PHOTOEMISSION SPECTROSCOPY

2002 ◽  
Vol 09 (02) ◽  
pp. 1085-1089 ◽  
Author(s):  
K. HORIBA ◽  
K. ONO ◽  
M. OSHIMA ◽  
Y. AIURA ◽  
O. SHIINO
Keyword(s):  
Electronic Structures ◽  
Density Wave ◽  
Metallic Phase ◽  
Photoemission Spectroscopy ◽  
Gap Formation ◽  
Hubbard Band ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Charge Density Wave Phase ◽  
Lower Hubbard Band ◽  
Insulating Phase

We have investigated the electronic structures of metal-to-insulator transitions (MIT) due to charge-density-wave phase transition in 1T- TaS x Se 2-x by angle-resolved photoemission spectroscopy. In the insulating phase of the sample with x = 1.5, we observe a gap formation at the Fermi energy (E F ), while in the metallic phase of the sample with x = 1.2, we do not observe a drastic change in the spectra between at room temperature and at low temperature. We observe a peak originating from the lower Hubbard band in the insulating phase of the sample with x = 1.5. In the metallic phase of the sample with x = 1.2, the peak intensity is smaller and the peak energy shifts near E F , but the lower Hubbard band peak still remains. These results suggest that MIT in 1T- TaS x Se 2-x is due to the Mott localization.

scholarly journals Quantum Criticality in Twisted Transition Metal Dichalcogenides

2021 ◽  
Author(s):  
Abhay Pasupathy ◽  
Augusto Ghiotto ◽  
En-Min Shih ◽  
Giancarlo Pereira ◽  
Daniel Rhodes ◽  
...  
Keyword(s):  
Low Temperature ◽  
Room Temperature ◽  
Quantum Phase Transitions ◽  
Transition Metal Dichalcogenides ◽  
Metallic Phase ◽  
Residual Resistivity ◽  
Metal Insulator ◽  
Metal Dichalcogenides ◽  
Half Filling ◽  
Insulating Phase

Abstract In moiré heterostructures, gate-tunable insulating phases driven by electronic correlations have been recently discovered. Here, we use transport measurements to characterize the gate-driven metal-insulator transitions and the metallic phase in twisted WSe2 near half filling of the first moiré subband. We find that the metal-insulator transition as a function of both density and displacement field is continuous. At the metal-insulator boundary, the resistivity displays strange metal behaviour at low temperature with dissipation comparable to the Planckian limit. Further into the metallic phase, Fermi-liquid behaviour is recovered at low temperature which evolves into a quantum critical fan at intermediate temperatures before eventually reaching an anomalous saturated regime near room temperature. An analysis of the residual resistivity indicates the presence of strong quantum fluctuations in the insulating phase. These results establish twisted WSe2 as a new platform to study doping and bandwidth controlled metal-insulator quantum phase transitions on the triangular lattice.

scholarly journals Recent Progress on Vanadium Dioxide Nanostructures and Devices: Fabrication, Properties, Applications and Perspectives

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 338
Author(s):  
Yanqing Zhang ◽  
Weiming Xiong ◽  
Weijin Chen ◽  
Yue Zheng
Keyword(s):  
Phase Transition ◽  
Vanadium Dioxide ◽  
Optical Transmittance ◽  
Structural Features ◽  
Metallic Phase ◽  
Smart Windows ◽  
Future Studies ◽  
Challenges And Opportunities ◽  
Low Dimensional ◽  
Insulating Phase

Vanadium dioxide (VO2) is a typical metal-insulator transition (MIT) material, which changes from room-temperature monoclinic insulating phase to high-temperature rutile metallic phase. The phase transition of VO2 is accompanied by sudden changes in conductance and optical transmittance. Due to the excellent phase transition characteristics of VO2, it has been widely studied in the applications of electric and optical devices, smart windows, sensors, actuators, etc. In this review, we provide a summary about several phases of VO2 and their corresponding structural features, the typical fabrication methods of VO2 nanostructures (e.g., thin film and low-dimensional structures (LDSs)) and the properties and related applications of VO2. In addition, the challenges and opportunities for VO2 in future studies and applications are also discussed.

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