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Tytuł:
Metal-Insulator Transition in Doped Semiconductors
Autorzy:
Jaroszyński, J.
Powiązania:
https://bibliotekanauki.pl/articles/1888088.pdf
Data publikacji:
1991-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
Opis:
A survey is given of different kinds of metal-insulator transitions (MIT) in doped semiconductors. The role of electron-electron Coulomb interactions and of disorder is discussed vis-a-vis millikelvin experimental results for semimagnetic semiconductors (SMSC) in the vicinity of MIT. Critical behavior of conductivity tensor components and dielectric susceptibility at the magnetic field-induced MIT in p-type Hg$\text{}_{1-x}$Mn$\text{}_{x}$Te is compatible with the model in which the MIT is a result of quantum localization driven by disorder-modified electron-electron interactions. At the same time the critical behavior of the Hall coefficient suggests that, in addition to electrons forming the Fermi liquid (FL) and undergoing localization at the MIT, there is certain a concentration of local electron moments, even on the metallic side of the MIT. The formation of these moments can presumably be described in terms of a disordered Hubbard-Mott model.
Źródło:
Acta Physica Polonica A; 1991, 80, 2; 255-265
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlation-Driven Metal-Insulator Transitions
Autorzy:
Honig, J. M.
Powiązania:
https://bibliotekanauki.pl/articles/2011236.pdf
Data publikacji:
2000-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
71.45.Gm
Opis:
The effect of correlation-driven electronic transitions are described for the V$\text{}_{2}$O$\text{}_{3}$, NiS$\text{}_{2-x}$Se$\text{}_{x}$, and Fe$\text{}_{3}$O$\text{}_{4}$ systems. The various tranformations can all be rationalized in terms of elementary concepts pertaining to the Mott-Hubbard intraatomic electronic interactions or in terms of an order-disorder formalism involving Coulomb interactions among electrons on adjacent sites. Attention is directed to some outstanding issues that require further resolution.
Źródło:
Acta Physica Polonica A; 2000, 97, 1; 141-156
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Conductivity Near the Metal-to-Insulator Transition in Cd$\text{}_{1-x}$Mn$\text{}_{x}$Se:Sc
Autorzy:
Głód, P.
Sawicki, M.
Lenard, A.
Dietl, T.
Plesiewicz, W.
Powiązania:
https://bibliotekanauki.pl/articles/1887158.pdf
Data publikacji:
1991-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
71.55.Jv
Opis:
Earlier studies of transition metal impurities in II-VI compounds suggest that Sc acts as a resonant donor. We performed Hall effect and conductivity measurements of CdSe:Sc and Cd$\text{}_{0.95}$Mn$\text{}_{0.05}$Se:Sc. The results, particularly the critical concentration of the metal-to-insulator transition, turned out to be similar to those obtained previously for Cd$\text{}_{1-x}$Mn$\text{}_{x}$Se doped with hydrogenic-like impurities, such as In and Ga. Therefore, if the ground state of Sc impurity is indeed located above the bottom of the conduction band, our data demonstrate that the metal-to-insulator transition is primarily driven by the scattering, i.e. it corresponds to the Anderson localization.
Źródło:
Acta Physica Polonica A; 1991, 79, 2-3; 389-392
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Global Structure of the Falicov-Kimball Model Ground State Phase Diagram
Autorzy:
Lach, J.
Łyżwa, R.
Jędrzejewski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1929588.pdf
Data publikacji:
1993-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Mb
71.30.+h
Opis:
The two-state spinless Falicov-Kimball model on a one-dimensional lattice is studied by means of well-controlled numerical procedures. Restricted phase diagrams in the grand-canonical ensemble and at zero temperature are constructed. The evolution of these phase diagrams, as the interaction parameter U is varied, including the band structures corresponding to configurations of localized particles (ions) and densities of mobile particles (electrons), is monitored. The changes observed enable us to draw conclusions for the global structure of the phase diagram and to make a qualitative plot of such a diagram. Particular attention is paid to the possibility of conductor-insulator transitions. The results obtained suggest that the system is an insulator for all U only if the electron and ion densities ρ$\text{}_{e}$,ρ$\text{}_{i}$ satisfy the conditions: ρ$\text{}_{e}$ + ρ$\text{}_{i}$ = 1, |ρ$\text{}_{i}$ - 1/2| ≤ δ < 1/2. For all other pairs (ρ$\text{}_{e}$,ρ$\text{}_{i}$) there is a critical U at which the system undergoes a conductor-insulator transition.
Źródło:
Acta Physica Polonica A; 1993, 84, 2; 327-344
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Infrared Reflection of $MnTe_2$ under High Pressure
Autorzy:
Mita, Y.
Ishida, Y.
Kobayashi, M.
Endo, S.
Powiązania:
https://bibliotekanauki.pl/articles/1813955.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
78.30.-j
Opis:
The IR reflection measurements of $MnTe_2$ were performed at room temperature under various pressures. It is observed that the reflectivity increases at the pressure range of 8-25 GPa and becomes almost constant at the higher pressure. The carrier concentrations obtained from the reflectivity spectra at the highest pressure region are the order of $10^{22} cm^{-3}$. Therefore it is concluded that pressure-induced semiconductor-metal transition occurs at the pressure range of 8-25 GPa.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 617-620
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic Phase Transition in Layered Materials 1T-TaS$\text{}_{x}$Se$\text{}_{2-x}$ Probed by Cryogenic STM/STS
Autorzy:
Hasegawa, T.
Shiino, O.
Yamaguchi, W.
Endo, T.
Sugawara, H.
Kitazawa, K.
Powiązania:
https://bibliotekanauki.pl/articles/1968713.pdf
Data publikacji:
1998-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
71.20.-b
Opis:
A metal-insulator transition, Mott transition, in layered materials 1T-TaS$\text{}_{x}$Se$\text{}_{2-x}$ was investigated by cryogenic scanning tunneling microscopy/ spectroscopy. At 77 K, tunneling spectra in the insulating phase showed a conduction band with almost half filling, which becomes narrower as x decreases. Around the transition point x≈1.4 at 77 K, we observed a sign of gap opening without an overshooting peak at zero bias, supporting the Mott localization picture in which a carrier number vanishes at the transition point. From the site-specified scanning tunneling spectroscopy measurements, furthermore, electrons were found to localize at the charge density wave crest positions. In 1T-TaS$\text{}_{2}$, we have also found that both metallic and insulating phases coexist in a nanometer scale just above the transition temperature, 180 K. >From the minimum size of the insulating region, the coherence length of Mott insulating state was evaluated to be≈5 nm.
Źródło:
Acta Physica Polonica A; 1998, 93, 2; 297-305
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlation between Magnetic Phases and Insulator-Metal Transition in La$\text{}_{1}\text{}_{/}\text{}_{3}$ Nd$\text{}_{1}\text{}_{/}\text{}_{3}$ Ca$\text{}_{1}\text{}_{/}\text{}_{3}$ MnO$\text{}_{3}$ Perovskite
Autorzy:
Baszyński, J.
Idzikowski, B.
Toliński, T.
Hoser, A.
Powiązania:
https://bibliotekanauki.pl/articles/2013369.pdf
Data publikacji:
2000-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
75.25.+z
Opis:
The La$\text{}_{1}\text{}_{/}\text{}_{3}$ Nd$\text{}_{1}\text{}_{/}\text{}_{3}$ Ca$\text{}_{1}\text{}_{/}\text{}_{3}$ MnO$\text{}_{3}$ ceramic perovskites are investigated using the neutron diffraction technique and resistance measurements in the temperature range from 260 K down to 5 K. We have found that the integrated intensity of the antiferromagnetic peaks was growing with decreasing temperature and reached the maximum at a temperature about 20 K lower than that of the semiconductor-metal transition and did not vanish at 5 K. The semiconductor-metal transition is correlated with the temperature of the maximum of the lattice c-parameter and the percolation of ferromagnetic domains. Our results suggest that although the ferromagnetic long-range order is established through the semiconductor-metal transition induced percolation network, locally the antiferromagnetic correlation can remain.zapisz
Źródło:
Acta Physica Polonica A; 2000, 97, 5; 779-782
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Neutron Diffraction Study of Ferromagnetic Ordering in La$\text{}_{1}\text{}_{/}\text{}_{3}$ Nd$\text{}_{1}\text{}_{/}\text{}_{3}$ Ca$\text{}_{1}\text{}_{/}\text{}_{3}$ MnO$\text{}_{3}$ Induced by Electric Field
Autorzy:
Baszyński, J.
Idzikowski, B.
Toliński, T.
Hoser, A.
Powiązania:
https://bibliotekanauki.pl/articles/2013692.pdf
Data publikacji:
2000-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
75.25.+z
Opis:
We used the neutron diffraction technique to study the ferromagnetic ordering process in La$\text{}_{1}\text{}_{/}\text{}_{3}$ Nd$\text{}_{1}\text{}_{/}\text{}_{3}$ Ca$\text{}_{1}\text{}_{/}\text{}_{3}$ MnO$\text{}_{3}$ induced by the short impulse of the external electric field E=4 V/cm at a magnetic field H=1.5 T. Our sample was prepared by the standard solid-state reaction. The diffraction measurements at 4 K, carried out for the neutron wavelength λ=0.2442 nm, have revealed the orthorhombic perovskite structure with the unit-cell parameters: a=0.5480 nm, b=0.5550 nm and c=0.7737 nm. We observed that a short impulse of the electric field develops the ferromagnetic ordering in a similar way as the magnetic field up to 4 T. We assume that the increased ferromagnetic ordering induced by the external electric field at a given magnetic field has the same physical origin as in the case of the Zener double exchange. The effect is confirmed by magnetic moment measurements using vibrating sample magnetometer.
Źródło:
Acta Physica Polonica A; 2000, 97, 5; 831-834
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase Diagram of Metal-Insulator Transition in System with Anderson-Hubbard Centers
Autorzy:
Skorenkyy, Yu.
Didukh, L.
Kramar, O.
Dovhopyaty, Yu.
Powiązania:
https://bibliotekanauki.pl/articles/1418528.pdf
Data publikacji:
2012-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.10.Lp
71.30.+h
Opis:
The model of a strongly correlated system in which periodically spaced Anderson-Hubbard centers are introduced into narrow-band metal is considered. Besides the interactions between localized magnetic moments and strong on-site Coulomb interaction, the model takes into account the hybridization of localized and band states. To study the effect of the lattice deformation on the electrical properties of the system, the phonon term and elastic energy have been taken into account. Green functions for band and localized electrons have been found. On this base, the energy spectrum has been investigated as a function of model parameters, temperature and external pressure. The criterion of the metal-insulator transition for an integer value of electron concentration has been derived and the phase diagram of the metal-insulator transition has been built.
Źródło:
Acta Physica Polonica A; 2012, 122, 3; 532-534
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of Quantum Effects in Carbonaceous Materials Near the Metal-Insulator Transition by Means of THz Photoconductivity
Autorzy:
Dorosinets, V.
Ksenevich, V.
Seliuta, D.
Martūnas, Z.
Valušis, G.
Powiązania:
https://bibliotekanauki.pl/articles/1813203.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
72.15.Rn
Opis:
A series of carbonaceous fibers with conductivity tuned to the metal-insulator transition were prepared by heat treatment of chemically modified polymer precursors. Peculiar behaviour of the resistivity versus temperature dependence R(T) at low temperatures suggests quantum corrections to the Drude conductivity due to weak localization and electron-electron interaction dominating in the conductivity. The THz conductivity method is employed to study the modification of the density of states and provides evidence for a strong change in density of states at the Fermi level caused by the quantum effects.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 875-878
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transport and Magnetic Studies of New Mixed-Valence Compounds: K$\text{}_{3}$Cu$\text{}_{8}$Se$\text{}_{6}$, KCu$\text{}_{3}$Se$\text{}_{2}$, K$\text{}_{3}$Cu$\text{}_{8}$Te$\text{}_{6}$ and BaCuS$\text{}_{3-x}$
Autorzy:
Jacyna-Onyszkiewicz, I.
Sidowski, M.
Starodub, W.
Ratuszna, A.
Robaszkiewicz, S.
Powiązania:
https://bibliotekanauki.pl/articles/1955832.pdf
Data publikacji:
1997-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.-g
71.30.+h
Opis:
New mixed-valent copper chalcogenides BaCuS$\text{}_{3-x}$ and K$\text{}_{3}$Cu$\text{}_{8}$X$\text{}_{6}$ with X=Se or Te and KCu$\text{}_{3}$Se$\text{}_{2}$, with chemical patterns corresponding to the recently investigated K$\text{}_{3}$Cu$\text{}_{8}$S$\text{}_{6}$ and KCu$\text{}_{3}$S$\text{}_{2}$, were synthesized. For these new samples the results of resistivity and magnetic susceptibility measurements are presented. For BaCuS$\text{}_{3-x}$, K$\text{}_{3}$Cu$\text{}_{8}$Se$\text{}_{6}$ and KCu$\text{}_{3}$Se$\text{}_{2}$ the metal-insulator transition is observed with the low temperature phase being metallic, which is untypical, whereas K$\text{}_{3}$Cu$\text{}_{8}$Te$\text{}_{6}$ is a metal in the investigated temperature range. The temperature dependence of magnetic susceptibility of the studied samples testifies to their diamagnetic or weakly paramagnetic behaviour.
Źródło:
Acta Physica Polonica A; 1997, 91, 2; 405-408
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electromagnetic Properties of Mesoscopic Cylinder
Autorzy:
Zipper, E.
Stebelski, M.
Lisowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/1968457.pdf
Data publikacji:
1997-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.30.+h
72.10.-d
Opis:
The electromagnetic response of a mesoscopic cylinder made of a normal metal or a semiconductor is studied. The relation between the induced current J(q,w) and the electric field E(q,w) is derived. It is shown that the kernel K(q,w) which determines the properties of the system has a finite limit which implies infinite conductivity. The mesoscopic cylinder by virtue of its topology and small dimensions can support a persistent current. If the coherence of currents from different channels is strong enough a novel effect - the self-sustaining current can be obtained. We show that a mesoscopic multichannel system exhibits some features which bear resemblance to the superconductor.
Źródło:
Acta Physica Polonica A; 1997, 92, 5; 1087-1091
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparative Study of the Electronic Structures of $Fe_3O_4$ and $Fe_2SiO_4$
Autorzy:
Piekarz, P.
Oleś, A.
Parlinski, K.
Powiązania:
https://bibliotekanauki.pl/articles/1536886.pdf
Data publikacji:
2010-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
71.30.+h
71.38.-k
Opis:
The electronic properties of two spinels $Fe_3O_4$ and $Fe_2SiO_4$ are studied by the density functional theory. The local Coulomb repulsion U and the Hund exchange J between the 3d electrons on iron are included. For U = 0, both spinels are half-metals, with the minority $t_{2g}$ states at the Fermi level. Magnetite remains a metal in a cubic phase even at large values of U. The metal-insulator transition is induced by the $X_3$ phonon, which lowers the total energy and stabilizes the charge-orbital ordering. $Fe_2SiO_4$ transforms to a Mott insulating state for U > 2 eV with a gap $Δ_g$ ~ U. The antiferromagnetic interactions induce the tetragonal distortion, which releases the geometrical frustration and stabilizes the long-range order. The differences of electronic structures in the high-symmetry cubic phases and the distorted low-symmetry phases of both spinels are discussed.
Źródło:
Acta Physica Polonica A; 2010, 118, 2; 307-312
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Non-Fermi Liquid Behavior of Correlated Fermions in Applied Field
Autorzy:
Korbel, P.
Spałek, J.
Wójcik, W.
Powiązania:
https://bibliotekanauki.pl/articles/1964622.pdf
Data publikacji:
1997-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
71.30.+h
71.10.Fd
Opis:
We have determined an instability of the Fermi-liquid state of almost localized fermions in an applied magnetic field. It is proposed that a transition to a strongly correlated fermions (statistical-spin-liquid) state takes place at that point. The resultant magnetization curve and the field dependence of the specific heat are calculated and compared with those for CeRu$\text{}_{2}$Si$\text{}_{2}$.
Źródło:
Acta Physica Polonica A; 1997, 92, 2; 323-326
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlated Electron Systems of Different Dimensionalities
Autorzy:
Kurzyk, J.
Wójcik, W.
Spałek, J.
Powiązania:
https://bibliotekanauki.pl/articles/1812297.pdf
Data publikacji:
2008-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.27.+a
71.30.+h
71.10.Fd
Opis:
The optimized single-particle wave functions contained in the parameters of the Hubbard model (hopping integral t and intraatomic interaction U) are determined explicitly in the correlated state for electronic systems of various symmetries and dimensions: Hubbard chain, square and triangular lattices, and the three cubic lattices: SC, BCC, and FCC. In effect, the electronic properties of these structures as a function of the interatomic distance R are obtained. In most cases, the model parameters do not scale linearly with the lattice constant. Also, the atomic part of the total ground state energy changes with the U/t ratio and therefore should be (and is) included in the analysis. The solutions of dimensions D>1 are analyzed by utilizing the approximate Gutzwiller treatment.
Źródło:
Acta Physica Polonica A; 2008, 114, 1; 175-178
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 65

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