Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl

Refine search results

Journals help

  1. 28 Acta Physica Polonica A

Years help

  1. 1 2017

  2. 1 2016

  3. 3 2014

  4. 2 2012

  5. 7 2010

More...
Authors help

  1. 5 Diko P.

  2. 3 Antal V.

  3. 3 Bezusyy V.

  4. 3 Harań G.

  5. 3 Pisarski P.

More...
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 28

Number of results on page
first rewind previous Page / 2 next fast forward last

Search results

Search:
in the keywords:  74.62.Dh
help Sort By:

help Limit search:
first rewind previous Page / 2 next fast forward last
1
Content available remote

Doped Carrier Formulation of the t-J model: Monte Carlo Study of the Anisotropic Case

100%
Ferraz A., Kochetov E., Maśka M., Mierzejewski M.
Acta Physica Polonica A
|
2008
|
vol. 114
|
issue 1
185-189
EN
We derive a doped carrier representation of the t-J model Hamiltonian. Within this approach the t-J model is described in terms of holes hopping in a lattice of correlated spins, where holes are the carriers doped into the half-filled Mott insulator. This representation of the t-J Hamiltonian is very convenient for underdoped systems since close to half-filling it allows for a controlled treatment of the crucial constraint of no doubly occupied sites. When neglecting the transverse spin-spin interaction, the effective Hamiltonian can be investigated with classical Monte Carlo simulations. We discuss the results obtained for systems consisting of several hundred lattice sites.
2
Content available remote

Inhomogeneous Charge Distribution and Superconductivity in the Boson-Fermion Model

100%
Śledź Ż., Mierzejewski M.
Acta Physica Polonica A
|
2008
|
vol. 114
|
issue 1
219-223
EN
We analyze a boson-fermion model that accounts for the electrostatic potential of the out-of-plane dopant atoms. We investigate whether this approach may explain recent experimental results obtained for the Bi-based high-temperature superconductors. We demonstrate that in contradistinction to purely fermionic models, even weak electrostatic potential of the dopant atoms may be responsible for a significant modulation of the superconducting order parameter.
3
Content available remote

Two-Dimensional Behavior of YBa_{2}Cu_{3}O_{x} Films on SrTiO_{3} Substrates

80%
Mikheenko P. N., Lewandowski S. J.
Acta Physica Polonica A
|
1997
|
vol. 92
|
issue 1
152-156
EN
Long-term (up to 18 months) degradation of textured YBa_{2}Cu_{3}O_{x} films prepared by laser ablation and magnetron sputtering on single crystal SrΤiO_{3}, MgO and Al_{2}O_{3} substrates were investigated. All films at each stage of exposition displayed a clearly visible quasi-2D behavior. From the measurements of the Kosterlitz-Thouless temperature it could be concluded that the oxygen content and density of charge carriers remained constant. It follows that the main consequence of degradation is the omission of some planes from the transport of supercurrent and the samples could be described in the model of layered structure with variable number of conducting planes. Using this model we find that effective thickness of an isolated CuO_{2} plane in samples with greatest internal damage is ≈2Å.
4
Content available remote

Magnetic Properties of Yttrium-Substituted NiZn Ferrites

80%
Jančárik V., Ušák E., Šoka M., Ušáková M.
Acta Physica Polonica A
|
2014
|
vol. 126
|
issue 1
90-91
EN
Polycrystalline NiZn ferrite doped with a small amount of Y^{3+} ions and having the composition of Ni_{0.42}Zn_{0.58}Y_{x}Fe_{2-x}O_{4}, where x=0.00, 0.01, 0.02, 0.04, 0.06, 0.08 and 0.10, was analyzed. Specimens were prepared by the ceramic method. Thermo-magnetic analysis and evaluation of hysteresis loops parameters were chosen as main examination methods in this study. Various parameters, such as Curie temperature T_{C}, coercive field H_{c}, remanent magnetic flux density B_{r}, hysteresis loop area and amplitude/initial permeability were studied at low frequencies.
5
Content available remote

s-Wave Order Parameter in the Presence of a Momentum-Dependent Impurity Scattering Potential

80%
Rudzińska D., Pisarski P., Harań G.
Acta Physica Polonica A
|
2008
|
vol. 114
|
issue 1
149-152
EN
Momentum dependence of the impurity potential leads to the anisotropy of a local density of states in isotropic s-wave superconductors. We complete this result by discussing the influence of a momentum-dependent impurity potential on the s-wave order parameter. The scattering process is considered in the T-matrix approximation, and the model impurity potential consists of two separate terms representing isotropic (on-site) and anisotropic (momentum-dependent) parts of the potential. We show that the effect of the isotropic part on the order parameter is local whereas the influence of the momentum-dependent term is nonlocal.
6
Content available remote

Influence of Iron Substitutions on the Transport Properties of FeTe_{0.65}Se_{0.35} Single Crystals

80%
Bezusyy V., Gawryluk D., Malinowski A., Berkowski M., Cieplak M.
Acta Physica Polonica A
|
2014
|
vol. 126
|
issue 4a
A-76-A-80
EN
We study the ab-plane resistivity and Hall effect in the single crystals of Fe_{1-y}M_yTe_{0.65}Se_{0.35}, where M = Co or Ni (0 ≤ y ≤ 0.21). In case of each dopant two types of crystals, with different crystalline quality, are prepared by Bridgman's method using different cooling rates, fast or slow. The impurities suppress the superconducting transition temperature, T_c, with different rates. T_c reaches zero at markedly different impurity content: only 3 at.% of Ni, and about 14 at.% of Co. In addition, the suppression is somewhat dependent on the crystal cooling rate. The resistivity at the onset of superconductivity rises only weakly with the Co doping, while it increases 10 times faster for Ni. The Hall coefficient R_{H} is positive for Co doping indicating that hole carriers dominate the transport. For Ni R_{H} changes sign into negative at low temperatures for crystals with the Ni content exceeding 6 at.%. The implications of these results are discussed.
7
Content available remote

Codoping Effect of Zn and Pr in YBa_2Cu_3O_{7-δ}

80%
Naik M., Sarode P., Prabhu R., Priolkar K., Vasanthacharya N.
Acta Physica Polonica A
|
2009
|
vol. 115
|
issue 3
742-744
EN
In this paper we present the resistivity data for Pr and Zn codoped compound Y_{1-x}Pr_xBa_2[Cu_{1- y}Zn_y]_3O_{7-δ} with 0 & y & 0.1 and x=0.0, 0.1 and 0.2. The data is analysed in terms of the superconducting critical temperature T_c, residual resistivity ρ_0 and the resistivity slope dρ/dT corresponding to the linear ρ-T region. It is found that for x=0.1 Pr has a minimal influence on the in-plane processes for Zn impurity alone affecting slightly T_c and ρ_0. The slope dρ/dT becomes larger for 0.03 & y & 0.06 leading to larger depining effect and hence slower fall of T_c as a function of y. For x = 0.2 there is a drastic change, ρ_0 becomes abnormally large, dρ/dT becomes negative implying absence of depinning and a totally pinned charge stripes. Superconductivity vanishes at y=0.03. It is concluded that for x = 0.2 Pr converts the system from overdoped to underdoped region leading to the universal superconductor-insulator transition.
8
Content available remote

Resonant States of a Momentum-Dependent Impurity Potential in a d-Wave Superconductor

80%
Pisarski P., Harań G.
Acta Physica Polonica A
|
2008
|
vol. 114
|
issue 1
153-157
EN
Nonmagnetic impurity on-site potential leads to the resonant states in a d-wave superconductor for the unitary scattering limit. We extend the above study to include a momentum dependence of the impurity potential and discuss the existence and number of resonant states for a tetragonal anisotropy of the scattering potential.
9
Content available remote

Thermoelectric Power of MgB_2 Single Crystals Doped with Holes and Electrons

80%
Oganisian K., Rogacki K., Sulkowski C., Zhigadlo N., Katrych S., Karpinski J.
Acta Physica Polonica A
|
2008
|
vol. 114
|
issue 1
191-195
EN
The thermoelectric power of MgB_2 single crystals, non-substituted, single-substituted with C, and co-substituted with C and Li, was investigated in the temperature range from 10 to 300 K. Both the in-plane (S_ab) and the out-of-plane (S_c) thermoelectric powers are positive for non-substituted crystals and both S_ab and S_c change a sign for crystals doped with electrons when C is substituted for B in the amount larger than 6 at.%. The substitution of C, which supplies electrons mainly into the σ band, reduces the thermoelectric power anisotropy, most likely by increasing the interband scattering. When Li is additionally co-substituted for Mg, S_ab remains unchanged but S_c increases substantially. The Li substitution donates holes into the π band rather than into the σ band and in this way modifies the π band properties, including the possible increase in the intraband scattering.
10
Content available remote

Universal Critical Quantum Properties of Cuprate Superconductors

80%
Schneider T.
Acta Physica Polonica A
|
1997
|
vol. 91
|
issue 1
203-212
EN
Using the scaling theory of quantum critical phenomena we explore the occurrence of universal critical behavior at the insulator-to-superconductor and superconductor-to-normal state transitions at zero temperature. Experimentally, these phase transitions are driven by doping and correspond to critical end points of the phase transition line in the temperature-hole concentration plane. Provided that the order parameter is a complex scalar in two dimensions, and that the London relation between superfluid number density and magnetic penetration depth holds, the scaling theory predicts universal behavior close to the insulator-to-superconductor transition. In particular, transition temperature and zero temperature penetration depth are universally related and the sheet resistance adopts a universal value. These predictions agree remarkably well with available experimental data and provide useful constraints for a microscopic theory.
11
Content available remote

Muon Spin Rotation Studies of Doping in High-T_{c} Superconductors

80%
Niedermayer C.
Acta Physica Polonica A
|
1999
|
vol. 96
|
issue 2
213-227
EN
Muon spin rotation studies on high temperature superconducting cuprates will be reviewed. After an introduction to the technique, studies on the superfluid density will be described and the universal variation of the superfluid density n_{s} as a function of p will be presented. Important exceptions will be discussed, such as the YBa_{2}Cu_{3}O_{7-δ} system, where, besides the intrinsically superconducting CuO_{2} planes, an interlayer may be metallised (here the CuO chains) which consequently contributes to a significant enhancement in superfluid density and associated improvement in technologically interesting properties such as flux pinning and critical current density. Evidence for an unconventional pairing state, possibly with d-wave symmetry, is presented from studies of the rapid suppression of superfluid density due to the substitution of structural inhomogeneities (such as Zn) that introduce strong scattering centers within the CuO_{2} planes. Finally, the phase diagram of the antiferromagnetic correlations and, in particular, their coexistence with the superconducting state, will be discussed in terms of muon spin rotation experiments in zero external magnetic field.
12
Publication available in full text mode
Content available

Quasiparticle Interference in a Superconducting State with a Fourfold Phase Change

80%
Pisarski P., Harań G.
Acta Physica Polonica A
|
2007
|
vol. 111
|
issue 5
791-794
EN
Quantum interference revealed in Bi_2Sr_2Ca Cu_2O_{8+δ} by Fourier transform scanning spectroscopy is primarily determined by maxima of the joint density of states which correspond to an octet of scattering wave vectors connecting points at the constant quasiparticle energy contours where the density of states is maximal. We consider a superconductor with a constant quasiparticle density of states where the interference is due to the fourfold change in the phase of the order parameter. Our results may be helpful in a discussion of the interference in a d-wave superconductor at the tunneling energy exceeding the gap magnitude.
13
Publication available in full text mode
Content available

The Isotope Effect of Disordered Superconductors

80%
Mierzyńska M., Wysokiński K.
Acta Physica Polonica A
|
2004
|
vol. 106
|
issue 5
647-652
EN
The isotope effects in disordered weak and strong coupling superconductors of different symmetries of the order parameter have been studied. We have found that even though weak localisation corrections to Eliashberg equations describe a strong degradation of transition temperature with disorder of s-wave superconductors, their influence on isotope coefficient is relatively weak. On the other hand the calculated change of relative isotope coefficient with T_c/T_{c0} in homogeneous thin film materials is similar to that observed in high temperature superconductors.
14
Content available remote

Light-Induced Gratings in CdMnTeSe:In Crystals

80%
Koziarska-Glinka B., Ponder M., Wojtowicz T., Miotkowski I., Langer J. M., Suchocki A.
Acta Physica Polonica A
|
1997
|
vol. 92
|
issue 5
883-886
EN
We show that DX-like centers in Cd_{1-x}Mn_{x}Te_{1-y}Se_{x}:In crystal can be used in writing volume holographic gratings. The scattering efficiency is higher than 10% which proves the dispersive character of the light-induced gratings. Two different metastable centers with different lattice relaxation were found in the crystal. Measurements of the power dependence of the degenerate four-wave mixing scattering efficiency testify that both of these centers have negative U properties.
15
Content available remote

Photostriction of CdF_{2}:In Crystals

80%
Suchocki A., Raułuszkiewicz J., Langer J., Koziarska-Glinka B.
Acta Physica Polonica A
|
1997
|
vol. 92
|
issue 5
1005-1008
EN
Lattice relaxation accompanying phototransformation of In bistable centers from the ground, deep state to the shallow state in CdF_{2} crystal has been measured with the use of scanning tunnelling microscope. It is shown that relatively small macroscopic changes of the crystal length in the order of 1.8×10^{-6} accompany the phototransformation of In ions. Lattice expansion upon the influence of population of shallow donor levels in CdF_{2} explains the observed small changes of lattice constant during the process.
16
Content available remote

The Doped YBCO Superconductor Crystal Structure Simulation

80%
Kavečanský V., Diko P.
Acta Physica Polonica A
|
2010
|
vol. 118
|
issue 5
1034-1035
EN
Pinning process plays an important role in improving utility properties of YBa_2Cu_3O_{7-δ} (YBCO) superconductors. As a consequence of the low coherent length, the most effective pinning centers in such type of materials should have nanometer size dimensions. An efficient way of introducing such centers can be a chemical substitution in the YBCO lattice. Computer simulation of locally distorted YBCO crystal structure due to the substitutions has been performed.
17
Content available remote

Point Contact Spectroscopy Measurements of Ba(Fe_{0.96}Co_{0.04})_2As_2 Single Crystals

80%
Szabó P., Girovský J., Pribulová Z., Samuely T., Bud'ko S., Canfield P., Samuely P.
Acta Physica Polonica A
|
2010
|
vol. 118
|
issue 5
1045-1046
EN
Point contact spectroscopy results are presented on the electron underdoped Ba(Fe_{0.96}Co_{0.04})_2As_2 single crystals. Two superconducting energy gaps with coupling values 2 Δ_1 ∿ kT_{c} ≈ 2.55 and 2 Δ_2 ∿ kT_{c} ≈ 11 at T_{c} = 15.5 K have been observed in the point contact spectra. The temperature dependence of the normal state background of the point contact spectra observed between T_{c} and T_{N} indicates antiferromagnetic origin of the V-shaped minimum at zero bias.
18
Content available remote

Strong-Coupling Features in YB_6 and ZrB_{12} Studied by Point-Contact Spectroscopy

80%
Girovský J., Szabó P., Mori T., Samuely P.
Acta Physica Polonica A
|
2010
|
vol. 118
|
issue 5
1042-1044
EN
Point-contact spectroscopy studies of the superconducting energy gap and the electron-phonon coupling mechanism are performed on the boron rich YB_6 and ZrB_{12} single crystals. The obtained values of the superconducting energy gaps suggest the strong coupling with 2 Δ/k_{B}T_{c}≈ 4.2 for YB_6 and 2 Δ/k_{B}T_{c}≈ 4.15 for ZrB_{12}. We have observed the dominant soft phonon modes mediating superconductivity in the both samples at energy ≈ 8 meV for YB_6 and ≈ 11 meV in ZrB_{12}, respectively.
19
Content available remote

Doping Effects of Co, Ni, and Cu in FeTe_{0.65}Se_{0.35} Single Crystals

80%
Bezusyy V., Gawryluk D., Berkowski M., Cieplak M.
Acta Physica Polonica A
|
2012
|
vol. 121
|
issue 4
816-819
EN
The resistivity, magnetoresistance, and magnetic susceptibility are measured in single crystals of FeTe_{0.65}Se_{0.35} with Cu, Ni, and Co substitutions for Fe. The crystals are grown by Bridgman's method. The resistivity measurements show that superconductivity disappears with the rate which correlates with the nominal valence of the impurity. From magnetoresistance we evaluate doping effect on the basic superconducting parameters, such as upper critical field and coherence length. We find indications that doping leads to two component superconducting behavior, possibly because of local charge depression around impurities.
20
Content available remote

Magnetic Nature of a Ni Dopant in La_{1.85}Sr_{0.15}CuO_4: Spin-Glass Behavior

80%
Malinowski A., Bezusyy V., Minikayev R., Paszkowicz W., Dziawa P., Syryanyy Y., Sawicki M.
Acta Physica Polonica A
|
2010
|
vol. 118
|
issue 2
244-248
EN
The magnetic properties of La_{1.85}Sr_{0.15}CuO_4 doped with Ni was investigated in the field up to 5 T and in the temperature range from 2 K to 400 K using both dc and ac techniques. For Ni content larger than 0.05 the system exhibits irreversibility of low-field susceptibility χ(T) below a certain temperature depending on y and a cusp at T_{g} in χ(T) measured after zero-field cooling. The decay of remnant magnetization below T_{g} with time is described by a stretched-exponential function. In accordance with scaling theory, all the χ(T) data for y = 0.50 sample taken in the vicinity of T_{g} at different fields collapse onto two separate curves when plotted as q|t|^{-β} vs. B^2 |t|^{-β - γ}, where q is the spin-glass order parameter, t = (T - T_{g})/T_{g}, and β and γ are the critical exponents. All these features taken together reveal existence of spin-glass phase below T_{g}. Variation of T_{g} with y is linear below y = 0.25 and T_{g} extrapolates to 0 K for y → 0 what strongly suggests that spin-glass phase extends into superconducting region of the phase diagram.
first rewind previous Page / 2 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.