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EFFECTS OF DIMENSIONAL QUANTIZATION IN THE SPECTRA OF ELECTRON-POSITRON ANNIHILATION OF NANOLAYER MONOCRYSTAL HIGH-TEMPERATURE SUPERCONDUCTIVE MATERIALS
|Adkhamjon A. Paiziev|
Institutie of Electronics, F.Khodjaeva str.33, Tashkent 700143, Uzbekistan
Monocrystal high-temperature superconductors (HTSC) with stratified structure are suitable objects for the investigation of effects of dimensional quantization, because in this case there is no necessity in the preparing of monolayer specimens, homogeneous by thickness, for providing total positron absorption in the HTSC layer. In present paper the possibility of detection of quantum dimensional effects (QDE) in monocrystal HTSC is theoretically shown for the first time. It has been established, that the spectrum of angular distribution of annihilation photons (ADAP) for monocrystal HTSC with stratified structure has strongly anisotropic character, namely, when the axis of the detection system of the installation for ADAP measurements is perpendicular to the projection of total photon pulse on the chosen z-direction in pulse space (R1), the ADAP curve has pronounced step-like character in the range of pulses which corresponds to the positions of occupied electron sub-bands. The charge states of Cu(1) atoms in superconductive chains are considered on the example of Y-Ba-Cu-O oxide and experimental results of the positron probing of core d-electrons at the HTSC is discussed. For this particular case, when the projection of total photons pulse is oriented along the conductive layer, ADAP curve is similar to the inverted parabola(R2). It has been shown, that R2 is significantly shorter than R1.It has been established that the half-width of R2 does not depend on electron characteristics of superconductive layer in HTSC. It is also necessary to take into account the influence of the substrate, as well as the decreasing of anisotropy of ADAP that both are connected with the presence of oxygen bridges in the structure of HTSC monocrystals and with disordering of separate domains.
Presentation: poster at E-MRS Fall Meeting 2004, Symposium E, by Adkhamjon A. Paiziev
See On-line Journal of E-MRS Fall Meeting 2004
Submitted: 2004-02-25 09:24 Revised: 2009-06-08 12:55