Характерною загальною особливістю електронної структури надпровід-ників на основі заліза є систематичний зсув реальних електронних зон у порівнянні з розрахованими, який, ймовірно, пов'язаний із міжелект-ронною взаємодією. У ряді недавніх робіт було висловлено гіпотезу, що цей зсув разом із величиною взаємодії мають зменшуватися зі збільшен-ням температури, а також наведено експериментальні дані на її підтрим-ку. Ми детально дослідили еволюцію електронної структури FeSe від 20 до 250 К та прийшли до висновку, що зсув із температурою d xy -зони в центрі Бріллюенової зони приводить до протилежного ефекту -енергія зв'язку d xy -електронів збільшується з ростом температури.Ключові слова: електронна спектроскопія з кутовою роздільчою здатніс-тю, електронна структура FeSe, надпровідники на основі заліза, метода кривини.A characteristic feature of the electronic structure of iron-based superconductors is the shift of experimental electronic bands in comparison to the results of calculations. This shift is most likely a result of electron-electron interaction. In some recent papers, a hypothesis that the shift, together with
The permanent levitation above the blgh-Tc superconductors can be w e d for a W -8 ed magnetic rotor on superconducting $3qp rotaying letely without etic friction. It pmvides an zzicatlon in t=cs and various branches of experimental phgsics. The posed hi@-rotational-speed etic rotor ha^ a n m E of advantages ow to s stabilization of rotation, rapid aamping of 3 a t i o n oscillations while untwisting, low-energy suspension system ca city and others. It includes two Sm-CO megnetic discs w g h magnetic moments are directed a l o rotor axis and used f o r suspension of the rotor in %SC bearings and untwistlng device with third etic disc. For untwisting the rotor an induced -etic-eld H = &cos(2mt) was used.Fig. shows experimental de dences of the m t o r consumed (1.2.3 !?inea. respectively). For investigated rotor m e t i c friction energy losses are completely excluded and rotor axis is fixed ow@ to =tic flux pinning in the bulk of HTSC. The linear dep nce of P on J (lines 1.2) wer P on wl in vacuum (1K lo-* torr) and in aFr 0-7803-0637 -6/92 $3.00 Q 1992 IEEE KC-1 1 corres nds to viscous friction of rotor in vacuum withln whole K q u e n c y under consideration: At the rotation in the air ( -3 a t o >& (u, = consumption increases extremely and P-?'$ym%)t t%3tEEi about ap arance of turbulence. On the basis of eIperimenL data (F .) within the frequenc s, where P % o", values of a Zscosity q for aLr ('k?%rr) and vacuum (IP, 1W2 torr) were estima ted theoretically as I OllOWS r) (760) = r) (lo-') = 1.8.1U4 g/S-Cm , ( 1 r 2 ) = 1,6.1V4 g/s-Cm . Thus, we can conclude that there is no essential vortex &pinning at rotation of the "perfect" rotor and the very small power consumption o wing to magnetic losses takes place. This gives the pssi l l i t y to achive 190 alrea in vacuum of 1v torr at power consmptYn ?? about? mw. It is also. shown e erimentally that rotor speed o decreases as o(t) = w(8e-L'*at free damp in agreement with quadratic dependence of P on o.%e value of T measured e rimentally allows to determine independently 7) and rotor "g.-factor (Q % 5.2.W).It should be noted that the described system gives the possibility to determine losses due to an interaction of magnetic rotor with various media and some characteristics of these media. So, energy losses of magnetic rotor interact9 with the am0 how material F 139 were also d%rmineE As was esta%%it within the fre uency range from 2000 hertz to 0 w(t)3-27.9.t 'to, is the rotor speed at which the untwls ing field being switched off) and, therefore, P % W. The power consuptions due to magnetic viscosity and vortex currents at not very high frs uencies are propertlonal hys teresis to 1 . 8 and, therefore, withln 3 & losses w ive the main contributiOon.mFo~hiEI case we obtained 1 = 1.76.1P J and Q = 4.5.1P. wdered soft References 1.Nemoshkalenko V.V., Ivanov M.A., Nikitin B.G.. Po relov Yu.G. and Kllmenko G A 1990 Solid State Conmam. P~lk~oshkalenko V.V.. Brandt E.H.. Kordmk L A . and 7 Br ---. ___ Nikitin B.C. 1996*Physfca C 170 a 1 -Theoretfcul png(aics, uoZ.VII (0...
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