부산대학교 도서관

In the present investigation (2002) the current-voltage characteristics (CVCs) of break junctions in polycrystalline $MgB_2$ samples have been studied in the temperature range $4.2 K < T < T_c$. An inelastic Cooper pair tunneling accompanied by the emission of Leggett plasmons has been found for the first time in $MgB_2$ Josephson contacts. A fine structure in the CVCs of $MgB_2$ Andreev point contacts caused by a resonant emission of Leggett plasmons has been observed for the first time. An energy of the Leggett plasmon has been estimated: $E_0$ ~ 4 meV. Distinct two-gap structures have been found in the CVCs of $MgB_2$ tunneling contacts and $MgB_2$ Andreev point contacts with 7.5 meV $< \Delta_L <$ 11 meV and 1.5 meV $< \Delta_S <$ 2.5 meV. An intrinsic tunneling effect (ITE) and intrinsic multiple Andreev reflections effect (IMARE) have been observed due to the layered structure of $MgB_2$. The obtained experimental results give a direct evidence for a two-gap superconductivity in $MgB_2$. ("V. Tarasov's Readings", November 2002, Russia, Moscow, conference proceedings.)
Comment: 20 pages (8 pages - preface, 7 pages - electron copy of the "V. Tarasov's Readings" International conference proceedings published in December 2002, 4 pages - electron layout of references and figures), 6 figures. On the occasion of 20th anniversary of the first experimental observation of the Leggett collective plasma oscillation in MgB2