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1.约瑟夫森效应的历史1959年,美国物理学家加埃弗(IvarGiaever)做了一个重要的实验:他把一块超导体和一块正常导体连接在一起,中间放一块很薄的绝缘介质,这层绝缘介质对于电子来说就是一个势垒,当他在连接起来的超导体和正常导体两边加上电压后,发现电子可以穿过,他把这种现象叫做隧道效应。1960年加埃弗将两边换成超导体,仍然产生了隧道效应。但是,加埃弗的实验现象并没有引起科学界的足够重视,因为在超导研究的初期人们就已经知道,超导电流是由电子对构成的,电子对穿过绝缘层的可能性太小了。 相似文献
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In the framework of T2HDM, we calculated the new physics contributions involving neutral Higgs bosons to the branching ratios of ^-Bs,d^0→e^+e^-(e= e,μ) decays. Comparing the theoretical predictions with the experimental upper-limits, we found that (a) The data of Br(^-Bs,d^0→e^+e^-) give the upper bound on tanβ: tanβ≤22, while Br(^-Bs^0→e^+e^-) give tanβ≤12 for fixed δ = 0^0, mH+ = 350 CeV, mH^0 = 160 GeV, mh^0 = 115 GeV and mA^0 = 120 GeV; (b) A light neutral Higgs boson mass mho (mA^0) less than 50 GeV (120 GeV) is excluded by the data of branching ratios for ^-Bs,d^0→e^+e^-(e = μ) decays with tanβ= 10; (c) The bounds on mh^0 and tanβ, or mA^0 and tanβ are strongly correlated: a smaller (larger) tanβ means a lighter (heavier) neutral Higgs boson. 相似文献
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