Direct observation of tetrahertz electromagnetic waves emitted from intrinsic Josephson junctions in single crystalline Bi2Sr2CaCu2O8+δ
Direct observation of tetrahertz electromagnetic waves emitted from intrinsic Josephson junctions in single crystalline Bi2Sr2CaCu2O8+δ
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DOI：
10.1016/j.physc.2007.11.090
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发表时间：
2008-04-01
影响因子：
1.7
通讯作者：
Kwok, W. -K.
中科院分区：
文献类型：
--
作者：
Kadowaki, K.;Yamaguchi, H.;Kwok, W. -K.
我们观察到高t -c超导体Bi2Sr2CaCu2O8+ δ本征约瑟夫森结系统的单晶台面结构在太赫兹频率下产生强烈的、相干的、连续的单色电磁发射。采用氩离子铣削和光刻技术在Bi2Sr2CaCu2O8+delta，5单晶的劈裂表面制备了该平台。频率,v,电磁辐射观测到的样本服从简单的关系:v = c / nλ= c / l2nw和v = c2e v / hN,其中c是光在真空速度,n超导体的折射率,λ在真空电磁发射的波长,w的短宽台面,v电压应用于台面,n层的内在的约瑟夫森结的数量,e和h是元电荷和普朗克常数,分别。这两种关系强烈地暗示了发射的机制，首先是由于电磁波与台面的几何共振，就像发生在台面结构中的腔共振一样，形成驻波作为腔共振模式，其次是由于ac-Josephson效应，该效应在所有本征Josephson结中一致地起作用。样品发射的功率强度具有特殊的温度依赖性，在20 ~ 40 K的温度范围内具有广泛的最大值，这表明非平衡效应对该系统的电磁波发射起着重要作用。与之前的报告相比，估计的总功率有了明显的提高[L]。Ozyuzer等人，Science 318 (2007) 1291， K. Kadowaki等人，physics C 437-438 (2006) 111, 1， E. Batov等人，苹果。理论物理。leet . 88(2006) 262504]，并且在648 GHz下W = 60 pm的单台达到高达5 mu W，这使我们能够将其用于某些应用。到目前为止，我们成功地在w = 40 pm的台地中制造出了在基模下发射高达960 GHz的电磁波的台地，而观测到的高次谐波高达4阶，频率超过2.5太赫兹。与之前的报道形成鲜明对比的是[K.]王晓明，等。中国生物医学工程学报（2006）：437-438。Bae等人，物理学。[j] .光谱学通报，（2007）[027002]，目前所有的测量都是在零磁场下进行的。最后，讨论了一个合理的理论模型。(c) 2008 Elsevier B.V.版权所有
We have observed intense, coherent, continuous and monochromatic electromagnetic (EM) emission at terahertz frequencies generated from a single crystalline mesa structure of the high-T-c superconductor Bi2Sr2CaCu2O8+delta intrinsic Josephson junction system. The mesa is fabricated by the Argon-ion-milling and photolithography techniques on the cleaved surface of Bi2Sr2CaCu2O8+delta,5 single crystal. The frequency, v, of the EM radiation observed from the sample obeys simple relations: v = c/n lambda = c/l2nw and v = c2e V/hN, where c is the light velocity in vacuum, n the refractive index of a superconductor,lambda the wave length of the EM emission in vacuum, w the shorter width of the mesa, V the voltage applied to the mesa, N the number of layers of intrinsic Josephson junctions, e and h are the elementary charge and the Planck constant, respectively. These two relations strongly imply that the mechanism of the emission is, firstly, due to the geometrical resonance of EM waves to the mesa like a cavity resonance occuring in the mesa structure, and forming standing waves as cavity resonance modes, and secondly, due to the ac-Josephson effect, which works coherently in all intrinsic Josephson junctions. The peculiar temperature dependence of the power intensity emitted form samples shows a broad maximum in a temperature region between 20 and 40 K, suggesting that the nonequilibrium effect plays an essential role for the emission of EM waves in this system. The estimated total power is significantly improved in comparison with the previous report [L. Ozyuzer et al., Science 318 (2007) 1291, K. Kadowaki, et al., Physica C 437-438 (2006) 111, 1, E. Batov, et al., Appl. Phys. Lett. 88 (2006) 262504], and reached as high as 5 mu W from single mesa with w = 60 pm at 648 GHz, which enables us to use it for some of applications. So far, we succeeded in fabricating the mesa emitting EM waves up to 960 GHz in the fundamental mode in the w = 40 pm mesa, whereas the higher harmonics up to the 4-th order were observed, resulting in a frequency exceeding 2.5 THz. In sharp contrast to the previous reports [K. Kadowaki, et al., Physica C 437-438 (2006) 111, M.-H. Bae, et al., Phys. Rev. Lett. 98, (2007) 027002], all the present measurements were done in zero magnetic field. Lastly, a plausible theoretical model for the mechanism of emission is discussed. (c) 2008 Elsevier B.V. All rights reserved.