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首页> 外文期刊>Physica, C. Superconductivity and its applications >Direct observation of tetrahertz electromagnetic waves emitted from intrinsic Josephson junctions in single crystalline Bi2Sr2CaCu2O8+delta
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Direct observation of tetrahertz electromagnetic waves emitted from intrinsic Josephson junctions in single crystalline Bi2Sr2CaCu2O8+delta

机译：直接观察单晶Bi2Sr2CaCu2O8 +δ中本征约瑟夫森结发出的四赫兹电磁波

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摘要

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 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.
机译：我们已经观察到由高T-c超导体Bi2Sr2CaCu2O8 +δ本征约瑟夫森结系统的单晶台面结构产生的太赫兹频率下的强烈，相干，连续和单色电磁（EM）发射。台面是通过氩离子铣削和光刻技术在Bi2Sr2CaCu2O8 +δ5单晶的劈裂表面上制成的。从样品中观察到的EM辐射的频率v遵循简单的关系：v = c / n lambda = c / l2nw和v = c2e V / hN，其中c是真空中的光速，n是a的折射率超导体，λ是真空中EM发射的波长，w是台面的宽度较短，v是施加到台面的电压，N是本征约瑟夫森结的层数，e和h是元素电荷和普朗克常数， 分别。这两个关系强烈暗示了发射的机理，首先是由于EM波对台面的几何共振，就像在台面结构中发生腔共振一样，并形成了作为腔共振模式的驻波，其次，由于ac-Josephson效应，在所有固有的Josephson交界处连贯地起作用。样品发出的功率强度的特殊温度依赖性在20至40 K的温度范围内显示出极大的最大值，这表明非平衡效应对于该系统中EM波的发射起着至关重要的作用。与以前的报告相比，估计的总功率得到了显着提高[L. Ozyuzer等人，Science 318（2007）1291，K。Kadowaki等人，Physica C 437-438（2006）111，1，E. Batov等人，应用物理来吧88（2006）262504]，并且在648 GHz频率下，w = 60 pm的单台面功率高达5μW，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台面的基本模式下制造了发射高达960 GHz的EM波的台面，而观察到的谐波高达4阶，导致频率超过2.5 THz。与以前的报告形成鲜明对比[K. Kadowaki等人，Physica C 437-438（2006）111，M.-H。 Bae等，Phys。牧师98，（2007）027002]，目前所有的测量都是在零磁场下进行的。最后，讨论了一种合理的排放机理理论模型。

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