Spectral Features of Terahertz Wave Emitting Bi2Sr2CaCu2O8+δ Mesas and Recent Results
Lutfi Ozyuzera,*, Y. Simsekb, H. Koseoglua, F. Turkoglua, Y. Demirhana,
C. Kurterc, U. Welpc, K. E. Grayc,A. E. Koshelevc, T. Yamamotod, K. Kadowakid
Y. Kovalb, P. Mullerband H.B. Wange
aDepartment of Physics, Izmir Institute of Technology, Urla, 35430, Izmir,Turkey
bPhysics Institute III, University of Erlangen,Erlangen, Germany
cMaterials Science Division, Argonne National Laboratory, Illinois, USA
d University of Tsukuba, Tsukuba, Japan
eNational Institute for Materials Science, Tsukuba, Japan
*Corresponding author
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Phone: +90-232-7507705, Fax: +90-232-7507707
[keywords] Intrinsic Josephson Junctions, terahertz waves.
Josephson junctions are the simplest voltage to high frequency converters which can be used as a solid state source of terahertz (THz) radiation. Furthermore, intrinsic Josephson junctions, natural stacks of Josephson junctions [1], in Bi2Sr2CaCu2O8+d (Bi2212) single crystals can emit powerful THz waves, if the synchronization establishes between superconducting layers. Although three years passed after the observation of first far field THz emission [2], there is no consensus on mechanism ofsynchronization. This might be due to limited number of THz emitting mesas and data obtained from various crystals. It is still not unclear whether crystal quality or certain fabrication method influences the THz emission ability of mesas, we will discuss properties of THz emitting mesas in this presentation. Large area mesas ranging from 300x100 to 300x30 um with various heights were formed on Bi2212 single crystals obtained from various groups. Current-voltage (I-V) and THz emission characteristics were acquired at various temperatures. We have already shown that the THz emitting mesasare below a certain underdoped level, which has relativelysmall critical current in contrast to optimally doped andoverdoped Bi2212 [3]. Therefore, large area mesas fabricatedfrom underdoped crystals cause less heating and backbendingtakes place after the cavity resonance in voltage scale. We will present that detailed examination of I-V curves also reveals messenger bumps in return branch just before the THz emission. These spectral features are more robust in low frequency mesas. Furthermore, the spectral features in I-V curves were investigated to find a correlation between emission frequency and feature energy. Recent THz experiments on mesas with various geometries and fabrication techniques will also be discussed.
*This research is partially supported by TUBITAK (Scientific and Technical Research Council of Turkey) project number 108T238. L.O. acknowledges support from Turkish Academy of Sciences and Alexander von Humboldt Foundation.
References
[1] R. Kleiner and P. Müller, Phys. Rev. B 49, 1327 (1994).
[2] L. Ozyuzer et al, Science 318, 1291 (2007).
[3] L. Ozyuzer et al, Supercond. Sci. Technol. 22, 114009(2009).
[ ] talk [ ] poster
International Conference on Reactor Physics, Nuclear Power: A Sustainable Resource, Interlaken, 2008 / 1/2