Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 10: Superconductivity: Tunneling, Josephson Junctions, SQUIDs
TT 10.3: Vortrag
Montag, 23. März 2009, 14:30–14:45, HSZ 105
Laser imaging of hot spots and waves in Bi2Sr2CaCu2O8 intrinsic Josephson junctions — •S. Guénon1, M. Grünzweig1, H. B. Wang2, J. Yuan2, A. Iishi2, S. Arisawa2, T. Hatano2, T. Yamashita2, D. Koelle1, and R. Kleiner1 — 1Physikalisches Institut & Center for CollectiveQuantum Phenomena, Universität Tübingen, Germany — 2National Institute for Materials Science, Tsukuba3050047, Japan
Motivated by the discovery of coherent Terahertz emission in large sized stacks of Bi2Sr2CaCu2O8 intrinsic Josephson junctions [1] we used low-temperature scanning laser microscopy (LTSLM) to image local electric field distributions of mesa structures patterned on top of Bi2Sr2CaCu2O8 single crystals [2]. In LTSLM a laser beam at position (x,y) on the sample surface locally warms up an area of about a few µm2. This locally well defined heat distribution changes the electrical properties of the system, which in turn leads to a voltage change Δ V(x,y) measured globally across the sample. The mesas (330µm long and 30–70µm wide) were 1 µm thick and consisted of about 670 junctions. In the low-bias regime we find clear signatures of standing electromagnetic waves that essentially are in agreement with the THz emission data in [1]. At high bias voltages we observe the formation of a hot spot, which at some currents is accompanied by standing wave patterns interacting with the hot spot.
[1] L. Ozyuzer et al., Science 318, 1291 (2007)
[2] H. B. Wang, S. Guénon et al., submitted to Phys. Rev. Lett.;
arXiv:0807.2749v1 [cond-mat.supr-con]