Observation of hotspot in BSCCO thin film structure by fluorescent thermal imaging

Local SiC photoluminescence evidence of hot spot formation and sub-THz coherent emission from a rectangularBi2Sr2CaCu2O8Minami1, Watanabe2, Sato3 et al. 2014Phys. Rev. B668501View full textAdd to dashboardCite

“…Application of a dc current I to a superconductor can result in extreme spatial variations in the local temperature T (r) known as hot spots [1][2][3][4][5][6][7][8][9][10][11][12]. A hot spot was first inferred from the observed hysteresis in the current-voltage I -V characteristics (IVCs) of low transition temperature T c superconducting microbridges [1].…”

“…It * minami@bk.tsukuba.ac.jp † Present address: Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan; ksato1014@icloud.com ‡ Present address: Wide Bandgap Materials Group, Optical and Electronic Materials Unit, Environment and Energy Materials Division, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; YAMAMOTO.Takashi@nims.go.jp involves covering the sample with a thin polymer film containing rare-earth complexes, exciting the complexes with ultraviolet (UV) light, and measuring their resulting T -dependent photoluminescence (PL). By applying this technique to thin films of YBCO and the high-T c superconductor Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212), the photoluminescence of the covering polymer film provided detailed maps of the hot spot T (r) in the superconducting film without any scanning distortions, because this technique allows for a direct measurement of T (r) [9][10][11][12]. However, even such measurements can include T (r) distortions caused by multiple light reflections from parallel regions of the polymer film surface and variable fluorescence efficiencies arising from regions of nonuniform polymer film thickness, especially at the sample's corners and edges [9].…”

Generation of electromagnetic waves from 0.3 to 1.6 terahertz with a high-Tc superconducting Bi2Sr2CaCu2O8+δ intrinsic Josephson junction emitter

“…52 An important issue for high P generation from the IJJ-THz emitter is how to minimize the Joule heating effects due to the dc bias current I. From the low temperature scanning laser microscopy technique, 5-7 the direct temperature distribution T(r) measurements of mesas by using photoluminescence techniques, [24][25][26][27] and the numerical simulations, 43,44 the Joule heating was often found to cause severely inhomogeneous T(r) in the mesa, including hot spots with T(r) > T c , greatly reducing P. Such heating effects reduce the hysteresis area of the currentvoltage (I-V) characteristics (IVCs), and lead to a discontinuous drop in V in the lower I bias region of the outer IVC branch.…”

Influence of the local heating position on the terahertz emission power from high-Tc superconducting Bi2Sr2CaCu2O8+δ mesas

“…6 Since P / N 2 , increasing N could, in principle, enhance P greatly. [7][8][9] However, in practice, thicker mesas lead to considerably larger Joule heating, which can drive the local mesa temperature T(r) above T c in a region known as a "hot spot," [10][11][12][13] greatly limiting the emission P. Indeed, enormously inhomogeneous T(r) distributions in a mesa were observed by low temperature scanning laser microscopy (LTSLM) [14][15][16] and by photoluminescence (PL) techniques, 17,18 and were predicted by numerical simulations. 19,20 More recently, by directly measuring the mesa T(r) using the photoluminescence of attached SiC microcrystals during simultaneous spectroscopical investigations of the THz radiation from the Bi2212 devices, we also confirmed the formation of a hot spot in the higher current I bias region of the I-V characteristics (IVCs).…”