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Effect of twin-domain topology on local dc and microwave properties of cuprate films
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View: Figures


Image of FIG. 1.
FIG. 1.

Details of the HTS resonator geometry. dc bias is applied through current leads I1 and I2 while voltage leads V1 and V2 are used as potential probes to measure global IVCs as well as LSM photoresponse in dc resistive and unbiased TEI modes. Two capacitive gaps separate the YBCO structure of the resonator from input and output rf electrodes used for microwave characterization of integral and local rf properties. The approximate area A1 of the LSM images in Fig. 3 is outlined by the dashed frame.

Image of FIG. 2.
FIG. 2.

Simplified schematic representation of the LSM experiment for simultaneous 2D visualization of optical, thermoelectric, dc, and microwave photoresponse of the tested resonator structure. Drawing is not to scale.

Image of FIG. 3.
FIG. 3.

Half-tone LSM images of (a) reflectivity map showing the twinned structure of the LAO substrate, (b) dc critical state indicating resistive regions of the YBCO strip at and , (c) room-temperature thermoelectric map illustrating the twin microstructure in YBCO, and (d) standing wave pattern of . All scan frames are acquired with a laser probe. Bright areas indicate high LSM PR under laser-beam irradiation. Area A2 is imaged further in Fig. 9.

Image of FIG. 4.
FIG. 4.

The same area LSM scans of (a) twinned topology and (b) resistive dc transport properties of YBCO strip. Positions of the strip edges are outlined by the dashed lines. A regular array of lamellar (100)-type twin domains in YBCO is clearly visible in the thermoelectric LSM image (a). Brightness modulation between adjacent parquet-like structured twin-domains results from different orientations of individual twins inside domain relative to the direction of heat transport from the laser probe. Double-end-arrow dotted white lines show schematically the positions of kinks in the underlying LAO substrate. Points P1 and P2 indicate two positions of the stationary laser probe used to study the local electronic properties of the sample. The semitransparent area around P2 shows the region of thermal excitation outside the laser probe.

Image of FIG. 5.
FIG. 5.

Voltage LSM response (diamonds) at point P1 (a) and global (blue solid line) resistance R(T) (b) vs temperature of the HTS resonator at . In (a) the blue solid line is the temperature derivative of R(T) shown in (b), revealing peaks at transition temperatures and . Curves “1” and “2” in (b) are reconstructions of R(T) that give rise to the global R(T) signal. In (b) the transition temperature widths are denoted as and .

Image of FIG. 6.
FIG. 6.

Current dependencies of local dc LSM PR at 88.1 K (a) and 88.5 K (b) and the corresponding reconstructed IVCs [(c) and (d)] that were measured in position P1 [see Fig. 4(a)] of the YBCO strip. indicates the local value of the critical current.

Image of FIG. 7.
FIG. 7.

The 1850 MHz resonator (Fig. 1) output spectrum at generated as a result of the NL mixing of the two primary tones and at corresponding frequencies and , centered with spacing around the third harmonic resonant frequency of the device, . The signals at frequencies and were used for the LSM imaging of both inductive and resistive components of rf PR, while the signals at and were used for imaging of NL sources. The signal at was used for LSM mapping to probe the spatial distribution of local insertion losses.

Image of FIG. 8.
FIG. 8.

Log-log plot of inductive LSM PR vs showing classic square-law dependence (a) and linear plot of the dependence on showing the local value of rf critical current density at the point P1 at 80 K.

Image of FIG. 9.
FIG. 9.

Detail LSM images of dc dissipative regions (a), resistive rf response (b), dc photoresponse due to combined dc and rf currents (c), as well as distribution of (d), thermoelectric (e) and IMD (f) properties of YBCO microstrip at the position of one of the inner corners of the patterned structure that sharply changes the direction of dc and rf current flow (area A2 in Fig. 3). The position of YBCO/LAO patterned edge is outlined by the dashed white line. White arrows in (b) and (e) show the expected positions of intertwin boundaries.

Image of FIG. 10.
FIG. 10.

reflective LSM images [(a) and (c)] and corresponding microwave PR images [(b) and (d)] showing the influence of twin-domain structure on rf transport properties of a thin YBCO film patterned edge. The inset in (a) shows the reflectivity of the YBCO in the area framed by the dashed box, and is replotted with higher contrast.

Image of FIG. 11.
FIG. 11.

Line-scan modulation of microwave LSM PR (a) along (-scan) and (b) across (-scan) the patterned YBCO/LAO edge strip in Fig. 10. The striped segments show the position of TDBs along the line scans. The influence of the twin-domain structure is clearly visible.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Effect of LaAlO3 twin-domain topology on local dc and microwave properties of cuprate films