DOI: 10.6084/m9.figshare.8247140
title: Dataset reporting measurements of shot noise of tunneling current in La2-xSrxCuO4/La2CuO4/La2-xSrxCuO4 (LSCO/LCO/LSCO) heterostructures

description: This dataset presents shot-noise measurements performed on LSCO-based tunnel junctions, in order to identify causes of the pseudogap associated with high-temperature superconductivity in copper oxides. The data reports measurements of shot noise of tunneling current in high-quality La2-<i>x</i>Sr<i>x</i>CuO4/La2CuO4/La2-<i>x</i>Sr<i>x</i>CuO4 (LSCO/LCO/LSCO) heterostructures fabricated using atomic-layer-by-layer molecular beam epitaxy, at four doping levels. In the study, ALL-MBE was used to synethesise trilayer LSCO/LCO/LSCO films with LSCO doping level of <i>x </i>= 0.10, 0.12, 0.14, and 0.15, with film transition temperates of 28 K, 34 K, 37 K, and 38 K. Energy dispersive x-ray spectroscopy and atomic-resolution electron-energy-loss spectroscopy were used for La, Sr, and Cu elemental mapping. From these heterostructures, fabricated tunnel junction devices were fabricated using photolithography. Precision measurements of the bias dependence of the differential conductance (<i>G </i>= d<i>I</i>/d<i>V</i>, where <i>I </i>is the current and <i>V </i>is the voltage bias) were then performed using standard lock-in techniques. Two tunnel junctions were measured at each LSCO doping level in the top and bottom superconducting electrodes. The dataset consists of a single compressed <b>.rar</b> archive, with eight subdirectories. Each subdirectory includes between 800-1100 files, with the data contained in each available in both <b>.dat</b> and <b>.csv</b> format. Each subdirectory used the naming convention “lsco0pxxsn” where “xx” indicates the doping level of the La(2-x)Sr(x)CuO4 layers and n indicates either device 1 or device 2 for each doping. The data within the subdirectories is as follows: <b>lsco0p10s1</b> (doping level .10, device 1)<b>lsco0p10s2 </b>(doping level .10, device 2)<b>lsco0p12s1 </b>(doping level .12, device 1)<b>lsco0p12s2 </b>(doping level .12, device 2)<b>lsco0p14s1 </b>(doping level .14, device 1)<b>lsco0p14s2 </b>(doping level .14, device 2)<b>lsco0p15s1</b> (doping level .15, device 1)<b>lsco0p15s2 </b>(doping level .15, device 2). Each subdirectory contains four file types: <b>.dat</b> files with filenames in the format “tt.00K_xxxxV.dat”. These are the raw data from the measurements of voltage noise, labeled by the temperature tt in Kelvin, and xxxx is the dc bias voltage applied to the series combination of the sample plus 380 kOhms of series resistance. These are two-column files. The first column is the frequency bin (Hz) and the second column is the voltage noise after the cross correlation (arb units set by the voltage gain of the preamplifiers; proportional to V^2/Hz). <b>.csv</b> files which represent the same data as the .<b>dat</b> files above. <b>.dat</b> files with filenames in the format “ttK_didv4noise.dat”. These contain the measured differential conductance data associated with each temperature, needed for fitting the frequency dependence of the noise. These files are five columns. The first column is the dc bias voltage across the sample itself, in volts. The third column is the dc current through the sample in Amps. The fifth column is the differential conductance in Siemens. (The second and fourth columns are lock-in readings in arb units used to calculate the fifth column.) A single <b>.xls</b> file, containing the fit parameters obtained from the R<sub>s</sub>C<sub>p</sub> fitting analysis for each bias, with a separate sheet for each temperature. There are four columns for each temperature. Column 1 is the dc bias (in volts) applied across the series combination of the sample + 380 kOhms of series resistance. Column 2 is the fit magnitude of the voltage noise (in arb units). Column 3 is the noise magnitude converted into current noise, units of A^2/Hz, using the dI/dV at that bias. Column 4 is the R<sub>s</sub>C<sub>p</sub> fit parameter. <b>.rar</b> files can be opened using open source decompression software, for example 7-Zip. <b>.dat</b> files can be opened using text processing software. The .<b>csv</b> and .<b>xls</b> files can be opened using open source spreadsheet software such as OpenOffice Calc. <br>