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(Color online) Experiment layout and schematic of zero dimensional heating model. The circulator and lowpass RF filter keep the amplifier noise from heating the junction. The inset at top shows scanning electron microscope of junction, with junction highlighted in green false color.
(Color online) Normalized noise plots. The vertical axis is normalized to zero frequency equilibrium noise and the horizontal axis is normalized to . The rise is the zero-bias noise as temperature gets lower comes from the finite frequency of the measurement.
(Color online) Comparison of SNT temperature to ruthenium oxide temperature. Deviation of zero frequency model shows the effect of finite measurement frequency. The horizontal error bars show calibration uncertainty of ruthenium oxide thermometer, the vertical error bars show statistical uncertainty in SNT measurement, and the dotted line shows theoretical estimate of deviation of naive zero frequency temperature fit from correct fit.
(Color online) Comparison of thermometer time series. SNT temperature tracks the ruthenium oxide temperature, with different time constants because they are on different parts of the cryostat. Bottom illustration depicts our one-dimensional heating model. Wiedemann-Franz thermal conductance scales with temperature, as does the required bias voltage to make a temperature determination, and so the fractional temperature deviation remains constant. The lead resistance in SNT junctions is typically less than a part in a thousand of the junction resistances, making this a very small effect.
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