An Electronic Primary Thermometer Based on Thermal Shot Noise

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An Electronic Primary Thermometer Based on
Thermal Shot Noise

• Lafe Spietz, K.W. Lehnert, Irfan Siddiqi,
• R.J. Schoelkopf
• Department Of Applied Physics, Yale University
• Thanks to
• Michel Devoret and Dan Prober

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Introduction

• Thermal-shot noise in tunnel junctions
  a voltage-dependent combination of Johnson
  noise and shot noise
• Relates T and V using only e and kB
• Demonstration of functional form for tunnel
  junction T800 mK to gt10 K

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Fundamental Noise Sources

• Johnson-Nyquist Noise
• Frequency-independent
• Temperature-dependent
• Used for thermometry

Shot Noise

• Frequency-independent
• Temperature independent

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Conduction in Tunnel Junctions
M I M
Difference gives current
Assume Tunneling amplitudes and
D.O.S. independent of Energy
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Thermal-Shot Noise of a Tunnel Junction
Sum gives noise
D. Rogovin and D.J. Scalpino, Ann Phys. 86,1
(1974)
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Thermal-Shot Noise of a Tunnel Junction
2eI Shot Noise
Transition Region eVkBT
4kBT
Johnson Noise
R
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Tunnel Junction Dolan Bridge Fabrication
Al-AlOX-Al Junction(AFM)
Dolan Resist Bridge(SEM)
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The Measurement
For t 1 second
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Self-Calibration Technique for Thermometry
P GB( SIAmpSI(V,T) )
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Comparison of normalized data to functional form
over wide range
Normalized Data
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Merits Vs. Complications
Merits
Fast and self-calibrating Primary
Wide T range (mK to gt10K)
No B-dependence
Measures electron temperature
Possibility to relate T to frequency!

Complications
Self heating
Frequency dependence
I(V) nonlinearities from
Density of states
Barrier shape
Weak localization, etc Amplifier nonlinearity
R. J. Schoelkopf et al., Phys Rev. Lett. 80,
2437 (1998)
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Summary

• New Tunnel Junction Thermometer based on voltage
  and temperature dependent noise of a tunnel
  junction (thermal-shot noise.)
• Fast, accurate thermometer
• works over a wide temperature range
• Relates T to V using only e and kb
  implications for metrology