Transcript PICO-group
PICO-group SAB presentation, Nov 9, 2006, Jukka Pekola Dr. Alexander Savin senior scientist Dr. Matthias Meschke research scientist Dr. Juha Vartiainen post doc researcher Andrey Timofeev graduate student Tommy Holmqvist graduate student Antti Kemppinen graduate student (MIKES) Olli-Pentti Saira diploma student Kurt Baarman (part time) Dr. Mikko Möttönen post doc researcher (partly at the Laboratory of Physics, TKK) Laura MacDonald (part time) Joonas Peltonen (part time) Main activities in 2005 - 06 Thermal effects and thermodynamics on a chip Josephson junction detector of noise and FCS [poster by Andrey Timofeev, presentation by Tero Heikkilä, poster by Teemu Ojanen] Cooper pair pumping and Berry phase [partly covered in the presentation of Antti Manninen] High resolution superconducting single flux quantum comparators for sub kelvin temperatures [VTT presentation/poster] Electron system Electrical environment Lattice Heat transported between two resistors Radiative contribution to net heat flow between electrons of 1 and 2: Impedance matching (= channel transmission): Linear response for small temperature difference DT = Te1 – Te2: Quantized heat conduction J. Pendry (1983), ”Quantum limits to the flow of information and entropy”: single channel heat conduction limited by GQ (phonons, photons, any carriers) K. Schwab et al. (2000), experiment with phonons D.R. Schmidt et al. (2004), predictions for photon coupling O. Chiatti et al. (2006), measurement with electrons in a 1D wire Experimental set-up x x R2 R1 x x 10 µm LJ CJ Experimental results 170 T0 = 167mK 165 Te1 (mK) 160 155 157mK 125 118mK 120 115 x x R2 R1 x x 105mK 110 105 100 75mK 60mK 95 90 (a.u.) LJ CJ Research topics for 2007 - 2009 Thermal effects: Influence of Coulomb blockade on electron cooling (2007) Cyclic electronic refrigerator (2007 - 08) Cooling by thermal noise (2007 – 09) Quantized thermal conductance by photons over mm distances (2008 – 09) Noise and full counting statistics using a Josephson junction detector: Asymmetry of shot noise of a tunnel junction at high frequencies, comparison to theories (2007) Noise spectroscopy at 1 - 100 GHz frequencies (2007 – 08) Higher moments of other mesoscopic noise sources (2008 – 09) Pumping of Cooper pairs: Measurement of Berry phase using a Josephson junction detector (2007 – 08) Towards the quantum triangle; improvement of the accuracy of a Cooper pair pump (- 2009) Coulomb Blockade Thermometer to realize LT temperature scale Cyclic cooler whose operation is based on Coulomb blockade and energy filtering in tunneling Cooling out of noise? SNIS: cooling of N by a hot resistor 1.0 kBTN = EC = 0.05D 0.8 QN / QN,opt Heat flows from hot to cold by photon radiation . . 0.6 0.4 0.2 0.0 0 2 4 6 Te / TN 8 10 Research topics for 2007 - 2009 Thermal effects: Influence of Coulomb blockade on electron cooling (2007) Cyclic electronic refrigerator (2007 - 08) Cooling by thermal noise (2007 – 09) Quantized thermal conductance by photons over mm distances (2008 – 09) Noise and full counting statistics using a Josephson junction detector: Asymmetry of shot noise of a tunnel junction at high frequencies, comparison to theories (2007) Noise spectroscopy at 1 - 100 GHz frequencies (2007 – 08) Higher moments of other mesoscopic noise sources (2008 – 09) Pumping of Cooper pairs: Measurement of Berry phase using a Josephson junction detector (2007 – 08) Towards the quantum triangle; improvement of the accuracy of a Cooper pair pump (- 2009) Coulomb Blockade Thermometer to realize LT temperature scale Implications of the presented effect Previously good thermal isolation at low T has been taken for granted (vanishing electron-phonon rate, superconductivity,...) Increased heat load and noise of microbolometers and calorimeters A way to tune thermal coupling (heat switches, optimization of bolometers) Another channel to remove heat from dissipative elements, like shunt resistors of SQUIDs at low T Acts as a mediator of increased decoherence?