Browsing by Author "Meschke, Matthias"
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Item Electronic cooling a submicron-sized metallic beam(2009) Muhonen, Juha; Niskanen, Antti; Meschke, Matthias; Pashkin, Yury; Tsai, J.S.; Sainiemi, L.; Franssila, S.; Pekola, Jukka; Department of Applied Physics; Department of Micro and NanosciencesWe demonstrate electronic cooling of a suspended AuPd island using superconductor-insulator-normal metal tunnel junctions. This was achieved by developing a simple fabrication method for reliably releasing narrow submicron-sized metal beams. The process is based on reactive ion etching and uses a conducting substrate to avoid charge-up damage and is compatible with, e.g., conventional e-beam lithography, shadow-angle metal deposition, and oxide tunnel junctions. The devices function well and exhibit clear cooling, up to a factor of 2 at sub-Kelvin temperatures.Item Electronic refrigeration at the quantum limit(2009-05-18) Timofeev, Andrey; Helle, Meri; Meschke, Matthias; Möttönen, Mikko; Pekola, Jukka; Department of Applied PhysicsWe demonstrate quantum-limited electronic refrigeration of a metallic island in a low-temperature microcircuit. We show that matching the impedance of the circuit enables refrigeration at a distance, of about 50 μm in our case, through superconducting leads with a cooling power determined by the quantum of thermal conductance. In a reference sample with a mismatched circuit this effect is absent. Our results are consistent with the concept of electromagnetic heat transport. We observe and analyze the crossover between electromagnetic and quasiparticle heat flux in a superconductor.Item Electronic Refrigeration at the Quantum Limit(American Physical Society (APS), 2009) Timofeev, Andrey V.; Helle, Meri; Meschke, Matthias; Möttönen, Mikko; Pekola, Jukka P.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceWe demonstrate quantum-limited electronic refrigeration of a metallic island in a low-temperature microcircuit. We show that matching the impedance of the circuit enables refrigeration at a distance, of about 50 μm in our case, through superconducting leads with a cooling power determined by the quantum of thermal conductance. In a reference sample with a mismatched circuit this effect is absent. Our results are consistent with the concept of electromagnetic heat transport. We observe and analyze the crossover between electromagnetic and quasiparticle heat flux in a superconductor.Item Heat Transistor: Demonstration of Gate-Controlled Electronic Refrigeration(American Physical Society (APS), 2007) Saira, Olli-Pentti; Meschke, Matthias; Giazotto, Francesco; Savin, Alexander M.; Möttönen, Mikko; Pekola, Jukka P.; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceWe present experiments on a superconductor–normal-metal electron refrigerator in a regime where single-electron charging effects are significant. The system functions as a heat transistor; i.e., the heat flux out from the normal-metal island can be controlled with a gate voltage. A theoretical model developed within the framework of single-electron tunneling provides a full quantitative agreement with the experiment. This work serves as the first experimental observation of Coulombic control of heat transfer and, in particular, of refrigeration in a mesoscopic system.Item Heat transistor: Demonstration of gate-controlled electronic refrigeration(2007-07-09) Saira, Olli-Pentti; Meschke, Matthias; Giazotto, Francesco; Savin, Alexander; Möttönen, Mikko; Pekola, Jukka; Department of Applied PhysicsWe present experiments on a superconductor–normal-metal electron refrigerator in a regime where single-electron charging effects are significant. The system functions as a heat transistor; i.e., the heat flux out from the normal-metal island can be controlled with a gate voltage. A theoretical model developed within the framework of single-electron tunneling provides a full quantitative agreement with the experiment. This work serves as the first experimental observation of Coulombic control of heat transfer and, in particular, of refrigeration in a mesoscopic system.Item Origin of hysteresis in proximity Josephson junction(2008-08-08) Courtois, H; Meschke, Matthias; Peltonen, Joonas; Pekola, Jukka; Department of Applied PhysicsWe investigate hysteresis in the transport properties of superconductor–normal-metal–superconductor (S-N-S) junctions at low temperatures by measuring directly the electron temperature in the normal metal. Our results demonstrate unambiguously that the hysteresis results from an increase of the normal-metal electron temperature once the junction switches to the resistive state. In our geometry, the electron temperature increase is governed by the thermal resistance of the superconducting electrodes of the junction.Item Primary tunnel junction thermometry(2008-11-14) Pekola, Jukka; Holmqvist, Tommy; Meschke, Matthias; Department of Applied PhysicsWe describe the concept and experimental demonstration of primary thermometry based on a four-probe measurement of a single tunnel junction embedded within four arrays of junctions. We show that in this configuration random sample specific and environment-related errors can be avoided. This method relates temperature directly to Boltzmann constant, which will form the basis of the definition of temperature and realization of official temperature scales in the future.Item Primary Tunnel Junction Thermometry(American Physical Society (APS), 2008) Pekola, Jukka P.; Holmqvist, Tommy; Meschke, Matthias; Department of Applied Physics; Teknillisen fysiikan laitos; Perustieteiden korkeakoulu; School of ScienceWe describe the concept and experimental demonstration of primary thermometry based on a four-probe measurement of a single tunnel junction embedded within four arrays of junctions. We show that in this configuration random sample specific and environment-related errors can be avoided. This method relates temperature directly to Boltzmann constant, which will form the basis of the definition of temperature and realization of official temperature scales in the future.Item Recombination-limited energy relaxation in a Bardeen-Cooper-Schrieffer superconductor(2009-07-01) Timofeev, Andrey; García, Ćsar Pascual; Kopnin, Nikolai; Savin, Alexander; Meschke, Matthias; Giazotto, Fransesco; Pekola, Jukka; Department of Applied PhysicsWe study quasiparticle energy relaxation at subkelvin temperatures by injecting hot electrons into an Al island and measuring the energy flux from quasiparticles into phonons both in the superconducting and in the normal state. The data show strong reduction of the flux at low temperatures in the superconducting state, in qualitative agreement with the theory for clean superconductors. However, quantitatively the energy flux exceeds the theoretical predictions both in the superconducting and in the normal state, suggesting an enhanced or additional relaxation process.Item Setup for Small Scale Nuclear Demagnetisation Refrigerator(2016-06-07) Muhojoki, Jesse; Meschke, Matthias; Perustieteiden korkeakoulu; Pekola, JukkaItem Single-Electronic Radio-Frequency Refrigerator(2009-09-17) Kafanov, Sergey; Kemppinen, Antti; Yu, A.; Pashkin, M.; Meschke, Matthias; Tsai, J.S; Pekola, Jukka P.; Department of Applied PhysicsWe demonstrate experimentally that a hybrid single-electron transistor with superconducting leads and a normal-metal island can be refrigerated by an alternating voltage applied to the gate electrode. The simultaneous measurement of the dc current induced by the rf gate through the device at a small bias voltage serves as an in situ thermometer.Item Thermal conductance by the inverse proximity effects in a superconductor(2010-08-27) Peltonen, Joonas; Virtanen, Pauli; Meschke, Matthias; Koski, J.V.; Heikkilä, Tero; Pekola, Jukka; Department of Applied PhysicsWe study heat transport in hybrid lateral normal-metal–superconductor–normal-metal structures. We find the thermal conductance of a short superconducting wire to be strongly enhanced beyond the BCS value due to the inverse proximity effect, resulting from contributions of elastic cotunneling and crossed Andreev reflection of quasiparticles. Our measurements agree with a model based on the quasiclassical theory of inhomogeneous superconductivity in the diffusive limit.Item Wideband detection of the third moment of shot noise by a hysteretic Josephson junction(2007-05-16) Timofeev, A.V.; Meschke, Matthias; Peltonen, Joonas; Heikkilä, Tero; Pekola, Jukka; Department of Applied PhysicsWe use a hysteretic Josephson junction as an on-chip detector of the third moment of shot noise of a tunnel junction. The detectable bandwidth is determined by the plasma frequency of the detector, which is about 50 GHz in the present experiment. The third moment of shot noise results in a measurable change of the switching rate when reversing polarity of the current through the noise source. We analyze the observed asymmetry assuming adiabatic response of the detector.
