We demonstrate significant cooling of electrons in a nanostructure below 10 mK by demagnetisation of thin-film copper on a silicon chip. Our approach overcomes the typical bottleneck of weak electron-phonon scattering by coupling the electrons directly to a bath of refrigerated nuclei, rather than cooling via phonons in the host lattice. Consequently, weak electron-phonon scattering becomes an advantage. It allows the electrons to be cooled for an experimentally useful period of time to temperatures colder than the dilution refrigerator platform, the incoming electrical connections, and the host lattice. There are efforts worldwide to reach sub-millikelvin electron temperatures in nanostructures to study coherent electronic phenomena and improve the operation of nanoelectronic devices. On-chip magnetic cooling is a promising approach to meet this challenge. The method can be used to reach low, local electron temperatures in other nanostructures, obviating the need to adapt traditional, large demagnetisation stages. We demonstrate the technique by applying it to a nanoelectronic primary thermometer that measures its internal electron temperature. Using an optimised demagnetisation process, we demonstrate cooling of the on-chip electrons from 9 mK to below 5 mK for over 1000 seconds.
Here we review recent progress in cooling micro/nanoelectronic devices significantly below 10 mK. A number of groups worldwide are working to produce sub-millikelvin on-chip electron temperatures, motivated by the possibility of observing new physical effects and improving the performance of quantum technologies, sensors and metrological standards. The challenge is a longstanding one, with the lowest reported on-chip electron temperature having remained around 4 mK for more than 15 years. This is despite the fact that microkelvin temperatures have been accessible in bulk materials since the mi…
We report the cooling of electrons in nanoelectronic Coulomb blockade thermometers below 4 mK. Above 7 mK the devices are in good thermal contact with the environment, well isolated from electrical noise, and not susceptible to self-heating. This is attributed to an optimised design that incorporates cooling fins with a high electron-phonon coupling and on-chip electronic filters, combined with a low-noise electronic measurement setup. Below 7 mK the electron temperature is seen to diverge from the ambient temperature. By immersing a Coulomb Blockade Thermometer in the 3He/4He refrigerant of a…
Cooling nanoelectronic devices below 10 mK is a great challenge since thermal conductivities become very small, thus creating a pronounced sensitivity to heat leaks. Here, we overcome these difficulties by using adiabatic demagnetization of \emph{both} the electronic leads \emph{and} the large metallic islands of a Coulomb blockade thermometer. This reduces the external heat leak through the leads and also provides on-chip refrigeration, together cooling the thermometer down to 2.8$\pm$0.1 mK. We present a thermal model which gives a good qualitative account and suggests that the main limitati…
The frontiers of quantum electronics have been linked to the discovery of new refrigeration methods since the discovery of superconductivity at a temperature around $4\,$K, enabled by the liquefaction of helium. Since then, the advances in cryogenics led to discoveries such as the quantum Hall effect and new technologies like superconducting and semiconductor quantum bits. Presently, nanoelectronic devices typically reach electron temperatures around $10\,$mK to $100\,$mK by commercially available dilution refrigerators. However, cooling electrons via the encompassing lattice vibrations, or ph…
We present a parallel network of 16 demagnetization refrigerators mounted on a cryofree dilution refrigerator aimed to cool nanoelectronic devices to sub-millikelvin temperatures. To measure the refrigerator temperature, the thermal motion of electrons in a Ag wire -- thermalized by a spot-weld to one of the Cu nuclear refrigerators -- is inductively picked-up by a superconducting gradiometer and amplified by a SQUID mounted at 4 K. The noise thermometer as well as other thermometers are used to characterize the performance of the system, finding magnetic field independent heat-leaks of a few …
Fragile quantum effects such as single electron charging in quantum dots or macroscopic coherent tunneling in superconducting junctions are the basis of modern quantum technologies. These phenomena can only be observed in devices where the characteristic spacing between energy levels exceeds the thermal energy, $k_\textrm{B}T$, demanding effective refrigeration techniques for nanoscale electronic devices. Commercially available dilution refrigerators have enabled typical electron temperatures in the $10$ to $100\,$mK regime, however indirect cooling of nanodevices becomes inefficient due to st…
The Peltier effect is the reverse phenomenon of the Seebeck effect, and has been observed experimentally in nanoscale junctions. However, despite its promising applications in local cooling of nanoelectronic devices, the role of strong electron correlations on such a phenomenon is still unclear. Here, by analyzing the thermoelectric properties of quantum impurity systems out of equilibrium, we unveil the essential role of electron-electron interactions and quantum resonant states in Peltier cooling, leading to the prediction of the Kondo cooling phenomenon. The existence of such Kondo cooling …
Astronomical observations of cosmic sources in the far-infrared and X-ray bands require extreme sensitivity. The most sensitive detectors are cryogenic bolometers and calorimeters operating typically at about 100 mK. The last stage of cooling (from 300 mK to 100 mK) often poses significant difficulties in space-borne experiments, both in system complexity and reliability. We address the possibility of using refrigeration based on normal metal/insulator/superconductor (NIS) tunnel junctions as the last stage cooler for cryogenic thermal detectors. We compare two possible schemes: the direct coo…
We demonstrate the possiblity to cool nanoelectronic systems in nonequilibrium situations by increasing the temperature of the environment. Such cooling by heating is possible for a variety of experimental conditions where the relevant transport-induced excitation processes become quenched and deexcitation processes are enhanced upon an increase of temperature. The phenomenon turns out to be robust with respect to all relevant parameters. It is especially pronounced for higher bias voltages and weak to moderate coupling. Our findings have implications for open quantum systems in general, where…
Heat management and refrigeration are key concepts for nanoscale devices operating at cryogenic temperatures. The design of an on-chip mesoscopic refrigerator that works thanks to the input heat is presented, thus realizing a solid state implementation of the concept of cooling by heating. The system consists of a circuit featuring a thermoelectric element based on a ferromagnetic insulator-superconductor tunnel junction (N-FI-S) and a series of two normal metal-superconductor tunnel junctions (SINIS). The N-FI-S element converts the incoming heat in a thermovoltage, which is applied to the SI…
Single-electron effects have been widely investigated as a typical physical phenomenon in nanoelectronics. The single-electron effect caused by trap sites has been observed in many devices. In general, traps are randomly distributed and not controllable; therefore, different current--voltage characteristics are observed through traps even in silicon transistors having the same device parameters (e.g., gate length). This allows us to use single-electron effects as fingerprints of chips. In this study, we analyze the single-electron effect of traps in conventional silicon transistors and show th…
Engineering of cooling mechanism is of primary importance for the development of nanoelectronics. Whereas radiation cooling is rather inefficient in nowadays electronic devices, the strong anisotropy of 2D materials allows for enhanced efficiency because their hyperbolic electromagnetic dispersion near phonon resonances allows them to sustain much larger ($\sim 10^5$) number of radiating channels. In this review, we address radiation cooling in 2D materials, specifically graphene hexagonal boron nitride (hBN) heterostructures. We present the hyperbolic dispersion of electromagnetic waves due t…
Access to lower temperatures has consistently enabled scientific breakthroughs. Pushing the limits of \emph{on-chip} temperatures deep into the microkelvin regime would open the door to unprecedented quantum coherence, novel quantum states of matter, and also the discovery of unexpected phenomena. Adiabatic demagnetization is the workhorse of microkelvin cooling, requiring a dilution refrigerator precooling stage. Pulse-tube dilution refrigerators have grown enormously in popularity due to their vast experimental space and independence of helium, but their unavoidable vibrations are making mic…
We present an improved nuclear refrigerator reaching 0.3 mK, aimed at microkelvin nanoelectronic experiments, and use it to investigate metallic Coulomb blockade thermometers (CBTs) with various resistances R. The high-R devices cool to slightly lower T, consistent with better isolation from the noise environment, and exhibit electron-phonon cooling ~ T^5 and a residual heat-leak of 40 aW. In contrast, the low-R CBTs display cooling with a clearly weaker T-dependence, deviating from the electronphonon mechanism. The CBTs agree excellently with the refrigerator temperature above 20 mK and reach…
A method is described for cooling conductive channels to below ambient temperature. The thermodynamic induction principle dictates that the electrically biased channel will cool if the electrical conductance decreases with temperature. The extent of this cooling is calculated in detail for both case of ballistic and conventional transport with specific calculations for carbon nanotubes and conventional metals, followed by discussions for semiconductors, graphene, and metal-insulator transition systems. A theorem is established for ballistic transport stating that net cooling is not possible. F…
Engineering of cooling mechanisms is a bottleneck in nanoelectronics. Whereas thermal exchanges in diffusive graphene are mostly driven by defect assisted acoustic phonon scattering, the case of high-mobility graphene on hexagonal Boron Nitride (hBN) is radically different with a prominent contribution of remote phonons from the substrate. A bi-layer graphene on hBN transistor with local gate is driven in a regime where almost perfect current saturation is achieved by compensation of the decrease of the carrier density and Zener-Klein tunneling (ZKT) at high bias. Using noise thermometry, we s…
Silicon spin qubits promise to leverage the extraordinary progress in silicon nanoelectronic device fabrication over the past half century to deliver large-scale quantum processors. Despite the scalability advantage of using silicon technology, realising a quantum computer with the millions of qubits required to run some of the most demanding quantum algorithms poses several outstanding challenges, including how to control so many qubits simultaneously. Recently, compact 3D microwave dielectric resonators were proposed as a way to deliver the magnetic fields for spin qubit control across an en…
Two-dimensional electron gases (2DEGs) with high mobility, engineered in semiconductor heterostructures host a variety of ordered phases arising from strong correlations, which emerge at sufficiently low temperatures. The 2DEG can be further controlled by surface gates to create quasi-one dimensional systems, with potential spintronic applications. Here we address the long-standing challenge of cooling such electrons to below 1$\,$mK, potentially important for identification of topological phases and spin correlated states. The 2DEG device was immersed in liquid $^3$He, cooled by the nuclear a…
The fabrication and operation of V-based superconducting nanorefrigerators is reported. Specifically, electrons in an Al island are cooled thanks to hot-quasiparticle extraction provided by tunnel-coupled V electrodes. Electronic temperature reduction down to 400 mK starting from 1 K is demonstrated with a cooling power ~20 pW at 1 K for a junction area of 0.3 micron^2. The present architecture extends to higher temperatures refrigeration based on tunneling between superconductors and paves the way to the implementation of a multi-stage on-chip cooling scheme operating from above 1 K down to t…
The century-old study of photon-phonon coupling has seen a remarkable revival in the past decade. Driven by early observations of dynamical back-action, the field progressed to ground-state cooling and the counting of individual phonons. A recent branch investigates the potential of traveling-wave, optically broadband photon-phonon interaction in silicon circuits. Here, we report continuous-wave Brillouin gain exceeding the optical losses in a series of suspended silicon beams, a step towards selective on-chip amplifiers. We obtain efficiencies up to $10^{4} \, \text{W}^{-1}\text{m}^{-1}$, the…
On-chip actuation and readout of mechanical motion is key to characterize mechanical resonators and exploit them for new applications. We capacitively couple a silicon nitride membrane to an off resonant radio-frequency cavity formed by a lumped element circuit. Despite a low cavity quality factor (Q$_\mathrm{E}\approx$ 7.4) and off resonant, room temperature operation, we are able to parametrize several mechanical modes and estimate their optomechanical coupling strengths. This enables real-time measurements of the membrane's driven motion and fast characterization without requiring a superco…
We study the implementation of quantum state transfer protocols in phonon networks, where in analogy to optical networks, quantum information is transmitted through propagating phonons in extended mechanical resonator arrays or phonon waveguides. We describe how the problem of a non-vanishing thermal occupation of the phononic quantum channel can be overcome by implementing optomechanical multi- and continuous mode cooling schemes to create a 'cold' frequency window for transmitting quantum states. In addition, we discuss the implementation of phonon circulators and switchable phonon routers, …
A crucial requirement for the realisation of efficient and scalable on-chip quantum communication is an ultrafast polarised single photon source operating beyond the Peltier cooling barrier of 200 K. While a few systems based on different materials and device structures have achieved single photon generation above this threshold, there has been no report of single quantum emitters with deterministic polarisation properties at the same high temperature conditions. Here, we report the first device to simultaneously achieve single photon emission with a g(2)(0) of only 0.21, a high polarisation d…
Feasibility study of continuous electronic Pomeranchuk cooling with a flavor-degenerate Wigner crystal
RWTH Aachen University（亚琛工业大学）；JARA Fundamentals of Future Information Technology（JARA未来信息技术基础）；nd Institute of Physics, RWTH Aachen University（亚琛工业大学第二物理研究所）；HFML-FELIX（荷兰强磁场实验室FELIX中心）；Radboud University（拉德堡德大学）；Max Planck Institute for the Structure and Dynamics of Matter（马普物质结构与动力学研究所）；Center for Free Electron Laser Science（自由电子激光科学中心）；University of Hamburg（汉堡大学）；I. Institute for Theoretical Physics, University of Hamburg（汉堡大学第一理论物理研究所）；Institute for Theoretical Physics and Astrophysics, University of Würzburg（维尔茨堡大学理论与天体物理研究所）；Peter Grünberg Institute (PGI-9), Forschungszentrum Jülich（于利希研究中心彼得·格林贝格研究所（PGI-9））
We propose a solid state refrigeration technique based on repeated adiabatic magnetization/demagnetization cycles of a superconductor which acts as the working substance. The gradual cooling down of a substrate (normal metal) in contact with the working substance is demonstrated for different initial temperatures of the substrate. Excess heat is given to a hot large-gap superconductor. The on-chip refrigerator works in a cyclic manner because of an effective thermal switching mechanism: Heat transport between N/N versus N/S junctions is asymmetric because of the appearance of the energy gap. T…
Transmission electron beams (TEBs) have long been used to study and manipulate materials at nanometer scales. In the late 1970's, Cherns demonstrated surface pitting in Au films upon exposure to a 1MeV TEB and observed crystal dislocations in quartz. Soon after, electron beam irradiation was used to drill nanoholes and lines in NaCl crystals, alumina sheets, CaF2 and MgO. More recent examples include the drilling of nanoholes in silicon, stainless steel, and in Si3N4 and SiO2 membranes. In this Letter we demonstrate a new and highly flexible application of TEB-based fabrication to produce intr…
Demonstration of a scalable all-solid-state refrigerator exploiting diffusion geometries and limiting interfacial conductances at temperatures below 1 kelvin
