Nuclear refrigeration properties of PrNi5

Folle, H. R.; Kubota, Minoru; Buchal, Ch.; Mueller, R. M.; Pobell, F.

doi:10.1007/bf01294426

Cited by 30 publications

(9 citation statements)

References 10 publications

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“…The precool field was limited to <6.2 T by the tolerable upper limit to the stray field at the superconducting heat switch. Typically a 24 h precool was sufficient to cool the stage to 20 mK, achieving an entropy reduction of 80% of the free spin value [32]. The superconducting heat switch was then opened and the demagnetization carried out in a series of steps.…”

Section: Resultsmentioning

confidence: 99%

A microkelvin cryogen-free experimental platform with integrated noise thermometry

Batey¹,

Casey²,

Cuthbert³

et al. 2013

New J. Phys.

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We report experimental demonstration of the feasibility of reaching temperatures below 1 mK using cryogen-free technology. Our prototype system comprises an adiabatic nuclear demagnetization stage, based on hyperfineenhanced nuclear magnetic cooling, integrated with a commercial cryogenfree dilution refrigerator and 8 T superconducting magnet. Thermometry was provided by a current-sensing noise thermometer. The minimum temperature achieved at the experimental platform was 600 µK. The platform remained below 1 mK for over 24 h, indicating a total residual heat-leak into the experimental stage of 5 nW. We discuss straightforward improvements to the design of the current prototype that are expected to lead to enhanced performance. This opens the way to widening the accessibility of temperatures in the microkelvin regime, of potential importance in the application of strongly correlated electron states in nanodevices to quantum computing.

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Section: Resultsmentioning

confidence: 99%

A microkelvin cryogen-free experimental platform with integrated noise thermometry

Batey¹,

Casey²,

Cuthbert³

et al. 2013

New J. Phys.

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“…Here, the prefactor α = N 0 I(I+1)µ 2 n g 2 n /3k B contains I, the size of the spin, g n , the g-factor, N 0 , the Avogadro number and µ n , the nuclear magneton.Bulk nuclear cooling stages have predominantly been built of copper [19], owing to its high thermal conductivity, beneficial metallurgic properties and weakly coupled nuclear spins, which allows for magnetic refrigeration of the nuclear spins down to 50 nK [21], however the weak hyperfine interaction results in a decoupling of the electron system at much higher temperatures, ∼ 100 µK. Another material, a Van Vleck paramagnet, PrNi 5 , has been used as a bulk nuclear refrigerant exploiting its interaction-enhanced heat capacity in a temperature range of T > 200 µK [22] even in dry dilution refrigerators [23].Integrating the nuclear refrigerant with the nanoelectronic device yields a direct heat transfer between the electrons and nucleiQ e−n = ακ −1 B 2 (T e /T n − 1) per mole. Here, κ is the Korringa constant, and T e , T n are the electron and nuclear spin temperatures, respectively.…”

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confidence: 99%

500 microkelvin nanoelectronics

2020

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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 B T , demanding effective refrigeration techniques for nanoscale electronic devices. Commercially available dilution refrigerators have enabled typical electron temperatures in the 10 . . . 100 mK regime, however indirect cooling of nanodevices becomes inefficient due to stray radiofrequency heating and weak thermal coupling of electrons to the device substrate. Here we report on passing the millikelvin barrier for a nanoelectronic device. Using a combination of on-chip and off-chip nuclear refrigeration, we reach an ultimate electron temperature of T e = 421 ± 35 µK measured by a Coulomb-blockade thermometer. With a hold time exceeding 85 hours below 700 µK, we provide a landmark demonstration of nanoelectronics in the microkelvin regime.Accessing the microkelvin regime [1] holds the potential of enabling the observation of novel electronic states, such as topological ordering [2], electron-nuclear ferromagnets [3,4], p-wave superconductivity [5] or non-Abelian anyons [6] in the fractional quantum Hall regime [7]. In addition, the error rate of various quantum devices, including single electron charge pumps [8] and superconducting quantum circuits [9] could improve by more effective thermalization of the charge carriers.The conventional means of cooling nanoelectronic devices relies on the thermal coupling between the refrigerator and the conduction electrons, mediated by phononphonon coupling in the insulating substrate,Q p-p ∝ T 4 p1 − T 4 p2 and electron-phonon coupling in the devicė Q e-p ∝ T 5 e − T 5 p [10, 11], both rapidly diminishing at low temperatures. In a typical dilution refrigerator, T p > 5 mK, and specially built systems reach 1.8 mK [12], which limits T e > T p to the millikelvin regime. The lowest static electron temperature reached with this technique was T e = 3.9 mK [13] in an all-metallic nanostructure, and other experiments reached similar values [14][15][16] in semiconductor heterostructures.This technological limitation can be bypassed by adia- * These authors contributed equally to this work.batic magnetic refrigeration, which relies on the constant occupation probability of the energy levels of a spin system, ∼ exp(−gµBm/k B T ) in the absence of heat exchange with the environment [17]. Here, k B T is the thermal energy at a temperature of T , gµB is the energy split between adjacent levels at a magnetic field of B and m is the spin index. Thus, the constant ratio B/T allows for controlling the temperature of the spin system by changing the magnetic field. Exploiting the spin of the nuclei [18,19], this technique has been utilized to cool bulk metals down to the temperature range of T ∼ 100 pK [20]. If only Zeeman splitting is present, which is linear in B, the ultimate tempe...

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“…b = 0.36 mT & T c = 50 nK for Cu [35 ]). The poor thermal conductivity of the material itself (comparable to that of brass at low temperatures [36 ]) also limits the ultimate temperatures of attached samples. Depending on the balance of the heat leaks and available cooling power, together with the temperature targeted, these aspects may not be significant, however the difficulty in obtaining and working with the material make its use somewhat unattractive [37 ].…”

Section: Figure 22: Entropy Of Copper Nuclei In An Externally Appliementioning

confidence: 99%