Absence versus Presence of Dissipative Quantum Phase Transition in Josephson Junctions

Masuki, Kanta; Sudo, Hiroyuki; Oshikawa, Masaki; Ashida, Yuto

doi:10.1103/physrevlett.129.087001

Cited by 22 publications

(7 citation statements)

References 76 publications

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“…In summary, we have experimentally demonstrated through heat transport measurements that a Josephson junction acts as an inductor even in the presence of a highly resistive environment. Though the interpretation of the dissipative transition can be debated 23 , 26 , the discrepancy between the heat transport measurements and the control charge transport measurements by us here and in previous works 13 , 20 , 42 , cannot be accounted for by the existing theory and calls for further developments, both experimental and theoretical. Our findings are important not only from the fundamental physics point of view but also for future applications such as microbolometers or heat sink designs in quantum circuits.…”

Section: Resultsmentioning

confidence: 57%

“…In electrical terms, this translates to an effective phase-dependent Josephson inductance in parallel with a capacitance (see Fig. 4 c), where is an average over phase fluctuations 26 , 38 . Within this linear model, and by assuming the lumped approximation (valid since the dominant radiation wavelength λ th = h c / k B T ~ 10 cm at 150 mK is much larger than the circuit characteristic dimensions ~50 μm), the power transmission coefficient can be explicitly written 3 , 9 as τ ( ω , Φ) = 4 R S R D /∣ Z T ( ω , Φ)∣ 2 (see “Methods”), with Z T ( ω , Φ) the frequency-dependent total series impedance of the circuit.…”

Section: Resultsmentioning

confidence: 99%

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Bolometric detection of Josephson inductance in a highly resistive environment

Subero,

Maillet,

Golubev

et al. 2023

Nat Commun

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The Josephson junction is a building block of quantum circuits. Its behavior, well understood when treated as an isolated entity, is strongly affected by coupling to an electromagnetic environment. In 1983, Schmid predicted that a Josephson junction shunted by a resistance exceeding the resistance quantum RQ = h/4e2 ≈ 6.45 kΩ for Cooper pairs would become insulating since the phase fluctuations would destroy the coherent Josephson coupling. However, recent microwave measurements have questioned this interpretation. Here, we insert a small Josephson junction in a Johnson-Nyquist-type setup where it is driven by weak current noise arising from thermal fluctuations. Our heat probe minimally perturbs the junction’s equilibrium, shedding light on features not visible in charge transport. We find that the Josephson critical current completely vanishes in DC charge transport measurement, and the junction demonstrates Coulomb blockade in agreement with the theory. Surprisingly, thermal transport measurements show that the Josephson junction acts as an inductor at high frequencies, unambiguously demonstrating that a supercurrent survives despite the Coulomb blockade observed in DC measurements.

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Section: Resultsmentioning

confidence: 57%

Section: Resultsmentioning

confidence: 99%

Bolometric detection of Josephson inductance in a highly resistive environment

Subero,

Maillet,

Golubev

et al. 2023

Nat Commun

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“…26 some tentative arguments are presented, as to why the observed absence of the transition in Josephson junctions could be related to whether the normal metal bath preserves or violates phase compactness. We note that this work was not received without controversy 27,28 , and has spurred a number of follow-up works with differing results, both on the theoretical 77 and the experimental 78 side. At any rate, we expect (ii) to be important to limit the allowed forms of a generic inductive coupling to an environment for circuits involving QPS junctions.…”

Section: Resultsmentioning

confidence: 97%

Compact description of quantum phase slip junctions

Koliofoti,

Riwar

2023

npj Quantum Inf

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Quantum circuit theory is a powerful tool to describe superconducting circuits. In its language, quantum phase slips (QPSs) are considered to be the exact dual to the Josephson effect. This duality renders the integration of QPS junctions into a unified theoretical framework challenging. As we argue, different existing formalisms may be inconsistent, and the correct inclusion of time-dependent flux driving requires introducing a large number of auxiliary, nonphysical degrees of freedom. We resolve these issues by describing QPS junctions as inductive rather than capacitive elements, and reducing the Hilbert space to account for a compact superconducting phase. Our treatment provides an approach to circuit quantization exclusively in terms of node-flux-node variables, and eliminates spurious degrees of freedom. Finally, the inductive treatment reveals the possibility of a voltage-dependent renormalization of the QPS amplitude, by accounting for spatial variations of the electric field built up across the junction.

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“…As a consequence, we suggest that the performance of some high-impedance quantum devices 18 , 19 , 31 is actually improved by thermal fluctuations. It is also interesting to consider whether experimental studies of insulating behaviour in resistively shunted Josephson junctions 32 – 35 could be understood by carefully considering the role of non-zero temperature, finite-size or non-perturbative effects 36 .…”

Section: Mainmentioning

confidence: 99%

Superconductivity from a melted insulator in Josephson junction arrays

Mukhopadhyay

Senior

et al. 2023

Nat. Phys.

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Arrays of Josephson junctions are governed by a competition between superconductivity and repulsive Coulomb interactions, and are expected to exhibit diverging low-temperature resistance when interactions exceed a critical level. Here we report a study of the transport and microwave response of Josephson arrays with interactions exceeding this level. Contrary to expectations, we observe that the array resistance drops dramatically as the temperature is decreased—reminiscent of superconducting behaviour—and then saturates at low temperature. Applying a magnetic field, we eventually observe a transition to a highly resistive regime. These observations can be understood within a theoretical picture that accounts for the effect of thermal fluctuations on the insulating phase. On the basis of the agreement between experiment and theory, we suggest that apparent superconductivity in our Josephson arrays arises from melting the zero-temperature insulator.

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Absence versus Presence of Dissipative Quantum Phase Transition in Josephson Junctions

Cited by 22 publications

References 76 publications

Bolometric detection of Josephson inductance in a highly resistive environment

Bolometric detection of Josephson inductance in a highly resistive environment

Compact description of quantum phase slip junctions

Superconductivity from a melted insulator in Josephson junction arrays

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