Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:cond-mat/0301467 · Physical review. B, Condensed matter

Quantum effects in small-capacitance single Josephson junctions

道生 渡部, David B. Haviland

Published Mar 17, 2003• 32 citations
arXivHTMLPDF

Abstract

We have measured the current-voltage $(I\ensuremath{-}V)$ characteristics of small-capacitance single Josephson junctions at low temperatures $(T=0.02--0.6\mathrm{K}),$ where the strength of the coupling between the single junction and the electromagnetic environment was controlled with one-dimensional arrays of dc superconducting quantum interence devices (SQUIDs). The single-junction $I\ensuremath{-}V$ curve is sensitive to the impedance of the environment, which can be tuned in situ. We have observed Coulomb blockade of Cooper-pair tunneling and even a region of negative differential resistance, where the zero-bias resistance ${R}_{0}^{\ensuremath{'}}$ of the SQUID arrays is much higher than the quantum resistance ${R}_{K}\ensuremath{\equiv}{h/e}^{2}\ensuremath{\approx}26\mathrm{k}\ensuremath{\Omega}.$ The negative differential resistance is evidence of the coherent single-Cooper-pair tunneling within the theory of current-biased single Josephson junctions. Based on this theory, we have calculated the $I\ensuremath{-}V$ curves numerically in order to compare then with the experimental ones at ${R}_{0}^{\ensuremath{'}}\ensuremath{\gg}{R}_{K}.$ The numerical calculation agrees with the experiments qualitatively. We also discuss the ${R}_{0}^{\ensuremath{'}}$ dependence of the single-Josephson-junction $I\ensuremath{-}V$ curve in terms of the superconductor-insulator transition driven by changing the coupling to the environment.

DOI
10.1103/physrevb.67.094505

Related papers

Coulomb Blockade and Coherent Single-Cooper-Pair Tunneling in Single Josephson Junctions

道生 渡部, David B. Haviland

We have measured the current-voltage characteristics of small-capacitance single Josephson junctions at low temperatures ( T< or =0.04 K), where the strength of the coupling between the single junction and the electromagnetic environment was controlled with one-dimensional arrays of dc SQUIDs. We have clearly observed Coulomb blockade of Cooper-pair tunneling and even a region of negative differential resistance, when the zero-bias resistance of the SQUID arrays is much higher than the quantum resistance h/e(2) approximately 26 kOmega. The negative differential resistance is evidence of coherent single-Cooper-pair tunneling in the single Josephson junction.

arXiv:cond-mat/0103502•Physical Review Letters•May 28, 2001•60 citations

Control of the electromagnetic environment for single Josephson junctions using arrays of dc SQUIDs

道生 渡部, David B. Haviland, Richard L. Kautz

We have measured the current–voltage characteristics of small-capacitance single Josephson junctions at low temperatures T ≤ 0.04 K, where the strength of the coupling between the single junction and the electromagnetic environment was controlled with one-dimensional arrays of dc SQUIDs. When the zero-bias resistance of the SQUID arrays is much higher than the quantum resistance h/e 2 ≈ 26 kΩ, a transition to a clear Coulomb blockade of Cooper-pair tunnelling is induced in the single junction. The measured blockade voltage agrees with the theoretical prediction.

Superconductor Science and Technology•Sep 25, 2001•6 citations

Small-Capacitance Josephson Junctions: One-Dimensional Arrays and Single Junctions

道生 渡部, David B. Haviland

We review experiments on small-capacitance Josephson junctions. When the Josephson junction is fabricated in the configuration of dc superconducting quantum interference device (SQUID), the Josephson coupling can be tuned IN SITU with an external magnetic field. The electrical transport properties of one-dimensional arrays of small-capacitance dc SQUIDs have been investigated in order to study the superconductor-insulator transition. The arrays have also been used to bias a single Josephson junction, and a clear Coulomb blockade of Cooper-pair tunneling has been observed in the single junction.

arXiv:cond-mat/0301340•Jan 20, 2003•2 citations

Quantum effects in nanoscale Josephson junction circuits

S. Corlevi

This thesis presents the results of an experimental study on single-charge effects in nanoscale Josephson junctions and Cooper pair transistors (CPTs). In nanoscale Josephson junctions the charging energy EC becomes significant at sub-Kelvin temperatures and single-charge effects, such as the Coulomb blockade of Cooper pair tunneling, influence the transport properties. In order to observe charging effects in a single Josephson junction, the impedance of the electromagnetic environment surrounding the junction has to be larger than the quantum resistance (RQ=h/4e2≈6.45kΩ). In this work the high impedance environment is obtained by biasing the sample under test (single Josephson junction or CPT) with four one-dimensional Josephson junction arrays having SQUID geometry. The advantage of this configuration is the possibility of tuning in situ the effective impedance of the electromagnetic environment. By applying a magnetic field perpendicular to the SQUID loops, the Josephson energy EJ of the SQUIDs is suppressed, resulting in an increase of the measured zero bias resistance of the arrays of several orders of magnitude (104< R0 (Ω) <109). This bias method enables the measurement of the same sample in environments with different impedance. As the impedance of the environment is increased, the current-voltage characteristics (IVCs) of the single Josephson junction and of the CPT show a well defined Coulomb blockade feature with a region of negative differential resistance, signature of the coherent tunneling of single Cooper pairs. The measured IVCs of a single Josephson junction with SQUID geometry in the high impedance environment show a qualitative agreement with the Bloch band theory as the EJ/EC ratio of the junction is tuned with the magnetic field. We also studied a single nontunable Josephson junction with strong coupling (EJ/EC > 1), where the exact dual of the overdamped Josephson effect is realized, resulting in a dual shape of the IVC, where the roles of current and voltage are exchanged. Here, we make for the first time a detailed quantitative comparison with a theory which includes the effect of fluctuations due to the finite temperature of the environment. The measurements on CPTs in the high impedance environment showed that the Coulomb blockade voltage is modulated periodically by the gate-induced charge. The gate-voltage dependence of the CPT changes from e-periodic to 2e-periodic as the impedance of the environment is increased. The high impedance environment reduces quasiparticle tunneling rates, thereby restoring the even parity of the CPT island. This behavior suggests that high impedance leads can be used to effectively suppress quasiparticle poisoning.

•Jan 1, 2006•5 citations

Superconducting quantum circuits in a tunable electromagnetic environment

S. Corlevi

This thesis presents the results of an experimental study onsmall-capacitance Josephson junctions in a high impedanceenvironment. In small-capacitance Josephson junctions the charging energyEC=e2/2C becomes relevant at low temperature and thecharging effects influence the transport properties. In theobservation of single-charge effects, a fundamental role isplayed by the impedance Z(ω) of the electromagneticenvironment surrounding the junction. To detect the tunnelingof single Cooper pairs in one junction, it is essential toembed the junction in a high impedance environment at all thefrequencies, such that Z(ω)>>RQ, where RQ=h/(2e)2= 6.45 kΩ is the quantum resistance forCooper pairs. This requirement is necessary in order to avoidthe fast discharge of the junction capacitance through theexternal circuit. In this work the effect of the high impedance environment isstudied on Cooper pair transistors (CPT) and single junctionswith tunable coupling (SQUID). The high impedance environmentis obtained by biasing the sample under test with four SQUIDarrays. The SQUID geometry, besides the modulation of thejunctions Josephson energy (EJ), allows the tuning in situ of the effective impedanceof the environment. By applying a magnetic field perpendicularto the SQUIDs loop, the zero bias resistance of the leads (R0) can be varied over several orders of magnitude(104<R0 (Ω)<108), providing the possibility to study the samesample in different electromagnetic environments. Measurements of the current-voltage (I-V) characteristic ofa single junction with SQUID geometry allow the investigationof the influence of both the electrodynamic environment and theEJ/ECratio in the same sample. As the impedance of thebiasing leads is increased (R0>>RQ), the I-V curve of the junction exhibits a welldefined Coulomb blockade feature with a region of negativedifferential resistance, evidence of the coherent tunneling ofsingle Cooper pairs. Measurements on CPT samples also show how the Coulombblockade feature in the I-V curve becomes sharper as theimpedance of the environment is increased. Furthermore theyindicate how the Coulomb blockade threshold voltage is modifiedwith the DC signal applied to the gate. When the SQUID arraysare highly resistive, the gate-induced modulation of the I-Vcurve changes frome-periodic to 2e-periodic, suggesting that high impedance leadseffectively reduce non-equilibrium quasiparticle poisoning.

•Jan 1, 2004•1 citation

Tunneling of Cooper pairs across voltage-biased asymmetric single-Cooper-pair transistors

Juha Leppäkangas, E. V. Thuneberg, Rene K. Lindell +1 more

We analyze tunneling of Cooper pairs across voltage biased asymmetric single-Cooper-pair transistors. Also tunneling of Cooper pairs across two capacitively coupled Cooper-pair boxes is considered, when the capacitive coupling and Cooper pair tunneling are provided by a small Josephson junction between the islands. The theoretical analysis is done at subgap voltages, where the current-voltage characteristics depend strongly on the macroscopic eigenstates of the island(s) and their coupling to the dissipative environment. As the environment we use an impedance which satisfies $\mathrm{Re}[Z(\ensuremath{\omega})]⪡{R}_{Q}$ and a few $LC$ oscillators in series with $Z(\ensuremath{\omega})$. The numerically calculated $I\text{\ensuremath{-}}V$ curves are compared with experiments where the quantum states of mesoscopic SQUIDs are probed with inelastic Cooper pair tunneling. The main features of the observed $I\text{\ensuremath{-}}V$ data are reproduced. Especially, we find traces of band structure in the higher excited states of the Cooper-pair boxes as well as traces of multiphoton processes between two Cooper-pair boxes in the regime of large Josephson coupling ${E}_{J}⪢{E}_{C}$.

arXiv:cond-mat/0604092•Physical Review B•Aug 7, 2006•13 citations
We have measured the current-voltage (I\ensuremath−V)(I\ensuremath{-}V)(I\ensuremath−V) characteristics of small-capacitance single Josephson junctions at low temperatures (T=0.02−−0.6K),(T=0.02--0.6\mathrm{K}),(T=0.02−−0.6K), where the strength of the coupling between the single junction and the electromagnetic environment was controlled with one-dimensional arrays of dc superconducting quantum interence devices (SQUIDs). The single-junction I\ensuremath−VI\ensuremath{-}VI\ensuremath−V curve is sensitive to the impedance of the environment, which can be tuned in situ. We have observed Coulomb blockade of Cooper-pair tunneling and even a region of negative differential resistance, where the zero-bias resistance R0\ensuremath′{R}_{0}^{\ensuremath{'}}R0\ensuremath′​ of the SQUID arrays is much higher than the quantum resistance RK\ensuremath≡h/e2\ensuremath≈26k\ensuremathΩ.{R}_{K}\ensuremath{\equiv}{h/e}^{2}\ensuremath{\approx}26\mathrm{k}\ensuremath{\Omega}.RK​\ensuremath≡h/e2\ensuremath≈26k\ensuremathΩ. The negative differential resistance is evidence of the coherent single-Cooper-pair tunneling within the theory of current-biased single Josephson junctions. Based on this theory, we have calculated the I\ensuremath−VI\ensuremath{-}VI\ensuremath−V curves numerically in order to compare then with the experimental ones at R0\ensuremath′\ensuremath≫RK.{R}_{0}^{\ensuremath{'}}\ensuremath{\gg}{R}_{K}.R0\ensuremath′​\ensuremath≫RK​. The numerical calculation agrees with the experiments qualitatively. We also discuss the R0\ensuremath′{R}_{0}^{\ensuremath{'}}R0\ensuremath′​ dependence of the single-Josephson-junction I\ensuremath−VI\ensuremath{-}VI\ensuremath−V curve in terms of the superconductor-insulator transition driven by changing the coupling to the environment.
We have measured the current-voltage characteristics of small-capacitance single Josephson junctions at low temperatures ( T< or =0.04 K), where the strength of the coupling between the single junction and the electromagnetic environment was controlled with one-dimensional arrays of dc SQUIDs. We have clearly observed Coulomb blockade of Cooper-pair tunneling and even a region of negative differential resistance, when the zero-bias resistance of the SQUID arrays is much higher than the quantum resistance h/e(2) approximately 26 kOmega. The negative differential resistance is evidence of coherent single-Cooper-pair tunneling in the single Josephson junction.
We have measured the current–voltage characteristics of small-capacitance single Josephson junctions at low temperatures T ≤ 0.04 K, where the strength of the coupling between the single junction and the electromagnetic environment was controlled with one-dimensional arrays of dc SQUIDs. When the zero-bias resistance of the SQUID arrays is much higher than the quantum resistance h/e 2 ≈ 26 kΩ, a transition to a clear Coulomb blockade of Cooper-pair tunnelling is induced in the single junction. The measured blockade voltage agrees with the theoretical prediction.
We review experiments on small-capacitance Josephson junctions. When the Josephson junction is fabricated in the configuration of dc superconducting quantum interference device (SQUID), the Josephson coupling can be tuned IN SITU with an external magnetic field. The electrical transport properties of one-dimensional arrays of small-capacitance dc SQUIDs have been investigated in order to study the superconductor-insulator transition. The arrays have also been used to bias a single Josephson junction, and a clear Coulomb blockade of Cooper-pair tunneling has been observed in the single junction.
This thesis presents the results of an experimental study on single-charge effects in nanoscale Josephson junctions and Cooper pair transistors (CPTs). In nanoscale Josephson junctions the charging energy EC becomes significant at sub-Kelvin temperatures and single-charge effects, such as the Coulomb blockade of Cooper pair tunneling, influence the transport properties. In order to observe charging effects in a single Josephson junction, the impedance of the electromagnetic environment surrounding the junction has to be larger than the quantum resistance (RQ=h/4e2≈6.45kΩ). In this work the high impedance environment is obtained by biasing the sample under test (single Josephson junction or CPT) with four one-dimensional Josephson junction arrays having SQUID geometry. The advantage of this configuration is the possibility of tuning in situ the effective impedance of the electromagnetic environment. By applying a magnetic field perpendicular to the SQUID loops, the Josephson energy EJ of the SQUIDs is suppressed, resulting in an increase of the measured zero bias resistance of the arrays of several orders of magnitude (104< R0 (Ω) <109). This bias method enables the measurement of the same sample in environments with different impedance. As the impedance of the environment is increased, the current-voltage characteristics (IVCs) of the single Josephson junction and of the CPT show a well defined Coulomb blockade feature with a region of negative differential resistance, signature of the coherent tunneling of single Cooper pairs. The measured IVCs of a single Josephson junction with SQUID geometry in the high impedance environment show a qualitative agreement with the Bloch band theory as the EJ/EC ratio of the junction is tuned with the magnetic field. We also studied a single nontunable Josephson junction with strong coupling (EJ/EC > 1), where the exact dual of the overdamped Josephson effect is realized, resulting in a dual shape of the IVC, where the roles of current and voltage are exchanged. Here, we make for the first time a detailed quantitative comparison with a theory which includes the effect of fluctuations due to the finite temperature of the environment. The measurements on CPTs in the high impedance environment showed that the Coulomb blockade voltage is modulated periodically by the gate-induced charge. The gate-voltage dependence of the CPT changes from e-periodic to 2e-periodic as the impedance of the environment is increased. The high impedance environment reduces quasiparticle tunneling rates, thereby restoring the even parity of the CPT island. This behavior suggests that high impedance leads can be used to effectively suppress quasiparticle poisoning.
This thesis presents the results of an experimental study onsmall-capacitance Josephson junctions in a high impedanceenvironment. In small-capacitance Josephson junctions the charging energyEC=e2/2C becomes relevant at low temperature and thecharging effects influence the transport properties. In theobservation of single-charge effects, a fundamental role isplayed by the impedance Z(ω) of the electromagneticenvironment surrounding the junction. To detect the tunnelingof single Cooper pairs in one junction, it is essential toembed the junction in a high impedance environment at all thefrequencies, such that Z(ω)>>RQ, where RQ=h/(2e)2= 6.45 kΩ is the quantum resistance forCooper pairs. This requirement is necessary in order to avoidthe fast discharge of the junction capacitance through theexternal circuit. In this work the effect of the high impedance environment isstudied on Cooper pair transistors (CPT) and single junctionswith tunable coupling (SQUID). The high impedance environmentis obtained by biasing the sample under test with four SQUIDarrays. The SQUID geometry, besides the modulation of thejunctions Josephson energy (EJ), allows the tuning in situ of the effective impedanceof the environment. By applying a magnetic field perpendicularto the SQUIDs loop, the zero bias resistance of the leads (R0) can be varied over several orders of magnitude(104<R0 (Ω)<108), providing the possibility to study the samesample in different electromagnetic environments. Measurements of the current-voltage (I-V) characteristic ofa single junction with SQUID geometry allow the investigationof the influence of both the electrodynamic environment and theEJ/ECratio in the same sample. As the impedance of thebiasing leads is increased (R0>>RQ), the I-V curve of the junction exhibits a welldefined Coulomb blockade feature with a region of negativedifferential resistance, evidence of the coherent tunneling ofsingle Cooper pairs. Measurements on CPT samples also show how the Coulombblockade feature in the I-V curve becomes sharper as theimpedance of the environment is increased. Furthermore theyindicate how the Coulomb blockade threshold voltage is modifiedwith the DC signal applied to the gate. When the SQUID arraysare highly resistive, the gate-induced modulation of the I-Vcurve changes frome-periodic to 2e-periodic, suggesting that high impedance leadseffectively reduce non-equilibrium quasiparticle poisoning.
We analyze tunneling of Cooper pairs across voltage biased asymmetric single-Cooper-pair transistors. Also tunneling of Cooper pairs across two capacitively coupled Cooper-pair boxes is considered, when the capacitive coupling and Cooper pair tunneling are provided by a small Josephson junction between the islands. The theoretical analysis is done at subgap voltages, where the current-voltage characteristics depend strongly on the macroscopic eigenstates of the island(s) and their coupling to the dissipative environment. As the environment we use an impedance which satisfies $\mathrm{Re}[Z(\ensuremath{\omega})]⪡{R}_{Q}$ and a few LCLCLC oscillators in series with $Z(\ensuremath{\omega})$. The numerically calculated $I\text{\ensuremath{-}}V$ curves are compared with experiments where the quantum states of mesoscopic SQUIDs are probed with inelastic Cooper pair tunneling. The main features of the observed $I\text{\ensuremath{-}}V$ data are reproduced. Especially, we find traces of band structure in the higher excited states of the Cooper-pair boxes as well as traces of multiphoton processes between two Cooper-pair boxes in the regime of large Josephson coupling EJ⪢EC{E}_{J}⪢{E}_{C}EJ​⪢EC​.