RELAXATION OF THE COOPER PAIR DENSITY.

In a Fermi gas with a Fashbach resonance, one can tune the strengthof the paring interaction by adjusting the threshold energy of Feshbachresonance. The super-fluid density s is always equal to the total carrierdensity  at T  0 which it vanishes at the super-fluid phase transition c T .These properties are satisfied in both Fermi and Bose super-fluid. There is acrucial difference between s in a Fermi superfluid and that in a Bose superfluid.In a mean field BCS theory originates from the thermal dissociationof cooper pairs.There it was observed that that if one increases the strength of thepairing interaction BCS type normal fluid density dominated by quasi-particleexcitation change into BES type normal fluid density dominated byBogoliubov collective excitations. As super-fluid density s plays animportant role in two fluid hydrodynamics these evaluated results would beuseful in the study of dynamical properties in the BCS-BEC crossover regionat finite temperature.In a Fermi gas with a Fashbach resonance, one can tune the strengthof the paring interaction by adjusting the threshold energy of Feshbachresonance. The super-fluid density s is always equal to the total carrierdensity  at T  0 which it vanishes at the super-fluid phase transition c T .These properties are satisfied in both Fermi and Bose super-fluid. There is acrucial difference between s in a Fermi superfluid and that in a Bose superfluid.In a mean field BCS theory originates from the thermal dissociationof cooper pairs.There it was observed that that if one increases the strength of thepairing interaction BCS type normal fluid density dominated by quasi-particleexcitation change into BES type normal fluid density dominated byBogoliubov collective excitations. As super-fluid density s plays animportant role in two fluid hydrodynamics these evaluated results would beuseful in the study of dynamical properties in the BCS-BEC crossover regionat finite temperature.

THE SCIENTIFIC TEMPERJul 25, 20190 citations

Density dependence of the energy of N Cooper pairs

Monique Combescot, Tristan Cren, Michel Crouzeix +1 more

The European Physical Journal BMar 1, 20119 citations

Dissecting Cooper Pairs

ScienceMay 31, 20120 citations

Single Cooper-pair pumping in the adiabatic limit and beyond

Simone Gasparinetti, Paolo Solinas, Y. Yoon +1 more

We demonstrate controlled pumping of Cooper pairs down to the level of a single pair per cycle, using an rf-driven Cooper-pair sluice. We also investigate the breakdown of the adiabatic dynamics in two different ways. By transferring many Cooper pairs at a time, we observe a crossover between pure Cooper-pair and mixed Cooper-pair-quasiparticle transport. By tuning the Josephson coupling that governs Cooper-pair tunneling, we characterize Landau-Zener transitions in our device. Our data are quantitatively accounted for by a simple model including decoherence effects.We demonstrate controlled pumping of Cooper pairs down to the level of a single pair per cycle, using an rf-driven Cooper-pair sluice. We also investigate the breakdown of the adiabatic dynamics in two different ways. By transferring many Cooper pairs at a time, we observe a crossover between pure Cooper-pair and mixed Cooper-pair-quasiparticle transport. By tuning the Josephson coupling that governs Cooper-pair tunneling, we characterize Landau-Zener transitions in our device. Our data are quantitatively accounted for by a simple model including decoherence effects.

arXiv:1206.0193Physical Review BAug 2, 201218 citations

Probing Cooper Pairs with Pair Transfer

G. Potel, Ricardo A. Broglia

Cambridge University Press eBooksOct 21, 20210 citations

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 ${E}_{J}⪢{E}_{C}$ .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/0604092Physical Review BAug 7, 200613 citations

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}