Choice between singlet and triplet superconductivity

Tian De Cao, Tie Bang Wang

Cecilia Holmqvist

A. G. Lebed, Omjyoti Dutta

Yoshiki Hori, Akira Goto

Phase boundary between spin singlet and triplet superconductivity in the extended Hubbard model with exchange interaction on a square lattice is calculated within meanfield approximation. Basically, antiferromagnetic exchange interaction J is advantageous for the singlet pairing, while ferromagnetic J prefers the triplet pairing. When off-site interaction V is repulsive, the singlet phase and the triplet phase are separated by normal state in the phase diagram against V and J . If V is effectively attractive, however, the singlet and triplet states can compete against each other. We calculate the phase boundary between singlet and triplet phase for various band filling. It is shown that the triplet phase penetrates rather deeply into antiferromagnetic exchange regime for lower band filling, whereas the penetration of the singlet phase is confined in a narrow range of ferromagnetic exchange regime.

Mohammad Alidoust, Klaus Halterman, Jacob Linder

Motivated by the recent experimental realization of a quantum interference transistor based on the superconducting proximity effect, we here demonstrate that the inclusion of a textured ferromagnet both strongly enhances the flux sensitivity of such a device and additionally allows for singlet-triplet switching by tuning a bias voltage. This functionality makes explicit use of the induced spin-triplet correlations due to the magnetic texture. Whereas the existence of such triplet correlations is well known, our finding demonstrates how spin-triplet superconductivity may be utilized for concrete technology, namely, to improve the functionality of ultrasensitive magnetometers.

David Abergel