Superconductivity and Magnetism: Friends after all?
* SPEAKERS
Name
Affiliation
E-mail
InJae Lee
Chonbuk National University
* HOST(Applicant)
Name
Affiliation
E-mail
-
* DATE / TIME
2005-09-09, 2:30p.m.
* PLACE
APCTP Seoul Branch Office (과총회관 신관 11층 3호)
* ABSTRACT
Since the discovery of superconductivity in charge transfer salts based on tetramethyltetraslenafulvalene molecule in the early 1980’s, the quasi-one-dimensional metals or so called Bechgaard salts (TMTSF)2X (where X=PF6, ClO4, ReO4, NO3, etc.) have attracted a lot of attention for their exotic physical properties, such as spin density waves (SDW), quantum Hall effects associated with a field induced SDW, quantum oscillations, angular dependent ground states related to magic angle effects and a possible unconventional superconductivity. Recently, a new light has been shed on the issue of order parameter symmetry by measurements of the resistive upper critical field Hc2 that vastly exceeds the Clogston-Chandrasekhar or Pauli pair-breaking limit. Here I present detailed resistive upper critical field studies and a pulsed NMR Knight shift (K) study of 77Se in pressurized (TMTSF)2PF6, which strongly support triplet spin pairing.
In addition to being a spin triplet superconductor, the nature of the strong suppression of orbital diamagnetic frustration is of great interest, since it may point a way toward high critical field materials. Previously the high critical field has been attributed to a field-induced dimensional crossover/decoupling. From number of experiments that designed to critically test this hypothesis, surprisingly, we find that the upper critical field is greatly enhanced by the proximity of spin density wave phase. The value and upward curvature of the critical field are increased as the pressure is lowered toward the SDW-superconducting critical pressure. An alternative model for the strong suppression of the orbital superconducting frustration, similar to macroscopic structure in the intermediate superconducting state, will be discussed.
