ABSTRACT
Some of the highest-transition-temperature superconductors across various materials classes exhibit linear-in-temperature 'strange metal' or 'Planckian' electrical resistivities in their normal state. It is thus believed by many that this behavior holds the key to unlock the secrets of high-temperature superconductivity. However, these materials typically display complex phase diagrams governed by various competing energy scales, making an unambiguous identification of the physics at play difficult. Here we use electrical resistivity measurements into the micro-Kelvin regime to discover superconductivity condensing out of an extreme strange metal state-with linear resistivity over 3.5 orders of magnitude in temperature. We propose that the Cooper pairing is mediated by the modes associated with a recently evidenced dynamical charge localization-delocalization transition, a mechanism that may well be pertinent also in other strange metal superconductors.
ABSTRACT
The magnetic susceptibility of 3He nanoclusters embedded in a 4He matrix has been measured from 0.5 to 10 mK at pressures from 2.88 to 3.54 MPa. Even the lowest pressure clusters have a solid fraction in the region of the phase diagram where bulk solid is unstable. At 3.54 MPa, straight theta = -250 microK, equal to that of bulk 3He for v = 21.3 cm3/mole. For 2.88 MPa, straight theta = 140 microK, indicating a ferromagnetic tendency, similar to 2D films at some coverages. At intermediate pressures, chi has a peak near 1.05 mK, but with no discontinuity. Magnetic ordering in nanoclusters appears to be different than the U2D2 phase of bulk 3He.
