Abstract
The low-temperature thermal expansion of single crystals measured parallel and perpendicular to magnetic fields oriented along the axis yields the volume thermal-expansion coefficient . Considerable deviations of from Fermi-liquid behavior occur already within the superconducting region of the (, ) phase diagram and become maximal at the upper critical field . However, and the Grüneisen parameter are incompatible with a quantum critical point at , but allow for a quantum criticality shielded by superconductivity and extending to negative pressures for . We construct a tentative (, , ) phase diagram of suggesting a quantum critical line in the (, ) plane.
- Received 15 October 2010
DOI:https://doi.org/10.1103/PhysRevLett.106.087003
© 2011 American Physical Society