Assistant Professor
Center for Nanophysics and Advanced Materials
Department of Physics
University of Maryland
Synthesis and Exploration of SCES Materials: The common appearance of superconductivity near a quantum critical point is an excellent example of the way in which nature self-organizes to avoid its own instabilities. The 2008 discovery of high superconducting transition temperatures (Tc) in a series of metallic compounds with corrugated iron-arsenic layers has resulted in an explosion of excitement and numerous publications on what is now recognized as a new family of high-Tc superconductors. This class of compounds includes several different crystallographic structures – including RFeAsO (R = rare earth), RFe2As2 (R = rare earth), and LiFeAs – with the common element of iron-arsenic (FeAs) layers that appear to provide the key ingredient for Tc values approaching 60 K. Extremely large critical current and critical magnetic field values throughout this family of superconductors point toward strong potential use in a wide range of energy and technological applications. Most interestingly, the development of a superconducting phase in these materials appears to be intimately coupled with the suppression of magnetism [3] via chemical doping or applied pressure, providing phase diagrams strikingly similar to the numerous examples of heavy-fermion materials that exhibit identical phenomena [4]. However, the temperature scales associated with the iron-based superconductors are orders of magnitude larger than f-electron systems, making this the second transition metal-based system to harbor a completely unexpected superconducting instability; this warrants our utmost attention.
Anisotropy in Quantum Materials: This group performs condensed matter experiments at ultra-low temperatures and high magnetic fields to study materials which defy the current textbook understanding of metals, magnets and insulators. Our main focus is the measurement of transport and thermodynamic properties of strongly correlated electron systems tuned toward a phase transition at absolute zero temperature via applied pressure, magnetic field or chemical substitution. This involves:
- testing the quasi-particle picture in the limit of strong electronic correlations
- investigating non-Fermi liquid behavior in heavy-electron systems
- probing the nature of unconventional superconductivity
- searching for new physical phenomena at experimentally tunable extremes.
To elucidate the role of anisotropy in such phenomena, we are setting up a unique experimental facility which will allow systems to be studied using a number of techniques in conjunction with the precise 360 degree rotational capability of a high-field vector magnet. Because these phenomena often involve extremely low energy scales, experiments are required to be performed down to the millikelvin temperature range, thousandths of a degree above absolute zero.