Welcome
Our group's research focuses on novel electron interactions in materials, including those exhibiting superconductivity, magnetism, and heavy fermion behavior, as well as quantum phase transitions, non-Fermi liquid behavior, and nontrivial topological states. Basically, we investigate the weird ways in which electrons organize themselves in complicated materials. This site will introduce you to our research projects and our people.
Are you interested in researching new Quantum Materials? Apply for an NRC Postdoc
(US Citizens) Motivated researchers looking to work at the forefront of materials synthesis, electronic property characterization, and spectroscopy are invited to apply for a prestigious NRC postdocdoral fellowship. The postdoctoral positions are research-only positions that allow the successful candidate to pursue a self-driven research program making use of research facilities and opportunities to collaborate at both NIST and UMD. Please contact me if you are interested to discuss the application process. There are two competitions per year, with due dates in February and August.
Recent Highlights
A Halo for Lazarus
We extend measurements of e unique superconducting Lazarus state outside of the b-c plane and reveal its core structure. The superconductivity wraps around the b axis in a halo-like fashion. In other words, this superconducting state, which exists in fields above 73 teslas, is stabilized by a field component perpendicular to the magnetic easy axis. These remarkable field scales further underscore UTe2's unique magnetophilic superconducting tendencies and suggest an underlying pairing mechanism that is qualitatively distinct from known theories for field-enhanced superconductivity.
S. K. Lewin, P. Czajka, et al. arXiv:2402.18564
Orphaned Superconductivity Published
We show that in UTe2 crystals extreme applied magnetic fields give rise to an unprecedented high-field superconductor that lacks a zero-field antecedent.The stability of field-induced orphan superconductivity presented in this work defies both empirical precedent and theoretical explanation and demonstrates that high-field superconductivity can exist in an otherwise non-superconducting material.
Frank, C.E., Lewin, S.K., Saucedo Salas, G. et al. Orphan high field superconductivity in non-superconducting uranium ditelluride. Nat Commun 15, 3378 (2024).
Density Wave Demesne
A pair of papers describing scanning tunneling microscopy studies of density waves in UTe2 were recently published in Nature. The results, from collaborations with the Madhavan (Aishwarya, A. et al. Nature 618, 928–933 (2023)) and Davis (Gu, Q. et al. Nature 618, 921–927 (2023)) research groups, suggest that density wave instabilities are closely tied to the unusual superconductivity observed in UTe2.
Further reading: EurekAlert, Phys.org, AZoQuantum, yahoo!finance.
Congratulations Corey
The NIST chapter of Sigma Xi held the 30th Early-Career Poster Presentation in May 2023. Corey (a chemist by training) won most outstanding poster in the physics category for her poster “Understanding unconventional superconductivity in very high magnetic fields.”
Frank, C.E., Lewin, S.K., Saucedo Salas, G. et al. Orphan high field superconductivity in non-superconducting uranium ditelluride. Nat Commun 15, 3378 (2024).
Orphaned Lazarus
We discovered that the high-field reentrant "Lazarus" superconducting phase of UTe2 survives in crystals in which disorder has quashed the zero-field superconducting phase. This is completely unexpected, because typically, superconductivity is destabilized by magnetic fields and should therefore be more sensitive to disorder. We detected superconductivity between 37 T and 52 T, which are still very high magnetic fields. This very unusual behavior deepens the mystery of high-field reentrant superconductivity - what underlying mechanism makes this possible?
C. E. Frank et al, arXiv:2304.12392 .
Kondo lattice correlations
The temperature dependence of the low-energy magnetic excitations in the spin-triplet superconductor UTe2 was measured via inelastic neutron scattering in the normal and superconducting states. These excitations have a peak instensity at 4 meV, follow the Brillouin zone edges near the crystallographic b-axis, obey the paramagnetic structural symmetry, and track the temperature evolution of the heavy fermion bulk magnetic susceptibility. Thus, the imaginary part of the dynamic susceptibility follows the behavior of interband correlations in a hybridized Kondo lattice with an appropriate characteristic energy.
N. P. Butch et al, npj Quantum Materials 7, 39 (2022).
Congratulations Sylvia
The NIST chapter of Sigma Xi held the 29TH Annual SIGMA XI Early-Career Poster Presentation in March 2022. Sylvia was one of two winners in the physics category for her poster “Anisotropy of the Superconducting Upper Critical Field in UTe2.”
Looking for Older Highlights? (Archived)