Salamon Featured In Nature Article

When water crystallizes into ice, H₂O molecules are either in a liquid state or in a solid crystalline state, or a mixture of the two-depending on temperature and pressure. Researchers at Illinois and Los Alamos National Laboratory studying the material CeRhIn5 have demonstrated that its magnetic state can coexist with another state-superconductivity in a certain range of temperature and pressure.

At absolute zero, unconventional superconductivity--formed by electron pairs dancing at the surface of an electron sea--hides a background of antiferromagnetism. Applying a magnetic field reveals magnetism coexisting with superconducting electron partners.

In a letter published in the March 2 edition of Nature, the researchers describe the discovery that the magnetism is merely hidden by unconventional superconductivity, but can be made to reappear in the presence of an applied magnetic field.

"Hidden broken symmetries and quantum-phase transitions underlie theoretical models of how Nature is organized, ranging from the fabric of the cosmos to the most fundamental components of elementary particles," said Tuson Park, the letter's principal author. "CeRhIn5 has provided a bench-top example in which the presence of a hidden broken symmetry is revealed as well as its relationship to phase transitions controlled by quantum fluctuations. These discoveries, though specific to condensed matter, underpin broadly applicable concepts common to diverse classes of quantum problems."

The letter, entitled, "Hidden Magnetism and Quantum Criticality in the Heavy Fermion Superconductor CeRhIn5" by Tuson Park, F. Ronning, H.Q. Yuan, M.B. Salamon, R. Movshovich, J.L. Sarrao, and J.D. Thompson, notes that the point at which magnetism becomes hidden actually lies on a line of quantum critical points separating a purely unconventional superconducting phase from a phase of coexisting magnetism and unconventional superconductivity. Such behavior can be explained quantitatively by a theory developed explicitly in the context of the high-Tc cuprates, but which has been impossible to test so definitively in the cuprates. These discoveries provide an entirely new framework that unifies the relationship among magnetism, unconventional superconductivity, and quantum criticality in cuprate and heavy-fermion systems.

This work is one in a series of ongoing collaborations between Salamon's group at Illinois and the Condensed Matter and Thermal Physics Group at Los Alamos. Park, the principal author of the letter, received his PhD under Salamon's guidance and is now an Oppenheimer postdoctoral fellow at Los Alamos.

"I try to send my best students to work with Dr. Thompson's group at LANL," Salamon said.

This work was supported by the National Science Foundation, ICAM, and the Office of Basic Energy Sciences in the U.S. Department of Energy Office of Science.

Illustration courtesy of Tuson Park, Los Alamos Laboratory.

Nature Article