Magnetic Frustration in a Prototypical Strongly Correlated Electron System
A unifying theme among various types of quantum matter is the ubiquity of energetically neardegenerate ground states. For example, in strongly-correlated electron systems unconventional superconductivity typically emerges in the vicinity of a magnetic quantum phase transition and competes with electronic-nematic, charge density, and magnetic phases. Alternatively, frustrated magnetic short-range interactions are prone to generate a multitude of degenerate magnetic configurations leading to quantum spin liquid physics. This suggests that the rich landscape of quantum ground states in certain materials may be concurrently controlled by both mechanisms. Here we demonstrate via high-resolution neutron spectroscopy in applied magnetic fields that prototypical strongly-correlated electron material CeRhIn5, in which superconductivity emerges near a magnetic quantum phase transition, also exhibits magnetic frustration. Notably, the complex temperature vs. magnetic field phase diagram is reproduced by the Axial-Next-Nearest-Neighbor (ANNNI) model¾an archetypal framework for describing frustrated magnetic interactions. The observation of magnetic frustration not only identifies CeRhIn5 as the first heavy fermion material that exhibits ANNNI physics but also suggests that a complete model of magnetic quantum criticality and the associated emergent phases needs to consider magnetic frustration [1, 2].
 P. Das, S.-Z. Lin, N. J. Ghimire, K. Huang, F. Ronning, E. D. Bauer, J. D. Thompson, C. D. Batista, G. Ehlers, M. Janoschek, Phys. Rev. Lett. 113, 246403 (2014).
 D. M. Fobes, S.-Z. Lin, Pinaki Das, N. J. Ghimire, E. D. Bauer, J. D. Thompson, L. Harringer, G. Ehlers, A. Podlesnyak, R. Bewley, F. Ronning, C. D. Batista, and M. Janoschek, in preparation.
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