Philip Moll

Jeudi 14 Juin 2018 à 14h00, salle C313 « Nobelium »,
Bat C, 3eme étage

Nematicity and superconductivity in heavy fermions : a microstructure perspective.

Focused Ion Beam (FIB) micromachining of single crystals is a promising route towards new insights into quantum materials. Single crystals can be shaped into arbitrary geometries on the sub-micron scale, thus enabling experiments on traditionally synthesized crystals that previously were only possible in thin-films. In an ongoing project, we explore the behavior of the heavy fermion superconductor CeRhIn5 in high magnetic fields. At the heart of the heavy-fermion problem is the rich interaction between f-electrons and the itinerant electronic system. Their character may be best described in localized or itinerant pictures, depending on the Kondo- and RKKY-interactions. CeRhIn5 falls in the localized category, and antiferromagnetism appears at TN 3.9K. Applying pressure increases the hybridization, and thus magnetism is suppressed in favor of superconductivity. Magnetic fields are another important parameter tuning the 4f-waveform, and recently a peculiar transition at H* 28T into a new phase emerging in vicinity of field-tuned AFM quantum critical point at Hc 50T has been reported. In-plane resistivity anisotropy devices has uncovered experimental evidence for a nematic character of this high-field phase. Electronic nematics are characterized by a lowered symmetry of the electronic system compared to the underlying lattice, in analogy to the directional alignment without translational order in nematic liquid crystals. In the nematic phase, a substantial in-plane resistivity anisotropy appears in the presence of a small in-plane field component. The anisotropy has little apparent connection to the underlying lattice, rendering it a candidate for XY-nematicity. In an ongoing study, we combine three extreme experimental conditions : magnetic fields up to 65T, temperatures down to 450mK, and pressure up to 40kBar by integrating FIB machining with diamond anvil cell technology. This allows us to directly investigate the connection between nematicity, AFM order and superconductivity in the (H,p) phase diagram.

FIB structures for high pressure experiments.

References:FIB structures for high pressure experiments.
References :
[1] F. Ronning et al., Nature 548, 313–317 (2017)
[2] T. Helm et al., unpublished

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