Events

Department of Magnetic Reseach Seminar

Structural complexity of CeIrIn5 and CeCoIn5: From macroscopic to atomic length scales

prof. Steffen Wirth

Instytut Maxa Plancka Fizyki Chemicznej w Dreźnie w Niemczech

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Streszczenie:

The hybridization between 4f and conduction electrons in heavy fermion metals often results in the generation of low-energy scales that can induce quantum criticality and unconventional superconductivity[1]. In this context, the CeMIn5 family of compounds offers an interesting playground as an intricate interplay of superconductivity (SC) and magnetism has been observed [2,3]. This is particularly obviousfor the Cd-substituted CeCoIn5 for which a co-existence of antiferromagnetism and SC was found [4].

The investigation of such complex physical properties requires detailed knowledge of the structural properties of the materials. We here combine chemical investigations by enhanced resolution single-crystal X-ray diffraction (XRD) experiments with atomically resolved Scanning Tunnelling Microscopy (STM) on CeIrIn5 and CeCoIn5 [5]. From the difference electron density calculated from XRD experiments on CeIrIn5, we infer, in addition to the majority structural patterns of the HoCoGa5-type structure, also the existence of a very small amount of about 1.2% of the closely related TlAsPd5-type atomic arrangement. Similar results were obtained for CeCoIn5.

The coexistence of the two atomic arrangements in our single crystalline samples has directly been visualized by atomically resolved STM. This, however, requires cleavage of the samples along a crystallographic plane different from the (001) plane, which is well in agreement with the analysis of chemical bonding in the CeIrIn5 and CeCoIn5 compounds. More generally we believe that, whenever such closely related structural motifs exist for a given material, they may present a genuine, yet difficult to detect source of material imperfections.

[1] S. Wirth and F. Steglich, Nature Rev. Mat. 1 (2016) 16051.

[2] J.D. Thompson and Z. Fisk, J. Phys. Soc. Jpn. 81 (2012) 011002.

[3] T.Willers et al., Proc. Natl. Acad. Sci. USA 112 (2015) 2384.

[4] Sunil Nair et al., Proc. Natl. Acad. Sci. USA 107 (2010) 9537.

[5] S. Wirth et al., J. Phys. Soc. Jpn. 83 (2014) 061009.