Events

Interdisciplinary Seminar of International Laboratory of High Magnetic Fields and Low Temperatures PAS

Opportunities and challenges in high-pressure synthesis of complex oxides and intermetallic superconductors

dr Nikolai D. Zhigadlo

Laboratory for Solid State Physics, ETH Zurich, Switzerland

In this talk I will provide some new insights into the materials synthesis and the crystal growth of modern superconductors, where high-pressure conditions are often crucial for the success. After a short introduction to the technological aspects and the role of high-pressure, high-temperature techniques in inorganic synthesis, I will focus on some typical examples encompassing our most recent achievements.

First, I will review the high-pressure exploration of the Mg-B-N system. Here we discovered the simultaneous crystal growth of completely different types of materials: a rare two-band superconductor MgB₂ and a wide-band semiconductor hBN. Besides the interesting physics, both these materials hold great potential for practical applications.

Successively, I will highlight the key role of the extreme conditions in the growth of Fe-based superconductors, where a careful control of the composition-structural relations is vital for understanding the material behavior. The availability of high-quality Ln1111 single crystals allowed us to obtain intrinsic and directionally dependent superconducting properties, such as H_c2, J_c, and their anisotropies. In addition, in SmFeAs(O,F) we could observe also a distinct change in the nature of the vortices: from well-pinned slow-moving Abrikosov-like to weakly-pinned fast-flowing Josephson-like. The varying nature of the vortices reflects a delicate balance between some key material properties, such as the coherence length and the interlayer separation.

Finally, I will further emphasize the beneficial role of the high-pressure, high-temperature conditions in exploring the crystal growth of various intermetallic superconductors, such as MgCNi₃, Mo₃Al₂C, and APt₃P (A = Sr, Ca, La). The underlying correlations and the general trends between composition, structure, and superconductivity in these superconducting materials will be discussed as well.