Speaker: Tim Strobel, Carnegie Science

Host: Chandan Setty

Title: High-Pressure Pathways to New Superconductors

Abstract: High pressure provides a unique route to materials that are inaccessible through conventional synthesis. This talk will highlight recent developments in superconductors discovered under pressure, with an emphasis on strategies for reducing the pressure required for synthesis or superconductivity and, ultimately, recovering novel phases to ambient conditions.

We begin with hydrides, which host the highest known conventional superconducting transition temperatures. In the Sr–Pd–H system, we demonstrate superconductivity for the first time in the perovskite hydride structural prototype. Although T_c in SrPdH₃ is relatively low (~2 K), comparison with the deuteride provides evidence for an inverse isotope effect. Unlike the well-known inverse isotope effect in PdH, which is generally associated with strong anharmonicity, our results suggest a distinct mechanism involving nuclear quantum motion, with important implications for ongoing discovery campaigns [1]. More broadly, we propose complex transition-metal hydrides as a promising platform for higher-T_c superconductivity at reduced pressures. We demonstrate that metallic and superconducting behavior is possible in compounds such as Mg₄Pt₃H₁₂ [2], while calculations predict substantially higher T_c in structures such as Mg₂IrH₆ [3]. We will describe our efforts to access this metastable phase experimentally and the discoveries of the neighboring compositions Mg₂IrH₅ and Mg₂IrH₇ [4–5].

We then turn to borocarbides, where strong, diamond-like covalent bonding can stabilize high-pressure structural motifs after decompression. Borocarbide frameworks adopt many of the same structural architectures found in high-T_c superhydrides, while offering the possibility of recovery to ambient conditions. We will discuss the discovery of new clathrate and clathrate-like borocarbides, including several zeolite-derived frameworks that support superconductivity [6–8]. Finally, we report MgBC, a new MgB₂-like borocarbide that becomes stable above ~20 GPa and can be recovered to ambient pressure. MgBC provides an unusual example of a superconducting material that was first predicted computationally and subsequently realized experimentally, and represents a promising direction for the targeted discovery of recoverable high-pressure superconductors.

[1] W. Lu et al., https://doi.org/10.48550/arXiv.2602.23691 (2026).

[2] W. Lu et al., Phys. Rev. B. 112, 094513 (2025).

[3] K. Dolui et al., Phys. Rev. Lett. 132, 166001 (2024).

[4] M.F. Hansen et al., Phys. Rev. B., 110 214513 (2024).

[5] S. Sinha et al., https://arxiv.org/abs/2602.23675 (2026).

[6] L. Zhu et al., Phys Rev. Res., 5, 01312 (2023).

[7] T.A. Strobel et al., Sci. Advances, 11, eadv6867 (2025). 

[8] T.A. Strobel et al., J. Am. Chem. Soc., 148, 35233 (2026).

Bio:Timothy Strobel is a Staff Scientist at Carnegie Science’s Earth and Planets Laboratory. He received his B.S. and Ph.D. in Chemical Engineering from the Colorado School of Mines, where his doctoral research focused on hydrogen storage in clathrate materials. He joined Carnegie as a Postdoctoral Fellow in 2008 and became a Staff Scientist in 2011.

Strobel’s research focuses on the discovery and synthesis of new materials using high-pressure and high-temperature conditions, with particular emphasis on metastable materials, superconductors, and carbon- and boron-rich framework structures. His group combines advanced synthesis and characterization techniques with first-principles computation to address a central challenge in materials discovery: not simply predicting materials with desirable properties, but determining whether and how they can actually be made. Current efforts include developing synthesis pathways to access metastable structures, recovering high-pressure phases to ambient conditions, and discovering new superconducting hydrides and covalent framework materials.