Superconductivity has been one of the profound quantum phases in condensed matter physics. Efforts to identify and develop room temperature superconducting materials are an intensive area of research, motivated by both fundamental science and the prospects for applications. More than a century of rigorous research has led physicists to believe that the highest Tc that can be achieved is 40K for conventional superconductors. However, the recent discovery of superconductivity in hydrogen sulfide at 203K1 changed the notion of what might be possible for phonon–mediated superconductors. In this talk, I will discuss recent developments on high pressure room temperature superconductivity.An important discovery leading to room-temperature superconductivity is the pressure-driven disproportionation of hydrogen sulfide (H2S) to H3S, with a confirmed transition temperature of 203 kelvin at 155 gigapascals1. Both H2S and CH4 readily mix with hydrogen to form guest–host structures at lower pressures, and are of comparable size at 4 gigapascals. By introducing methane at low pressures into the H2S + H2 precursor mixture for H3S, molecular exchange is allowed within a large assemblage of van der Waals solids that are hydrogen-rich with H2 inclusions; these guest–host structures become the building blocks of superconducting compounds at extreme conditions. I shall present our most recent results on superconductivity in a photochemically transformed carbonaceous sulfur hydride system, starting from elemental precursors, with a maximum superconducting transition temperature of 287.7 kelvin (about 15 degrees Celsius) achieved at 267 ± 10 gigapascals2. Superconductivity is established by the observation of zero resistance, a magnetic susceptibility, and reduction of the transition temperature under an external magnetic field of up to 9 tesla, with an upper critical magnetic field of about 62 tesla according to the Ginzburg–Landau model at zero temperature. The Raman spectroscopy is used to probe the chemical and structural transformations before metallization. The discovery achieves the more than a century long quest to find room temperature superconductivity, a phenomenon that was first observed by Kamerlingh Onnes in 19113-5. Finally, I shall discuss future research directions in probing room temperature superconductivity by introduction of chemical tuning within our ternary system at ambient pressures.1.

Drozdov, A. P., Eremets, M. I., Troyan, I. A., Ksenofontov, V. & Shylin, S. I. Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system. Nature 525, 73–76 (2015)2.

Elliot Snider, Nathan Dasenbrock-Gammon, Raymond McBride, Mathew Debessai, Hiranya Vindana, Kevin Vencatasamy, Keith Lawler, Ashkan Salamat, Ranga P. Dias “Room Temperature Superconductivity in a Carbonaceous Sulfur Hydride” Nature 586, 373-377 (2020)3.

Elliot Snider, Nathan Dasenbrock-Gammon, Raymond McBride, Noah Meyers, Keith Lawler, Ashkan Salamat, Ranga P. Dias “Superconductivity to 262 kelvin via catalyzed hydrogenation of yttrium at high pressures” Phys. Rev. Lett. 126, 117003 (2021)4.

Suxing X. Hu, Reetam Paul, Valentin V. Karasiev, Ranga P. Dias, “Carbon-Doped Sulfur Hydrides as Room-Temperature Superconductors at 270 GPa" Under review (2021)5.

Xiaoyu Wang, Tiange Bi, Katerina P. Hilleke, Anmol Lamichhane, Russell J. Hemley, and Eva Zurek, “A Little Bit of Carbon Can do a Lot for Superconductivity in H3S” Under review (2021)