Muonium hydride: The lowest density crystal

A muonium hydride molecule is a bound state of and hydrogen atoms. It has half the mass parahydrogen very similar electronic properties in its ground state. The phase diagram an assembly such particles investigated by first-principles quantum simulations. In bulk limit, low-temperature equilibrium crystal extraordinarily low density, lower than that any other known atomic or molecular crystal. Despite density particle mass, melting temperature surprisingly high (close to 9 K). No (metastable) supersolid observed. We physical nanoscale clusters (up 200 particles) found superfluid response be greatly enhanced compared clusters. possible experimental realization these systems discussed.Received 13 March 2021Accepted 23 April 2021DOI:https://doi.org/10.1103/PhysRevResearch.3.023113Published American Physical Society under terms Creative Commons Attribution 4.0 International license. Further distribution this work must maintain attribution author(s) published article's title, journal citation, DOI.Published SocietyPhysics Subject Headings (PhySH)Research AreasEquations statePhysical SystemsMuonic atoms & moleculesTechniquesPath-integral Monte CarloCondensed Matter, Materials Applied Physics