Two protons, two positrons, and four electrons: Covalent bond with van der Waals characteristics.

Quantum Monte Carlo reveals positronium hydride dimer forms covalent-like bonds with van der Waals strength, involving delocalized positrons and collective dipole response.

• Why it matters: Understanding bonding mechanisms in matter-antimatter systems is crucial for advancing fundamental physics and could uncover new types of quantum interactions beyond traditional classifications.
• What they did: The study used accurate quantum Monte Carlo calculations to analyze a PsH dimer composed of two protons, two positrons, and four electrons, revealing delocalized positronic orbitals and collective dipole behavior.
• The result: Findings indicate that positronic bonds resemble covalent bonds but with van der Waals strength, suggesting that delocalized proto-bonds may be a general property of quantum systems involving particles, antiparticles, and quasiparticles.