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HL: Fachverband Halbleiterphysik

HL 16: Frontiers in Electronic-Structure Theory - Focus on Electron-Phonon Interactions II (joint session O/CPP/DS/HL)

HL 16.9: Vortrag

Montag, 16. März 2020, 17:00–17:15, GER 38

Energy gap closure of crystalline molecular hydrogen with pressure — •Vitaly Gorelov¹, Markus Holzmann^2,3, David M. Ceperley⁴, and Carlo Pierleoni^5,1 — ¹Maison de la Simulation, CEA-Saclay, Gif-sur-Yvette, France — ²Univ. Grenoble Alpes, CNRS, LPMMC, Grenoble, France — ³Institut Laue-Langevin, Grenoble, France — ⁴Department of Physics, University of Illinois Urbana-Champaign, USA — ⁵Department of Physical and Chemical Sciences, University of L’Aquila, L’Aquila, Italy

We study the gap closure with pressure in Phases III and IV of molecular crystalline hydrogen. Nuclear quantum and thermal effects are considered from first principles with Coupled Electron Ion Monte Carlo. The fundamental electronic gaps are obtained from grand-canonical Quantum Monte Carlo methods properly extended to quantum crystals. Nuclear zero point effects cause a large reduction in the gap (∼ 2eV). As a consequence the fundamental gap closes at 530GPa for ideal crystals while at 360GPa for quantum crystals. Since the direct gap remains open until ∼450GPa, the emerging scenario is that upon increasing pressure in phase III (C2/c-24 crystal symmetry) the fundamental (indirect) gap closes and the system enters into a bad metal phase where the density of states at the Fermi level increases with pressure up to ∼450GPa when the direct gap closes. Our work partially supports the interpretation of recent experiments in high pressure hydrogen.