Sodium: A Charge-Transfer Insulator at High Pressures
Abstract
By first-principles methods we analyze the optical response of transparent dense sodium as a function of applied pressure. We discover an unusual kind of charge-transfer exciton that proceeds from the interstitial distribution of valence electrons. The absorption spectrum is strongly anisotropic, which, just at pressures above the metal-insulator transition, manifests as sodium being optically transparent in one direction but reflective in the other. This result provides key information about the crystal structure of transparent sodium, a new unconventional inorganic electride.
- Publication:
-
Physical Review Letters
- Pub Date:
- May 2010
- DOI:
- 10.1103/PhysRevLett.104.216404
- arXiv:
- arXiv:1003.0540
- Bibcode:
- 2010PhRvL.104u6404G
- Keywords:
-
- 71.35.Cc;
- 61.50.Ks;
- 71.20.Dg;
- 78.40.-q;
- Intrinsic properties of excitons;
- optical absorption spectra;
- Crystallographic aspects of phase transformations;
- pressure effects;
- Alkali and alkaline earth metals;
- Absorption and reflection spectra: visible and ultraviolet;
- Condensed Matter - Materials Science
- E-Print:
- revtex4, 5+8 pages