Spontaneous spin polarization and charge localization in metal nanowires: the role of ageometric constriction

Abstract

An idealized jellium model of conducting nanowires with a geometric constriction is investigatedby density functional theory (DFT) in the local spin density (LSD) approximation. The resultsreveal a fascinating variety of spin and charge patterns arising in wires of sufficiently low (rs ≥ 15) average electron density, pinned at the indentation by an apparent attractive interactionwith the constriction. The spin-resolved frequency-dependent conductivity shows a markedasymmetry in the two spin channels, reflecting the spontaneous spin polarizationaround the wire neck. The relevance of the computational results is discussed inrelation to the so-called 0.7 anomaly found by experiments in the low-frequencyconductivity of nanowires at near-breaking conditions (see 2008 J. Phys.: CondensMatter 20, special issue on the 0.7 anomaly). Although our mean-field approachcannot account for the intrinsic many-body effects underlying the 0.7 anomaly, itstill provides a diagnostic tool to predict impending transitions in the electronicstructure.