2002/05/23 by J. D. Jorgensen, D. G. Hinks, Jorgensen, J. D. +9 · 1 citation
Materials Science · Physics and Astronomy · #Boron and Carbon Nanomaterials Research #FOS: Physical sciences #Physics of Superconductivity and Magnetism #Superconductivity (cond-mat.supr-con) #Superconductivity in MgB2 and Alloys #cond-mat.supr-con
paper · pdf · doi:10.48550/arxiv.cond-mat/0205486
11 pages, 4 figures
arxiv created 2002/05/23 · openalex publication_date 2002/05/23 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
An anisotropic lattice anomaly near the superconducting transition temperature, Tc, was observed in MgB2 by high-resolution neutron powder diffraction. The a-axis thermal expansion becomes negative near Tc, while the c-axis thermal expansion is unaffected. This is qualitatively consistent with a depletion of the boron-boron s-band as the superconducting gap opens, resulting in weaker bonding. However, the observed anomaly is much larger than predicted by the Ehrenfest relation, strongly suggesting that the phonon thermal expansion also changes sign, as commonly observed in hexagonal layered crystals. These two effects may be connected through subtle changes in the phonon spectrum at Tc.