Anomalous Thermal Expansion in Superconducting Mg1− Al B2 System. Palmisano, V., Agrestini, S., Campi, G., Filippi, M., Simonelli, L., Fratini, M., Bianconi, A., De Negri, S., Giovannini, M., Saccone, A., Fitch, A. N., Brunelli, M., & Margiolaki, I. Journal of Superconductivity, 18(5-6):737–741, 2005.
Anomalous Thermal Expansion in Superconducting Mg1− Al B2 System [link]Paper  doi  abstract   bibtex   
The thermal lattice expansion in the superconducting Mg1− x Al x B2 system (x = 0, 0.13, and 0.59) has been measured using high-resolution X-ray powder diffraction. An unusual large negative thermal expansion (NTE) appears for temperatures below T * = 60 K in the MgB2. The NTE effect increases in Mg0.87Al0.13B2 and disappears at high Al content in the Mg0.59Al0.41B2 where the temperature dependence of volume follows a standard Einstein model in the whole temperature range. The anomalous behavior of the thermal expansion provides a direct evidence in the physics of diborides for the relevance of the proximity to the 2.5 Lifshitz electronic topological transition where the Fermi surface of the σband changes from a two-dimensional (2D) to a three-dimensional (3D) topology.
@article{palmisano_anomalous_2005,
	title = {Anomalous {Thermal} {Expansion} in {Superconducting} {Mg}1− {Al} {B}2 {System}},
	volume = {18},
	issn = {1432-9840},
	url = {http://dx.doi.org/10.1007/s10948-005-0072-4},
	doi = {10.1007/s10948-005-0072-4},
	abstract = {The thermal lattice expansion in the superconducting Mg1− x Al x B2 system (x = 0, 0.13, and 0.59) has been measured using high-resolution X-ray powder diffraction. An unusual large negative thermal expansion (NTE) appears for temperatures below T * = 60 K in the MgB2. The NTE effect increases in Mg0.87Al0.13B2 and disappears at high Al content in the Mg0.59Al0.41B2 where the temperature dependence of volume follows a standard Einstein model in the whole temperature range. The anomalous behavior of the thermal expansion provides a direct evidence in the physics of diborides for the relevance of the proximity to the 2.5 Lifshitz electronic topological transition where the Fermi surface of the σband changes from a two-dimensional (2D) to a three-dimensional (3D) topology.},
	number = {5-6},
	journal = {Journal of Superconductivity},
	author = {Palmisano, V. and Agrestini, S. and Campi, G. and Filippi, M. and Simonelli, L. and Fratini, M. and Bianconi, A. and De Negri, S. and Giovannini, M. and Saccone, A. and Fitch, A. N. and Brunelli, M. and Margiolaki, I.},
	year = {2005},
	keywords = {lifshitz},
	pages = {737--741}
}

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