Authors:	Drozdov, Alexander
Title:	Superconductivity in hydrogen-rich materials at high pressures
Online publication date:	15-Jul-2016
Year of first publication:	2016
Language:	english
Abstract:	A room temperature superconductor is probably one of the most desired systems in solid state physics. The highest critical temperature (Tc) that has been achieved so far is in the copper oxide system: 133 kelvin (K) at ambient pressure ([82]Schilling et al. 1993) and 160 K under pressure ([42]Gao et al. 1994). The nature of superconductivity in the cuprates and in the recently discovered iron-based supercondutor family (Tc=57 K) is still not fully understood. In contrast, there is a class of superconductors which is well-described by the Bardeen, Cooper, Schrieffer (BCS) theory - convetional superconductors. Great efforts were spent in searching for high-temperature (Tc > 77 K) conventional superconductor but only Tc = 39 K has been reached in MgB2 ([68]Nagamatsu et al. 2001). BCS theory puts no bounds for Tc as follows from Eliashberg’s formulation of BCS theory. Tc can be high, if there is a favorable combination of high-frequency phonons, strong electron–phonon coupling, and a high density of states. It does not predict however in which materials all three parameters are large. At least it gives a clear indication that materials with light elements are favorable as light elements provide high frequencies in the phonon spectrum. The lightest element is hydrogen, and Ashcroft made a first prediction that metallic hydrogen will be a high-temperature superconductor ([6]Ashcroft 1968). As pressure of hydrogen metallization was too high (about 400-500 GPa) for experimental techniques then he proposed that compounds dominated by hydrogen (hydrides) also might be good high temperature superconductors ([6]Ashcroft 1968; [7]Ashcroft 2004). A lot of the followed calculations supported this idea. Tc in the range of 50–235 kelvin was predicted for many hydrides. Unfortunately, only a moderate Tc of 17 kelvin has been observed experimentally ([27]Eremets et al. 2008) so far. A goal of the present work is to find a hydrogen-dominant material with higher Tc.
DDC:	540 Chemie 540 Chemistry and allied sciences
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 09 Chemie, Pharmazie u. Geowissensch.
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-4085
URN:	urn:nbn:de:hebis:77-diss-1000005734
Version:	Original work
Publication type:	Dissertation
License:	In Copyright
Information on rights of use:	https://rightsstatements.org/vocab/InC/1.0/
Extent:	90 Blätter
Appears in collections:	JGU-Publikationen