Superconductors,asthenamesuggests,areconductorsthatdonotdissipateenergyafterpassingacurrent.AftertheDutchscientistOnnesdiscoveredthesuperconductivityofmercuryin1911,peopleonlychangedthetemperatureinthefollowingseventyyears.Itwasincreasedto23K(aboutminus250°C).InearlyMarch2001,Japanesescientistsreportedthatthebinarymaterialmagnesiumdiboride(MgB2)exhibitedsuperconductingpropertiesatabout39K.TheoreticalcalculationsshowthattherearemorethanoneenergybandsacrosstheFermisurfaceinmagnesiumdiboride,andtheinstabilityoftheFermisurfacecausedbyelectro-acousticcouplingmaycompletelycreateanenergygapattheFermisurfaceofthetwoenergybands!Thisiscompletelydifferentfromalltraditionalsuperconductors.Theimagesofthetwoenergygapswerelaterwidelyconfirmedbyexperimentsofspecificheat,nuclearmagneticresonance,electrontunnelingspectroscopy,andangle-resolvedphotoelectronspectroscopy.Howthetwoenergygapsareformedandhowitaffectsthesuperconductingpropertiesisahotspotinthestudyofmagnesiumdiboridesuperconductors.Magnesiumdiboridesuperconductorshaveimportantapplicationsinelectricity,magnetism,andheat.
