100% Fermi-dirac distribution 80% AmqeqoId 60% 40% <n>= e() 20% T+1 0% -0.2 -0.1 0 0.1 0.2 Energy (eV) For Metal Fermi energy N= 2 3π Er= 经_ 0.121hm2 2m 2m mFermi-dirac distribution Fermi energy 1 1 ( )/    Eu kB T e n 3 2 3 F k V N   2/3 2 2/3 2 2 2 2 0.121h ) 3 ( 2 2 n V m N m m k E F F       For Metal