Quantum lifetime
= Quantum lifetime
{title2=$\tau_q$}
The <quantum lifetime> determines the broadening of a single-particle spectral level by scattering. It need not equal the <momentum relaxation time>: small-angle scattering broadens levels while relaxing current weakly. A common Lorentzian broadening convention is a half-width $\Gamma=\hbar/(2\tau_q)$.