text: Related to the Fermi energy, a few useful quantities also occur often in modern literature.
  The Fermi temperature is defined as , where  is the Boltzmann constant. The Fermi temperature can be thought of as the temperature at which thermal effects are comparable to quantum effects associated with Fermi statistics. The Fermi temperature for a metal is a couple of orders of magnitude above room temperature. Other quantities defined in this context are Fermi momentum , and Fermi velocity , which are the momentum and group velocity, respectively, of a fermion at the Fermi surface. The Fermi momentum can also be described as , where  is the radius of the Fermi sphere and is called the Fermi wave vector.
  Note that these quantities are not well-defined in cases where the Fermi surface is non-spherical.