[60 pts] In a gas of free and independent electrons in three-dimensions, the one-electron levels are specified by the wave vector
k
and spin kuantum number
s
with the energy given by
E(k)=(ℏ^(2)k^(2))/(2m)
. At zero temperature, the Fermi energy
E_(F)
can be defined in a way that the levels with
E(k)<=E_(F),(E(k)>E_(F))
are occupied (unoccupied). (e) [10 pts] To compute the heat capacity
C=\gamma T
, the specific heat should be multiplied by the volume of the system. Suppose that a mole of free electron metal contains
ZN_(A)
conduction electrons (
Z
is the valence and
N_(A)
is Avogadro's number). Calculate
\gamma
using
R=k_(B)N_(A)=8.314
joules/(mole
,K
calories/(mole K) and
(E_(F))/(k_(B))=10000K
and
Z=3
. Compute
\gamma
in units of
(J)/(molK)
and round up to two significant figures. (f) [5 pts] In the presence of external magnetic field
H
, suppose that the energy of an electron with the momentum
k
whose spin is parallel (antiparallel) to
H
is given by
E_(+)(k)=E(k)-\mu _(B)H
E_(-)(k)=E(k)+\mu _(B)H
. What is the relevant
g
-factor? (g) [5 pt] Since the magnetic field induces just a constant shift of single particle energies, one can define the density of states for electrons with the spin parallel (antiparallel) to
H
as
g_(+)(E)=(1)/(2)g(E-\mu _(B)H)(g_(-)(E)=(1)/(2)g(E+\mu _(B)H))
and the particle density of each species is given by
n_(+-)=\int dEg_(+-)(E)f(E)
satisfying
n=n_(+)+n_(-)
. When the Zeeman energy is much smaller than the Fermi energy, one can assume that
g_(+-)(E)=(1)/(2)g(E+-\mu _(B)H)=(1)/(2)g(E)+-(1)/(2)\mu _(B)Hg^(')(E)
. Using this approximation, find the chemical potential of the system. (Note the the chemical potential is
\mu
when
H=0
.) (h) [10 pts] The magnetization density is given by
M=-\mu _(B)(n_(+)-n_(-))
.