The Mermin-Wagner Theorem - Condensed Matter Theory Group
The Mermin-Wagner Theorem - Condensed Matter Theory Group
The Mermin-Wagner Theorem - Condensed Matter Theory Group
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
How symmetry breaking occurs in principle<br />
Actors<br />
Proof of the <strong>Mermin</strong>-<strong>Wagner</strong> <strong>The</strong>orem<br />
Discussion<br />
<strong>The</strong> Bogoliubov inequality<br />
<strong>The</strong> <strong>Mermin</strong>-<strong>Wagner</strong> <strong>The</strong>orem<br />
We now want to find out whether the isotropic Heisenberg model<br />
gives a spontaneous magnetization. <strong>The</strong> starting point is the<br />
Hamiltonian<br />
H = − <br />
JijSi · Sj − b <br />
S z i e −iK·Ri<br />
We are interested in the magnetization<br />
i,j<br />
Ms(T ) = lim<br />
B0→0 gJ<br />
µB<br />
<br />
<br />
i<br />
i<br />
e −iK·Ri 〈S z i 〉 T ,B0<br />
Andreas Werner <strong>The</strong> <strong>Mermin</strong>-<strong>Wagner</strong> <strong>The</strong>orem
Change language