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visits member for 2 years, 4 months
seen Jul 2 at 11:30

I'm an experimental condensed matter physicist, but I'm very curious about high energy physics as well.


Jul
2
awarded  Curious
Jul
2
asked Alignment of Fermi Levels between Metal and Insulator
Jun
5
comment Can the Berry Connection be derived from a metric?
Ok cool thanks. So if that's not true, my question still holds: Does a metric exist such that the Berry Connection is a Levi-Civita connection?
Jun
5
asked Can the Berry Connection be derived from a metric?
Jun
5
accepted What is curved in Berry Curvature?
Jun
5
comment Does electron-electron scattering contribute to resistivity?
So... Have we reached consensus in this debate? Or still in disagreement?
May
23
comment Does electron-electron scattering contribute to resistivity?
Thank you for the detailed response! I'm still somewhat confused. Even in the presence of electron-electron interactions, we have translational invariance, so the total momentum is a good quantum number. How do we reconcile Fermi liquid theory with the requirement that the total momentum of the system is conserved?
May
21
asked Does electron-electron scattering contribute to resistivity?
Apr
29
accepted Phase factor for nearest neighbor hopping in the Haldane Model
Apr
10
accepted Where does the phase difference come from in a Josephson Junction?
Apr
9
comment Where does the phase difference come from in a Josephson Junction?
I am beginning to understand now. So, if we tie both superconductors to a common voltage $V$, there will be no current? And from $\dot{\phi}=2eV/\hbar$, $\phi =2eVt/\hbar+C$. What determines the integration constant?
Apr
7
comment Where does the phase difference come from in a Josephson Junction?
I would have assumed that if we prepared two superconductors in the exact same way at the exact same time (of course, experimentally impossible), they would have the same phase. Or is that wrong? Is there something else that determines the initial phase?
Apr
7
comment Where does the phase difference come from in a Josephson Junction?
Thanks. What I meant to ask was: what determines the phase that the superconductor starts with? Is it completely random? If I take a superconductor, break it into two, will the Josephson current between them be zero at $V=0$ because they have the same phase?
Apr
7
comment Where does the phase difference come from in a Josephson Junction?
Thanks. This was well explained. Why must there be a current at $V=0$? Why not $I=0$?
Apr
6
asked Where does the phase difference come from in a Josephson Junction?
Mar
30
awarded  Tumbleweed
Mar
30
comment Why is the Gibbs Free Energy $F-HM$?
What do you mean the Legendre Transform leave the value of the function unaltered? It changes the value of the function by $-HM$.
Mar
30
comment Why is the Gibbs Free Energy $F-HM$?
The first half of my response is a proof that the Helmholtz Free Energy is minimized at equilibrium, and $E_2=T S_2$ comes from integrating the definition of temperature: $1/T=\partial S/\partial E$, modulo a constant. Note that a crucial part of this proof is $E=E_1+E_2$, or $V=V_1+V_2$ or $N=N_1+N_2$, something that we can't write for the magnetic case. It doesn't matter that $V=\infty$ because $dV_1=-dV_2$ is what is really important, and also $\mu=-T\partial S/\partial N$ covers non-conservation of particles.
Mar
27
comment Why is the Gibbs Free Energy $F-HM$?
Perhaps I need to be a little more explicit. If we couple a system (labeled 1) to a heat bath (labeled 2) we maximize the total entropy $S=S_1+S_2$. The total energy is conserved $E=E_1+E_2$. If we take the heat bath energy to be $E_2=T S_2$, then $S=S_1+E_2/T=S_1+(E-E_1)/T$. Maximizing $S$ is the same as minimizing $E_1-T S_1$, which is the Helmholtz Free Energy. You can do the exact same analysis for $PV$ and $\mu N$, and it doesn't really matter if particles aren't conserved and that $V=\infty$. However, how do you prove that $F-HM$ maximizes global entropy?
Mar
26
asked Why is the Gibbs Free Energy $F-HM$?