# Tagged Questions

Fermions are particles with an intrinsic angular momentum (i.e. spin) equal to a "half integer" number of fundamental units: $\frac{(2n+1)}{2} \hbar$ for integer $n$. Fermions are required to be in a quantum state that is globally anti-symmetric, which leads to the Pauli Exclusion Principle barring ...

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### Majorana fermion [on hold]

I know that in condensed matter physics Majorana fermion is neutral and one fermion can be split into two Majorana fermions and vise versa. My question is charge. Two neutral particles can merge into ...
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### Chemical Potential as a function of Temperature

I have considered an ideal fermi gas. Then, we can obtain an expression for chemical potential as a function of Temperature. I want to understand the physical significance to it or what it really ...
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### What is the form of the kinetic energy operator on a one-dimensional (real space) lattice? (In second quantization)

I'm trying to figure out how one would write down the Hamiltonian of a free fermion system (eventually in second quantization) on a one dimensional lattice and I'm having trouble both coming up with ...
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### What is the difference between Fermi level and Fermi edge?

Just as in title: What is the difference between Fermi level and Fermi edge? My friend makes some research about XPS and he encountered this term. He knows what is Fermi level, but never heard about ...
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### Showing phase change for fermions

When discussing identical particles books often use that the states are eigenstates of the permutation operator: $P_{ij}|\psi\rangle = \lambda |\psi\rangle$ for bosons this is easy to see if I use ...
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### Can bosons that are composed of several fermions occupy the same state?

It is generally assumed that there is no limit on how many bosons are allowed to occupy the same quantum mechanical state. However, almost every boson encountered in every-day physics is not a ...
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### Current Status of the Monte Carlo Sign Problem

I've been reading about the Monte Carlo sign problem, and I am a little confused about its current status. Specifically, after reading this post When is the "minus sign problem" in quantum ...
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### The analytical result for free massless fermion propagator

For massless fermion, the free propagator in quantum field theory is \begin{eqnarray*} & & \langle0|T\psi(x)\bar{\psi}(y)|0\rangle=\int\frac{d^{4}k}{(2\pi)^{4}}\frac{i\gamma\cdot k}{k^{2}+i\...
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### What does it mean that a Cooper pair behaves as a boson but respects the obligations of fermions?

I refer to the fact that it has integer spin, but antisymmetric wavefunction. How is this possible?
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### Spontaneous symmetry breaking of a spinor / vector field [duplicate]

Why does SSB deal only with scalar fields and not with fermion or vector fields? My professor told me that it's closely related to the Lorentz invariance of the theory, but I don't understand at all ...