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visits member for 2 years, 10 months
seen May 29 at 18:08

Graduate Student - Experimental Condensed Matter Physics


May
18
accepted Evolution of Eigenstates when two spin systems are coupled
May
16
revised Evolution of Eigenstates when two spin systems are coupled
added 816 characters in body
May
16
comment Evolution of Eigenstates when two spin systems are coupled
Dear Rod, thanks for the detailed answer but I'm afraid that this is a bit too complicated for me. I thought it must be easier by making a few simplifications, e.g. we only care about the isotropic part of the coupling and assume ferromagnetic coupling. So let's say in this case I want to apply an external magnetic field B_z to the spin-1 system and the two spins are connected by $H = J * \vec{S_1} \cdot \vec{S_2}$. So our total Hamiltonian would be: $H = g\mu B_z*S_z + J * \vec{S_1} \cdot \vec{S_2}$. Can't I just take the tensorproducts of the individual operators and that's it?
Apr
15
revised Evolution of Eigenstates when two spin systems are coupled
added 149 characters in body
Apr
15
revised Evolution of Eigenstates when two spin systems are coupled
deleted 243 characters in body
Apr
15
asked Evolution of Eigenstates when two spin systems are coupled
Dec
16
awarded  Notable Question
Sep
24
awarded  Autobiographer
Aug
7
awarded  Popular Question
Nov
27
awarded  Popular Question
Oct
10
revised Operator that takes us from one density matrix to another?
deleted 5 characters in body
Oct
10
comment Operator that takes us from one density matrix to another?
Hello Mark, thanks for your comment! For 3): Yes, that was a typo, I meant $M_{ij} = <i|M|j>$. For 1) and 2): I admit, I am confused. Let's say we have a STM tip with a single atom at the end and a sample that has a single atom on the surface. Then these two atoms have a spin. If you bring them close enough they can interact (e.g. through the Kondo effect) while at the same time electrons "flow" through the STM from the tip atom to the sample atom. Im struggling to find a way to describe how the electron goes from one state into the other.I will probably write more details in my question tmrw.
Oct
10
asked Operator that takes us from one density matrix to another?
Aug
14
comment How is a Majorana fermion created when a s-wave superconductors is in proximity to a topological insulator (e.g. via an antidot)
Thanks, Looks like a great piece of work!
Aug
13
comment How is a Majorana fermion created when a s-wave superconductors is in proximity to a topological insulator (e.g. via an antidot)
Hello Lababidi, I hope you finished your thesis and had a successful defense! Is there a way to take a look at it?
Aug
12
comment Why does electricity need wires to flow?
Your analogy is good! But why do you assume that the ball will "fall" to the ground of the pool? Depending on the material, the ball can also just float on top of the water or stay somewhere in the middle and dive around. If you increase the voltage, then the air will get ionized and can also conduct electrons, therefore it only depends on the energies and materials involved, but your analogy still holds in terms of a potential field. Even in vacuum, if the energy is high enough, you can create electrons and positrons (pair production).
Aug
11
revised How to transform mechanical work into electrical energy without using piezoelectricity?
edited body
Aug
11
comment How to transform mechanical work into electrical energy without using piezoelectricity?
Bitte ;) und viel Erfolg!
Aug
11
answered How to transform mechanical work into electrical energy without using piezoelectricity?
Jul
19
comment Where does the Berry phase of $\pi$ come from in a topological insulator?
Now I found this argument from Shoucheng Zhang: $\gamma \rightarrow \gamma + 2\pi n$ is invariant because we take it mod 2. Now here's the next step I don't understand: Time reversal takes $\gamma \rightarrow -\gamma$ which is true for $\gamma = 0$ or $\gamma = \pi$.