# Matthias

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bio website location Germany age member for 2 years, 8 months seen May 22 at 0:06 profile views 92

Graduate Student - Experimental Condensed Matter Physics

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 May18 accepted Evolution of Eigenstates when two spin systems are coupled May16 revised Evolution of Eigenstates when two spin systems are coupled added 816 characters in body May16 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? Apr15 revised Evolution of Eigenstates when two spin systems are coupled added 149 characters in body Apr15 revised Evolution of Eigenstates when two spin systems are coupled deleted 243 characters in body Apr15 asked Evolution of Eigenstates when two spin systems are coupled Dec16 awarded Notable Question Sep24 awarded Autobiographer Aug7 awarded Popular Question Nov27 awarded Popular Question Oct10 revised Operator that takes us from one density matrix to another? deleted 5 characters in body Oct10 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 $M_{ij} =$. 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. Oct10 asked Operator that takes us from one density matrix to another? Aug14 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! Aug13 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? Aug12 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). Aug11 revised How to transform mechanical work into electrical energy without using piezoelectricity? edited body Aug11 comment How to transform mechanical work into electrical energy without using piezoelectricity? Bitte ;) und viel Erfolg! Aug11 answered How to transform mechanical work into electrical energy without using piezoelectricity? Jul19 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 $\gamma = \pi$.