# Tagged Questions

Quantum tunneling is a classically-forbidden quantum effect that allows an bound object with energy less than the boundary to penetrate it with a small probability. A notable example is $\alpha$-decay

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### Mechanism for collapse of iron stars into black holes via quantum tunnelling

In the wikipedia page "Future of an expanding universe" it refers to the scenario of a future without proton decay. The page talks about how processes would lead to stellar-mass cold spheres of iron, ...
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### Why we can't use quantum tunnelling still in nuclear fusion where sun uses this trick of nature easily?

Sun haven't enough temperature to break down coulomb barrier between two protons to be fussed.But yet nuclear fusion occurs through quantum tunnelling process.So,why we can't use quantum tunnelling in ...
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### Scattering from a step potential barrier

Suppose a potential barrier of the form $$V(x) = \begin{cases} V_0 & x>0 \\ 0 & x<0 \end{cases}$$ Then, for energy $E$ such that $E < V_0$, we have that the transmission and ...
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### Tunnelling induced energy splitting

In 1D lattice, the energy splitting of the zero energy edge modes or Majorana fermion modes in the topological insulator seems to be due to the tunnelling between the modes at opposite ends. This ...
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### What does it mean to have a transmission coefficient 1.03*10^-3

I solved a potential barrier problem. E=4.5ev V0=5eV barrier width a=950pm The transmission coefficient came out to be 1.03*10^-3 I was wondering what this means? isn't the transmission probability ...
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### Applicability of wavefunction matching when Hamiltonian (not just potential) varies

A simple tunnelling calculation can be performed for a potential step by calculating the eigenfunctions for the Hamiltonian on either side of the step and matching the wavefunctions (and using ...
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### How to calculate tunneling current between two metals separated by a dielectric?

If I have two metallic electrodes (e.g. Al, Cr) separated by a dielectric (ε, d; e.g. SiO2), how can I calculate the tunneling current as a function of applied voltage?
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### What is the kinetic energy of a quantum particle in forbidden region?

I have read that if a particle is trapped in a finite potential well, it has a finite chance to tunnel out from it. Therefore, one can find a particle in a region where its potential energy is greater ...
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### How can quantum tunnelling lead to spontaneous decay?

I have never understood what measuring process (if any) is supposed to be continuously polling the quantum state of an unstable bound system subjected to decay via quantum tunnelling. The reason I ...
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### Quantum tunneling and the Gamow Factor

I've seen the equation for the probability of particles overcoming the Coulomb Barrier in the following form: $$P(E)=\exp\left[-\sqrt{E_G/E}\right]$$ Where I'm using the numerator $E_G$ as the ...
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### In semiconductor devices, why is quantum tunneling “fast”?

I'm reading up on semiconductor devices that rely on quantum tunneling, such as the tunnel diode and the TFET. The big advantage of these devices is apparently that "quantum tunneling is extremely ...
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### Klein tunneling in graphene including intervalley scattering

In calculations relating to Klein tunneling (in particular in graphene) I have seen the treatment of a "smooth" potential (on the scale of the Fermi wavelength) or the more typical treatment of a "...
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