Questions tagged [quantum-tunneling]

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

Filter by
Sorted by
Tagged with
2
votes
0answers
103 views

Validity of the thin wall approximation

Inspired by the question How can I understand the tunneling problem by Euclidean path integral where the quadratic fluctuation has a negative eigenvalue?, I decided to come back to the first paper by ...
15
votes
2answers
337 views

Physical intuition for the Wilczek-Parikh tunneling picture of Hawking radiation

There's a naive pop-sci explanation of Hawking radiation, where a particle-antiparticle pair is produced just inside the event horizon. The particle with positive energy tunnels out and escapes, while ...
0
votes
2answers
73 views

Why can't the probability distribution of a quantum particle tunnelling be normalized?

Consider a quantum particle moving in the $x$- direction and hitting a wall of higher energy than it has. Classically, the particle cannot pass through the wall. Quantum mechanically, it can. Let $u(...
1
vote
0answers
46 views

How to derive the Gamow complex energy?

Consider the following potential It was shown how to derive the complex energy (near the ground energy) of a resonance in the left well from the Euclidean path integral by Callan and Coleman, see ...
1
vote
1answer
444 views

Quantum Tunneling, Superposition, and The Uncertainty Principle

After looking through various papers and articles on explanations of quantum tunneling I've been left wondering about one thing. I've read explanations of tunneling as an affect of a particles wave ...
0
votes
0answers
23 views

With such a low mass, how do enzymes use quantum tunneling to lower the activation energy in a reaction

The Sun uses quantum tunneling to create nuclear fusion, but only can achieve this through it's large mass. So how can enzymes in our body achieve this feat?
0
votes
0answers
13 views

How do enzymes use quantum tunneling (also, please use relatively simple vocabulary)? [duplicate]

I already know how the Sun uses quantum tunneling to create nuclear fusion, but can't apply it to enzymes. Also, since I'm only in eighth grade, please use relatively simple language. Thanks!
2
votes
0answers
59 views

How is the needle/tip of an STM actually made?

I was wondering how the needle/tip of an STM is made. Any links would be also great, I couldn't find any.
-1
votes
1answer
224 views

Dirac Delta potential

As we know a particle in attractive Dirac delta potential has discontinuity in the derivative of its wavefunction. I have two questions in this regard: Can a second order differential equation be ...
1
vote
1answer
89 views

How a tunnelled wave has the same energy even when the amplitude is lower

As I know that amount of energy carried by a wave is related to the amplitude of the wave than how in quantum tunnelling, tunnelled wave have the same energy even they have lower amplitude. I am ...
0
votes
1answer
150 views

Calculating the probability of transmission of a wave function between two delta distributions

Given is the potential :$V(x) = \frac{-\hbar^2}{m}D\delta(x+a) - \frac{-\hbar^2}{m} D\delta(x-a)$ with $a >0$ and $ D > 0$. A stream of particles from the positive $x$-axis are falling towards ...
0
votes
1answer
235 views

Chances of tunneling increased at low temperatures? [closed]

I have been giving a formula which states that the wavelength increases when the temperature decreases. When I plug this into the formula for the wavelength of Broglie, I get that my momentum ...
0
votes
1answer
103 views

Quantum Tunneling

Does Quantum tunneling prove there is a chance of big bang after the heat death of the universe? I mean how can we say it can produce another Big Bang in some years.
-1
votes
1answer
168 views

Quantum tunnelling near the speed of light [closed]

Given a particle travelling very close to the speed of light encountering a barrier, is it possible for the particle to exceed the speed of light by tunnelling forward in the direction of motion ...
0
votes
1answer
90 views

Probability, tunnelling and transmission ratio [closed]

This question is about tunnelling. It is from Physics for the IB diploma book. The question introduces this graphWhere it is said the graph does not take reflected electrons into account and that the ...
2
votes
1answer
54 views

Specifics of the current flow in a tunnel diode

Those are two diagrams depicting current flow along with equivalent band diagrams form two different textbooks. I believe one first one is resonant diode and second is tunnel diode only. From the ...
0
votes
1answer
236 views

Rectangular Potential Barrier: Particle stuck in Barrier

I am thinking about a problem in quantum mechanics. Given a rectangular potential barrier, say the potential $U(x) = V$ for $0 < x < L$ and $U(x) = 0$ otherwise, I found the solution for the ...
1
vote
0answers
31 views

Will the electrons flowing in a metal wire come out of it and even through non conducting insulation outside it due to quantum tunneling?

Lets imagine that electrons are passing through a conducting wire. According to quantum mechanics , each electron is in form of wave function . Does that wave function have a value above 0 even ...
0
votes
1answer
238 views

Meaning of wave function which is in inside of the potential wall? [duplicate]

In particle in square potential barrier problem, we can easily find that some probabilities exist which express how many particles can go beyond of the potential wall. So my question is that, can we ...
3
votes
1answer
270 views

A microscopic derivation of the Josephson effect

It is a little bit surprising to me that it seems hard to find a detailed, microscopic derivation of the Josephson effect. Generally, you see a hand-waving derivation based on the macroscopic ...
2
votes
0answers
105 views

Is it possible the opposite of tunneling?

In tunneling we have particles of energies $E<V$ going through barriers of potential $V$. Can we get particles of energies $E>V$ get reflected by these barriers of smaller potentials?
1
vote
0answers
66 views

Value of E1 or E2 in tunnelling diode current

I am trying to understand the meaning of the value E1,E2 in a tunnelling current expression derived in the following paper. http://aip.scitation.org/doi/pdf/10.1063/1.1735965 A more succinct overview ...
1
vote
0answers
52 views

What is the probability of a person quantum tunneling? [duplicate]

I understand that it has been shown that small particles can quantum tunnel to just about anywhere in space (with decreasing probability the further out they go) since they all act as waves when they ...
2
votes
2answers
266 views

Finding classical action in tunneling problem

In QM: I am trying to show that the minimum action for a classical path going between two potential wells (centered at $\pm L$) in a dbl-well potential is $$S_{classical} = \int_{-L}^{L} dx' \sqrt{...
1
vote
1answer
96 views

Would a quantum tunneling cable be possible?

I watched a spacetime video on youtube: https://www.youtube.com/watch?v=-IfmgyXs7z8 talking about how because of uncertainty, photons (and some small particles) can tunnel very small distances ...
1
vote
1answer
153 views

Can quarks tunnel out of a proton? Can a virtual electron tunnel away from its antiparticle?

I know that particles can tunnel through an impassable barrier. But what happens if a quark tunnels out of a proton? Has that ever been observed? And what about virtual particles?Can they tunnel away ...
1
vote
0answers
34 views

Landauer's formula with non-reciprocal tunneling probability

The Landauer's formula for ballistic transport in a mesoscopic conductor is often derived by assuming the transmission probability of the channel follows reciprocity symmetry, i.e. $I \propto \int M(...
-2
votes
1answer
258 views

Quantum tunnelling in semiconductors

Is quantum tunnelling is possible in a semiconductor (that is on either sides of depletion region)
4
votes
2answers
313 views

Why is the WKB tunneling amplitude a non-perturbative result?

The tunneling amplitude obtained from WKB aprroximation is given by $$|T(E)|=\exp\Big\{-\frac{1}{\hbar}\int\limits_{x_1}^{x_2}dx[2(V(x)-E)]^{1/2}\Big\}[1+O(\hbar)]$$ where $x_1$ and $x_2$ are the ...
4
votes
2answers
153 views

What sets the half life of unstable nuclei/nucleons?

A chemist friend asked me what sets the half life for free neutrons, unstable nuclei, etc. He said in chemistry half lives of molecules can often be calculated based on concentrations and molecular ...
1
vote
1answer
184 views

Quantum Tunnelling with Delta Potential

I'm trying to create an animation of Quantum Tunnelling like this one. I've been learning some QM on my own, so please forgive and correct any mistakes. I considered the potential barrier $\alpha \...
0
votes
2answers
44 views

Could one extract light out of a black hole via evanescent waves?

The Schwarzschild radius of a black hole is a classical barrier for light from inside of a black hole. But we know from electromagnetic waves and quantum mechanics that classical barriers can be ...
3
votes
1answer
189 views

What are good ways to check the validity of code to simulate the time-dependent Schrödinger equation?

Recently, I've made some code that can do simple quantum mechanics simulation as written in the title. I wanna check if this code correctly solves time-dependent Schrödinger equation and satisfies ...
-1
votes
1answer
285 views

Can quantum tunneling cause a particle to travel instantaneously across a distance essentially teleporting it? [closed]

Can quantum tunneling essentially teleport subatomic particles?
1
vote
0answers
40 views

Is transition between field configurations a tunneling process?

I'm considering D=1+1 kink solution here. Given a D=2 theory with $\mathbb{Z}_2$ symmetry, there are 4 different mappings (or 2 distinct sectors---trivial and kink) from spacetime manifold (or just a ...
4
votes
0answers
87 views

What happens when there are different classical trajectories before and after Wick rotation? [duplicate]

Recently I read the path integral of double well tunnelling. I am puzzled about the Wick rotation calculation. For example, I choose potential like $V(x)=(x^2-1)^2$ and Lagragian $L= \frac{1}{2} \dot ...
1
vote
0answers
124 views

Confusion about quantum tunneling through potential energy vs quantum tunneling through energy spectrum

It seems like that the drawing above describes the "energy spectrum" of a (final) hamiltonian. However, whenever we talk about quantum tunneling, we describe it as traversing through some kind of ...
1
vote
1answer
211 views

Black dwarf Iron formation through quantum tunneling

In a recent Kurzgesagt video about black dwarfs, it mentions that over extremely long periods of time, it may be possible for black dwarfs to slowly transform (from degenerate matter I'd assume) into ...
1
vote
1answer
849 views

Why doesn't an electron lose energy when tunneling?

Through my classwork I have learned that an electron will not lose energy when it is tunneling. However, I am having a hard time understanding why. From what I understand, as soon as the electron ...
1
vote
0answers
406 views

Physical interpretation of particle in classically forbidden region

Consider a stream of particles (a plane wave) with energy $E$ incident on a potential barrier with height $V_0 > E$. Mathematically this leads to an exponential decay of the probability of ...
4
votes
2answers
566 views

Macroscopic quantum phenomena and tunneling

Wikipedia's article on macroscopic quantum tunneling says Quantum phenomena are generally classified as macroscopic when the quantum states are occupied by a large number of particles (typically ...
3
votes
0answers
79 views

Why can quantum tunnelling be handled as a static problem? [duplicate]

Quantum tunnelling is a process that can happen in quantum mechanics but is forbidden in classical mechanics. Roughly speaking, a particle can possibly escape from a potential well or penetrate into a ...
13
votes
2answers
870 views

How to understand “analytical continuation” in the context of instantons?

Since this is a subtle and interesting question to me. I will give a rather detailed description. I hope you can keep reading it and find it interesting too. For simplicity, in the following I will ...
0
votes
0answers
168 views

Quantum mechanics particle beam incident on a step barrier

I have been confused several times by one case when considering particles in wells/with barriers in quantum mechanics, and I keep sweeping it under the carpet because I spend a very long time trying ...
1
vote
1answer
664 views

Significance of imaginary momentum in the finite potential well

In the case of the finite potential well, when the particle enters the classically forbidden region its wavenumber, $k$ is imaginary. However $k=\frac{2\pi}{\lambda}=\frac{p}{\hbar}$ so we get an ...
1
vote
2answers
350 views

Quantum mechanics: Wave vector is zero?

I am learning about basic quantum mechanics and am considering the time independent Schrodinger equation in 1D, which reduces to a second order ODE: $\frac{d^2}{dx^2}\psi (x)+[E-V(x)]\psi (x)=0$ Now ...
2
votes
0answers
136 views

Where is quantum plasticity theory?

Plasticity theory (the theory of irreversible deformations) is in the world of engineering, but not in the world of Theoretical Physics is my opinion. It is therefore an entirely classical theory that ...
3
votes
1answer
96 views

Relation of tunneling and adiabatic quantum computation

This is a post-question of Question about tunneling diagram in adiabatic quantum computation. Since adiabatic quantum computation essentially tries to evolve the system by keeping it on the ground ...
1
vote
1answer
73 views

Energy of a particle

When a particle such as an electron borrow energy to overcome a physical barrier, ( according to Heisenberg principle ) that energy has to be returned after a short while. Since total or a part of the ...
3
votes
2answers
247 views

Quantum Mechanics Tunneling

My understanding is that QM tunneling tells us how likely it is that a photon, electron, etc. will make it through a barrier. In layman's terms, is this true/correct?