Can Quantum Tunneling Occur Through a Material Barrier?

In summary, the conversation discusses the concept of tunneling and whether it is possible for a person or an object to pass through a solid barrier. While popular explanations mention the possibility, the presenter clarifies that it is highly unlikely and would take longer than the age of the universe to witness. Tunneling is commonly seen in physics texts with barriers that are energy hills rather than solid walls. However, there are examples of tunneling through thin stacks of atoms, such as in a tunnel diode. The question is posed whether the wavefunction of a mesoscopic composite object can pass through a thin, massive composite object and show a measurable effect. The discussion also touches on the role of electrostatic forces in creating barriers.
  • #1
Swamp Thing
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A lot of popular level explanations introduce the idea of tunneling by saying that "in principle" a person in one room can "find themselves" in the next room, i.e. one can tunnel through a wall

Of course, the presenter then hastens to clarify that this is so unlikely that we would have to wait longer than the age of the universe in order to have some chance of witnessing a macroscopic tunneling event.

On the other hand, in physics texts we only see examples of tunneling where the barrier is an energy hill rather than a wall composed of atoms. The wavefunctipn has a non zero value beyond the potential barrier.

So my question is, is it at all possible for tunneling to happen through a material barrier? I'm thinking of, say, an atom or small molecule tunneling through a film that is one atom thick. (But assiming a scenario where classical diffusion would not occur). Would the wavefunction ooze through such a film?
 
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  • #2
Swamp Thing said:
A lot of popular level explanations introduce the idea of tunneling by saying that "in principle" a person in one room can "find themselves" in the next room, i.e. one can tunnel through a wall

Of course, the presenter then hastens to clarify that this is so unlikely that we would have to wait longer than the age of the universe in order to have some chance of witnessing a macroscopic tunneling event.

On the other hand, in physics texts we only see examples of tunneling where the barrier is an energy hill rather than a wall composed of atoms. The wavefunctipn has a non zero value beyond the potential barrier.

So my question is, is it at all possible for tunneling to happen through a material barrier? I'm thinking of, say, an atom or small molecule tunneling through a film that is one atom thick. Would the wavefunction ooze through such a film?
This effect (tunneling through thin stack of atoms) is known and even used in device called "tunnel diode".
 
  • #3
Thanks for the prompt reply. I did think of the tunnel diode before posting, but I had the impression that the barrier at the junction is still a potential barrier from the view point of an electron. After all, an electron is pretty free to move through a conductor or a doped semiconductor, and it is only the junction potential profile that stops electrons from wandering across. In some sense, the junction barrier seems to lack the "solidity" of a wall. And a free electron is inherently a part of the solid state structure of the diode, so it doesn't seem very amazing that it can tunnel across the junction.

But after thinking about your post for a while, I did realize that any "solid" barrier works only because of electrostatic forces. Considering a mesoscopic example -- a very thin insulating polymer film and, say, a heavy ion or small molecule. In this case, a classical path through the barrier would involve intermediate stages where the molecule would feel strong electrostatic forces that would try to push it back -- places where the potential energy would be locally high.

So my distinction between the tunnel diode and a brick wall was probably an arbitrary one, so thank you again for the reply.
 
  • #4
But there is still this nagging question in my mind. Are there examples where the wavefunction of a mesoscopic composite object passes through a large, thin, massive composite object, to an extent that it can show up as a measurable effect?
 
  • #5
Swamp Thing said:
in physics texts we only see examples of tunneling where the barrier is an energy hill rather than a wall composed of atoms

What do you think produces the "energy hill"?
 
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Related to Can Quantum Tunneling Occur Through a Material Barrier?

1. What is tunnelling through matter?

Tunnelling through matter is a phenomenon in which a particle, such as an electron or proton, is able to pass through a barrier or potential energy barrier that it would normally be unable to cross according to classical physics.

2. How does tunnelling through matter occur?

Tunnelling through matter occurs through the principles of quantum mechanics, where particles are described as waves with a certain probability of being found in a particular location. This allows for the possibility of a particle to exist on both sides of a barrier simultaneously, leading to the phenomenon of tunnelling.

3. What are the applications of tunnelling through matter?

Tunnelling through matter has several practical applications, such as in scanning tunneling microscopy, which allows for the imaging and manipulation of individual atoms and molecules. It is also used in semiconductor technology, where electrons can tunnel through thin barriers to create electronic devices.

4. Can tunnelling through matter be observed in everyday life?

While tunnelling through matter is a fundamental principle of quantum mechanics, it is not typically observed in everyday life due to the small scale at which it occurs. However, it is essential for many technological advancements and is observed in various experiments and phenomena at the atomic and subatomic level.

5. Are there any risks associated with tunnelling through matter?

There are no known risks associated with tunnelling through matter, as it occurs on a microscopic scale and does not have any significant impact on everyday life. However, further research is being conducted to fully understand the implications of this phenomenon in various fields of science and technology.

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