Field Emission and Quantum Tunneling: A Window into Fundamental Problems of Quantum Mechanics ✛ ✎ ✦

Original: "Field emission tunnelling as a window onto fundamental issues in quantum mechanics"
· Richard G. Forbes
arXiv:2505.00872v4 · 2025-05-01 · arXiv non-exclusive · independent analysis · 3 min
How field-induced electron emission from a sharp tip sheds light on wave function interpretation, the limits of quantum mechanics, and even the nature of the arrow of time.

Context

Field electron emission is one of seven historical paradigmatic examples of quantum tunneling, predicted as early as 1928. Today, these effects underpin technologies ranging from atom-probe tomography to lightning protection of spacecraft. However, as the author's half-century experience shows, fundamental gaps remain in the theory, related to the interpretation of the wave function and accounting for many-body interactions. Even Schrödinger initially considered the wave function a description of a real matter distribution but was forced to abandon this view under critical pressure.

Methods

The author critically analyzed two main approaches to calculating the tunneling emission rate: the tunneling integral method (originally developed for the Schottky–Nordheim barrier, see formula) and the overlap integral method, dating back to Oppenheimer's work. Comparison was based on experimental data from field ion microscopy—images of tungsten facets and carbon nanotubes. To improve accuracy, a recently introduced special mathematical function vFD(x) and a formulation through amount of substance within the International System of Quantities (ISQ) were used, eliminating conceptual errors associated with the point-electron representation.

Results

It is shown that the tunneling integral approach qualitatively explains the contrast observed in a field ion microscope: atoms at the corners of a crystal facet glow brighter due to local field enhancement and displacement of the critical surface. Meanwhile, the overlap integral method cannot even predict the correct direction of contrast change. Both approaches remain incomplete: neither includes a proper account of the final-state density in both contacting media. A fundamental paradox is also identified: why the front of an electron emerging from a barrier does not detach from its 'tail' under a strong electrostatic field.

Implications

An alternative view of the wave function interpretation is proposed: its squared modulus, multiplied by the fundamental atomic amount of substance (1 electron), gives the concentration of 'electron matter' in space. This resolves the negative kinetic energy paradox and questions the standard formulation of the uncertainty principle as a limitation on simultaneous measurement of position and momentum. Instead, the author proposes a principle linking the electron's minimum kinetic energy to the length of its localization region.

Future development

In the coming years, a key task will be the direct experimental verification of the image formation mechanism in a field electron microscope. Advances in ultrafast laser technology give hope for 'filming' the tunneling process. Most intriguing is the possibility of extending the refined theory to biological systems: for example, proton tunneling in DNA could be responsible for mutations, and the behavior of helium ions—for radiation damage. This would open the way to quantum biology and even quantum botany.

Impact

Revising the foundations of tunneling theory will affect not only surface physics and nanoelectronics but also models of electrical breakdown, medical X-ray sources, and electric propulsion systems for spacecraft.

Next steps

Immediate steps: experimental verification of the irreversibility of tunneling path choice in many-electron systems; development of a universal formalism combining the tunneling integral and overlap integral, taking into account the real band structure; quantum-mechanical modeling of emission from carbon nanotubes for direct comparison with bond images.

Key open problems

The discussed difficulties are directly related to unresolved problems of quantum mechanics: the measurement problem, wave function interpretation, and the emergence of quantum decoherence. The author's proposal to abandon the point electron echoes the ideas of David Bohm and John Bell, but does not require hidden variables. The statistical irreversibility of tunneling path choice provides a simple mechanism for the arrow of time—an alternative to traditional explanations via decoherence.

The knowledge machine's view

This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.

What the work does

This study presents a critical analysis of two methods for calculating tunneling emission—the tunneling integral and the overlap integral—based on experimental data from field ion microscopy. It is shown that the tunneling integral approach qualitatively explains the observed contrast, whereas the overlap integral method fails to predict even its direction. An interpretation of the squared modulus of the wave function as the concentration of 'electron matter' is proposed, which calls into question the standard uncertainty principle and resolves the paradox of negative kinetic energy.

Where its strength is

The strength of this work lies in combining half a century of experimental experience with a consistent reexamination of foundational concepts: the rejection of the point-like electron and the reformulation of the uncertainty principle are grounded in specific observable effects in field ion microscopy, not in abstract arguments.

Where it could go next

  • The interpretation of the wave function as distributed 'electron matter' resonates with the idea that quantum objects may exhibit properties that depend on the observational context. Nearby in the archive, there is a discussion of how 'observation' affects the operation of a quantum engine—it might be interesting to see how the connection between measurement and system dynamics is treated there.based on: Quantum Engines Powered by a Look arXiv:2510.22394

Worth trying

  • Test whether the proposed interpretation of the wave function can quantitatively describe the intensity distribution in atom probe tomography for materials with known electronic structure.
  • Compare the paradox of the electron's 'non-detaching front' with models of radiation from charged black holes, where the question of maintaining the integrity of an object in a strong field also arises.

Why this may matter

If the revision of the concept of 'electron position' proves productive, it could impact not only the theory of field emission but also the interpretation of measurements in any systems with strong fields, including astrophysical ones.

The image of chemical bonds in a five-membered carbon ring (Fig. 1) was obtained at room temperature with a magnification of about 100,000,000 times. That's like examining a cherry the size of Earth and seeing its pit! And the brightest atom in the ion image of tungsten (Fig. 3)—the corner one — shines brighter because a larger positive charge accumulated on it due to geometry, and the local field pulls electrons from the gas more efficiently.

The idea that an electron, tunneling through a barrier, behaves like an octopus squeezing through a crack, evokes the scene from Arthur C. Clarke's '2001: A Space Odyssey,' where astronaut Bowman passes through the stargate, undergoing an incomprehensible transformation. The concept of a distributed 'material entity' resonates with the image of the sentient ocean in Stanisław Lem's 'Solaris'—an ocean simultaneously present in many points of space.

M(\phi,F,z)=\phi-eFz-\frac{e^{2}}{16\pi\epsilon_{0}z}
Difference between the electron's potential energy and its normal kinetic energy at distance z from the surface; ϕ is the work function, F is the field strength.
D\approx\exp\left[-\sqrt{\frac{8m_{e}}{\hbar^{2}}}\int_{z_{1}}^{z_{2}}M^{1/2}(\phi,F,z)dz\right]
Barrier transparency coefficient, where the integral is taken between classical turning points z1 and z2.
\Psi_{n}(\mathbf{r})\Psi_{n}^{*}(\mathbf{r})=n_{1}\psi(\mathbf{r})\psi^{*}(\mathbf{r})
Electron matter density distribution; n1 = 1 electron is the fundamental unit of amount of substance.

Key numbers

  • emitter tip radius: ~100 nm and less
  • field during field emission: a few V/nm
  • field during field ionization: 20–60 V/nm
  • FIM experiment temperature: ~80 K
  • field electron microscope magnification: ~100,000,000×
Scientists
George GamowLeo EsakiYakir AharonovDavid BohmMichael BerryRobert Hooke
Concepts
quantum tunneling field theory Quantum Field electrolyte transport electron transition transition Einstein's photoelectric equation energy barrier emission fundamental physics electron energy electromagnetism magnetic flux work tunnel junction Faraday's law of electromagnetic induction fermion photon classical physics Yang-Mills equation