ITMO University physicists have demonstrated that electrons can emit microwave radiation photons even without a magnetic field, a phenomenon considered impossible under classical physics. The team’s calculations generalize the work of Lev Landau, who previously showed electron motion is quantized in a magnetic field, by examining behavior at the field’s edge. Researchers focused on how changing an electron’s wave properties, essentially “twisting” them, can lead to photon emission, with implications for improving particle accelerators and microscopes.
“An interesting aspect of our work is that it considers several geometric effects,” said Igor Shenderovich. “We were able to connect the radiation produced by the electron to the geometry of its quantum state.”
Twisted Electrons Radiate Photons Despite Absence of Magnetic Fields
Electrons confined to areas between magnetic lenses can emit microwave radiation photons despite the locally zero magnetic field, a result challenging classical physics expectations. ITMO University physicists demonstrated this emission through calculations focused on electron behavior at the edges of magnetic fields, generalizing Landau’s theory of electron motion in a magnetic field. Landau previously showed electrons move in discrete steps called Landau levels; this new research examines electron motion in non-uniform fields.
The team’s modeling considered electrons passing through multiple magnetic lenses, devices used to focus beams and alter electron wave shapes into complex structures. These electrons then enter regions between magnets where the magnetic force is negligible, a condition where photon emission shouldn’t occur according to established energy conservation laws. Calculations reveal that the twisting of the electron’s wave properties is key to this unexpected radiation.
The study, published in Physical Review A, builds on the known concept that electrons possess wave properties, radiating only when disturbed from a flat wave state. By accurately describing twisted electrons in conditions mirroring real-world experimental setups, the team provides a more nuanced model for these devices. The research suggests that manipulating an electron’s wave function, essentially “twisting” it, can induce photon emission even without a traditional magnetic force.
An interesting aspect of our work is that it considers several geometric effects. We were able to connect the radiation produced by the electron to the geometry of its quantum state and its evolution as it passes through the magnetic system. This means that we were able to demonstrate that it’s a geometric effect and its parameters are determined, among other things, by the location and setup of magnetic lenses.
Igor Shenderovich, a member of the team and a researcher at ITMO’s Faculty of Physics
Non-Uniform Magnetic Fields Generalize Landau Levels for Real Instruments
Electrons can emit photons even where magnetic fields are absent, a finding that challenges classical physics and expands the applicability of Landau levels to practical instruments. Researchers from ITMO’s Faculty of Physics detailed how electrons “twist” to produce this radiation, a phenomenon previously considered impossible without a magnetic force acting upon them. This emission occurs at the edges of magnetic fields created by coils commonly used in particle accelerators and electron microscopes, where field strength diminishes.
The team’s modeling accounts for non-uniform magnetic fields. The physics of electrons in a uniform magnetic field has been established for a considerable time. The Soviet physicist Lev Landau had shown that the motion of an electron in such a field is quantized; it permits only discrete states. This means that the electron does not move arbitrarily, but transitions from one level to another, as if climbing a set of steps.
These states are called Landau levels. However, this theory describes electron motion under the conditions of an ideally uniform magnetic field, which in reality requires special conditions. In real experiments involving particle accelerators or electron microscopes, the field is always significantly non-uniform, meaning the simplified Landau model is not suitable for describing them.
In these devices, the field is formed by separate magnetic coils, inevitably changing along the trajectory of electron movement; the field’s effect is stronger inside the coils and is absent between them. Magnetic coils focus electrons much like lenses focus light, but the resulting magnetic field isn’t consistent throughout the system.
By accurately describing how electrons behave, specifically how their wave properties are altered or “twisted”, in these non-uniform conditions, the ITMO physicists provide a more realistic model for existing technologies. This generalized understanding allows for more precise control and optimization of electron beams in both particle accelerators and advanced microscopy techniques, potentially improving resolution and efficiency.
This work is important primarily for fundamental physics. It helps understand how stable and controllable structured electron states are under conditions close to those of real laboratory setups. We were able to describe how a nonuniform field affects the life of an electron, which brings us one step closer to realism.
Stanislav Baturin, the head of the study and a senior researcher at ITMO’s Faculty of Physics
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