Laser Field Reduces Quantum Tunneling by up to 50 Percent

A thorough investigation into the tunneling of Dirac fermions within a monolayer tungsten diselenide barrier, under both a static electrostatic field and laser irradiation, reveals key insights into quantum transport. Rachid El Aitouni and colleagues demonstrate that a linearly polarized laser field induces a Floquet sideband structure, sharply suppressing transmission and offering a new method to bypass Klein tunneling. This dynamic control, achieved through light-matter interaction, provides a pathway towards advanced optoelectronic devices, including flexible quantum filters and light-controlled nanoscale transistors.

Laser irradiation suppresses electron velocities and enables dynamic quantum control

Electron velocities in irradiated tungsten diselenide were reduced to approximately 300 times smaller than the speed of light, a dramatic decrease previously unattainable in this material. This suppression of velocity overcomes Klein tunneling, a quantum phenomenon where electrons bypass barriers irrespective of energy, which previously limited electron confinement and hindered device performance. By inducing a ‘Floquet sideband structure’, a series of additional energy states, interference effects were created that dynamically control electron transmission, allowing for the potential development of tunable quantum filters and light-controlled nanoscale transistors.

Increasing laser driving parameters expand the induced ‘Floquet sideband structure’, revealing a direct link between light intensity and the number of available energy states within the tungsten diselenide. The formation of Stark-like confined states, localized regions where electrons are trapped due to the light-matter interaction, intensified as the irradiated region broadened, enhancing control over electron behaviour. Büttiker analysis, a method for calculating conductance, revealed that interference between multiple Floquet channels sharply reduces the transmitted current, suggesting a pathway to actively ‘switch’ current flow.

Transmission remained possible even with the 300-fold reduction in electron velocity, but these findings currently rely on theoretical modelling and do not yet demonstrate consistent, scalable fabrication of functioning devices at room temperature. The technique offers a pathway towards advanced optoelectronic devices with unprecedented control over quantum transport. Realising practical devices, however, requires addressing the sensitivity of these effects to material imperfections and achieving scalable fabrication at room temperature.

Laser modulation of tungsten diselenide via Floquet engineering of band structure

This work centres on the application of the Floquet formalism, a mathematical framework used to analyse systems that evolve periodically in time. Consider a strobe light freezing a moving object into a series of still images; this formalism performs a similar function for electron behaviour. Shining a laser onto tungsten diselenide created a dynamic, time-dependent potential that fundamentally altered how electrons tunnel through barriers. These laser-induced modulations generate ‘Floquet sidebands’, essentially additional energy levels, which interfere with the electron’s wave function.

A monolayer of tungsten diselenide, a semiconductor with an inherent bandgap, underwent investigation using a static potential barrier and linearly polarised laser irradiation. The laser’s amplitude and frequency were key parameters in modulating electron flow, avoiding the need for additional constraints required in gapless materials like graphene. Applying the Büttiker approach allowed analysis of the time-dependent system, calculating transmission and reflection coefficients to determine conductance.

Laser control of electrons in tungsten diselenide challenged by material imperfections

This offers a new way to manipulate electrons within tungsten diselenide, a crucial step towards building smaller, faster electronics. Real-world materials invariably contain defects and impurities, raising a critical question: how sensitive are these laser-induced effects to imperfections in the material itself, and could these flaws disrupt the carefully engineered ‘Floquet sideband structure’ necessary for precise control. Establishing this key principle is possible even with calculations assuming perfect materials.

Light manipulation can dynamically control how electrons move through tungsten diselenide, a two-dimensional material with potential in future electronics. Understanding these fundamental interactions remains valuable regardless of material imperfections. Scientists continue to refine control over electrons in two-dimensional materials like tungsten diselenide using light, and this approach, employing ‘Floquet sideband structure’ to create new electron pathways, will likely underpin advances in nanoscale devices over the next decade, potentially beginning a new era of optoelectronic engineering.

Recent advances in manipulating light-matter interactions have enabled dynamically tunable electron behaviour in tungsten diselenide. Applying a laser field to this material induces ‘Floquet sidebands’, additional energy states which alter how electrons tunnel through potential barriers, overcoming the limitations of Klein tunneling, a quantum effect previously hindering electron confinement. This precise control of quantum transport opens possibilities for novel optoelectronic devices.

The research demonstrated that a laser field can dynamically control how electrons move through a monolayer of tungsten diselenide. This control arises from the creation of ‘Floquet sidebands’, which modify electron tunnelling and suppress transmission through barriers. By manipulating light, scientists achieved a mechanism to overcome Klein tunnelling, allowing for greater control over electron behaviour. The Büttiker approach facilitated analysis of this time-dependent system, calculating transmission and reflection coefficients to determine conductance.