Light-Gated Jacutingaite: A Floquet Route to Switchable Spin-Valley Filters

A new Floquet-materials preprint takes a material that is already famous in topological electronics—monolayer jacutingaite, Pt₂HgSe₃—and asks a practical control question: can light turn a tunnel barrier into a switchable filter for the spin and valley identity of electrons?

In “Floquet engineering of spin-valley selective transport in jacutingaite,” Otman Bouladiane, Kamal Azaidaoui, Clarence Cortes, David Laroze and Ahmed Jellal study a monolayer jacutingaite tunnel junction where only the barrier region is illuminated by off-resonant circularly polarized light while the leads remain undriven.¹ In the high-frequency limit, that periodically driven barrier behaves like an effective static Dirac Hamiltonian with a photon-dressed, valley-dependent mass term.¹

The important shift is from “light changes a material” to “light writes a selective transport rule.” In this proposal, the illuminated region can favor one valley, one spin direction, or the opposite choice when the knobs are changed.

The result belongs squarely in the Floquet-materials breakthrough category. It is not a battery, a heat engine, or a claim of over-unity energy production. Instead, it is about microscopic energy and information flow: if a low-dimensional conductor can route carriers by spin and valley using an optical drive, then future quantum-energy devices gain a new kind of gate—one based on time-periodic control rather than static wiring alone.

Why jacutingaite is a useful stage for Floquet control

Jacutingaite has attracted attention because its monolayer form has been discussed as a large-gap Kane-Mele quantum spin Hall platform.⁷ Quantum spin Hall materials are valuable because their topology can support edge channels whose spin and direction are linked, reducing ordinary backscattering channels in an idealized picture. The broader jacutingaite family also offers a chemically rich platform for topological phase transitions and transport studies.⁸

For non-specialists, the key point is that jacutingaite already carries several ingredients that Floquet engineers like: strong spin-orbit coupling, Dirac-like low-energy physics, and valley degrees of freedom. A valley is not a physical valley in space; it is a distinct energy minimum or momentum-space region in the electronic band structure. In two-dimensional materials, valleys can behave like an extra label for carriers, alongside charge and spin.

The proposed device: drive the barrier, not the whole sample

The new paper considers a tunnel junction: electrons approach a finite barrier region, scatter through it, and emerge into an undriven lead. The clever modeling choice is that only the barrier is irradiated. That matters because many Floquet experiments struggle with a whole-sample problem: a strong drive can create the desired dressed states, but it also heats and perturbs everything. A spatially confined driven barrier is closer to a device element: a light-gated section embedded between quieter regions.

In the authors’ high-frequency treatment, off-resonant circularly polarized light modifies the effective mass term in the Dirac Hamiltonian. Crucially, the modification has opposite signs in the K and K′ valleys.¹ The model also includes a staggered sublattice potential, written as V_z, and a substrate-induced exchange field, written as m_s, giving three major knobs: light amplitude, electrostatic or structural asymmetry, and magnetic proximity.

Once those knobs are set, the barrier transmits some spin-valley channels better than others. The finite width of the barrier produces Fabry-Pérot-like interference, meaning that transmission oscillates with the phase accumulated inside the barrier.¹ That is not merely a complication; it is also a design resource. In a wave device, length, phase and resonance can become control parameters.

What “switchable” means here

The most practical part of the proposal is not only that filtering appears. It is that the dominant spin and valley polarizations can be switched by changing the drive amplitude A₀, the staggered potential V_z, or the exchange field m_s.¹ In other words, the device is not just a static material with a fixed preference. It is a controllable selector.

This is a recurring theme in recent Floquet materials work. An August 2026 preprint on transition-metal dichalcogenide heterobilayers proposed that near-infrared to visible periodic driving could invert photon-dressed bands and create topological phases with Chern numbers up to ±2 and gaps on the order of 10 meV.² Another August 2026 paper studied linearly driven d-wave altermagnets, where rotating the polarization can swap spin sectors and reverse the Chern number.³ The jacutingaite work fits the same larger pattern: light is becoming a material-programming interface.

Static topological devices are fabricated into one operating point. Floquet devices aspire to make the operating point a setting—amplitude, polarization, frequency, phase, and geometry.

That vision is still early. The new jacutingaite paper is theoretical, and real devices would need to survive disorder, finite temperature, contacts, substrate roughness, pulse imperfections and heating. But theory at this stage has a useful role: it identifies which combinations of symmetry, material and drive should be worth the experimental expense.

Why this matters for quantum-energy research

Floquet.ca focuses on quantum energy, so it is worth being precise about the energy connection. A spin-valley filter is not an engine extracting work from a heat bath. It is a controlled scattering element. Its relevance is that energy technologies at the quantum scale increasingly depend on controlling which microscopic channels carry excitation, charge, heat or information.

In classical electronics, wasted power often appears as uncontrolled dissipation. In quantum devices, the equivalent problem can be more subtle: unwanted transitions, leakage into the wrong modes, backflow, dephasing, and heating from control fields. A Floquet barrier that favors selected channels could help separate useful flow from wasteful flow, especially in hybrid devices where topological, spin, valley and optical degrees of freedom meet.

The quantum-battery community is moving in a related direction. A July 2026 review on many-body spin-chain batteries emphasized the connection between continuous control and periodic Floquet driving as platforms for microscopic energy storage and work extraction.⁵ Although jacutingaite filters are a different class of device, the shared engineering problem is the same: time-dependent control must deliver useful functionality without depositing so much heat that the advantage disappears.

From Floquet filters to practical architectures

If this line of research matures, a realistic architecture might look less like a continuously blasted material and more like a circuit with local driven regions. One section could act as a spin-valley injector, another as a topological channel, another as a detector, and still another as a dissipative reset element. The light field would not be decoration; it would be part of the circuit logic.

That architecture would benefit from recent work on optical control in jacutingaite beyond the new transport paper. A 2025 preprint studied the Edelstein effect in optically driven monolayer Pt₂HgSe₃, highlighting optical control of spin- and valley-selective gapless states in a quantum spin Hall material with strong intrinsic spin-orbit coupling.⁹ Together with the new tunnel-barrier proposal, it suggests an emerging subfield: optically programmed jacutingaite spin-valley electronics.

The next experimental milestones are fairly clear. Researchers would need high-quality monolayer or few-layer jacutingaite devices, a way to create a spatially selective off-resonant drive, spin- and valley-sensitive readout, and careful calorimetry or transport diagnostics to separate genuine Floquet filtering from heating artifacts. They would also need to test reversibility: if changing the drive amplitude flips the polarization in theory, the laboratory signature should track that knob cleanly.

What to watch next

Three questions will decide whether the jacutingaite proposal becomes a device roadmap or remains a useful theory exercise. First, can the predicted near-perfect valley filtering survive realistic disorder and contacts? Second, can a confined optical or near-field drive generate the desired photon-dressed mass without excessive heating? Third, can the output polarization be read electrically or optically with enough confidence to prove channel selectivity rather than ordinary barrier tuning?

The broader takeaway is optimistic but disciplined. Floquet engineering is moving from spectacular band-structure ideas toward component-level proposals: barriers, switches, filters, pumps and detectors. Light-gated jacutingaite is one of those component ideas. If it works, it would give quantum-energy researchers a programmable way to sort microscopic carriers by identity—an essential step toward devices where energy, information and topology are controlled together.

Research sources

1. Otman Bouladiane, Kamal Azaidaoui, Clarence Cortes, David Laroze and Ahmed Jellal, “Floquet engineering of spin-valley selective transport in jacutingaite,” arXiv:2608.24533, submitted August 25, 2026. https://arxiv.org/abs/2608.24533
2. Eréndira Santana-Suárez, Brayan E. Walteros-Mendivelso, A. Jazmín Tapia-de-la-Rosa, Mahmoud M. Asmar and David A. Ruiz-Tijerina, “Floquet engineering of topological bands in semiconductor van der Waals heterobilayers,” arXiv:2608.18556, submitted August 19, 2026. https://arxiv.org/abs/2608.18556
3. Muzamil Shah, “Floquet Engineering of Topological Phases and Magneto-Optical Response in a Driven d-wave Altermagnet,” arXiv:2608.11192, submitted August 11, 2026. https://arxiv.org/abs/2608.11192
4. Hou-Jian Duan, Yong-Jia Wu, Xiaoliang Xiao, Ming-Xun Deng, Mou Yang and Rui-Qiang Wang, “RKKY interaction as a probe of valley-dependent spin splitting and odd-parity nature in Floquet collinear magnets,” arXiv:2608.04969. https://arxiv.org/abs/2608.04969
5. Sebastián V. Romero, Xi Chen and Yue Ban, “Bridging continuous control and Floquet driving for charging many-body spin chains,” arXiv:2607.27985, submitted July 30, 2026. https://arxiv.org/abs/2607.27985
6. A. Marrazzo et al., “Signature of large-gap quantum spin Hall state in the layered mineral jacutingaite,” arXiv:1903.02458. https://arxiv.org/abs/1903.02458
7. “Topological transport in monolayer jacutingaite,” arXiv:2412.16965. https://arxiv.org/abs/2412.16965
8. “Edelstein effect in optically driven monolayer jacutingaite Pt2HgSe3,” arXiv:2505.06144. https://arxiv.org/abs/2505.06144