Fusion reactors present a particularly harsh setting: the first wall—shielding the fuel—degrades under intense radiation. Engineers currently monitor damage indirectly because silicon-based sensors cannot survive long enough inside the barrier, often requiring costly shutdowns for inspection.

After irradiation, the GNR devices still responded electrically, even though their performance changed dramatically. That combination—survival plus a clear, measurable output shift—is exactly what a radiation sensor must deliver to enable more reliable, condition-based maintenance planning.

The study connects the electrical response to atomic-scale effects. Measurements suggest that gamma exposure leaves the nanoribbon’s overall framework intact while altering the ribbon edges through radiation-driven reactive molecules in the surrounding air. Because transport in such narrow structures is governed by quantum rules, even subtle edge modifications can produce outsized changes in current flow.

The researchers propose that the signal arises from Anderson localization, a quantum phenomenon in which electrons become trapped by disorder. In this scenario, irradiation-induced changes reduce charge transport sharply, turning the nanoribbon into a sensitive indicator of radiation exposure.

Beyond fusion, the implications extend to space systems. Satellites, Earth-observation missions, and deep-space probes all face long-duration radiation environments where early detection of radiation-related wear could prevent failures before they occur.

To achieve the required precision, the team synthesized GNRs from the molecular level and embedded them in standard semiconductor device platforms. The ribbons were fabricated to be about one atom thick and roughly 45 nanometers long, producing a structure thin enough for quantum effects to dominate behavior.

Future work will test a range of gamma doses and fabricate GNRs of different sizes. The researchers also emphasize that the fabrication approach is designed to allow atom-by-atom tailoring of sensitivity, enabling radiation systems that can be engineered to respond—or not respond—within specific regimes.

Keywords

Graphene nanoribbons, gamma radiation, semiconductor devices, quantum transport, Anderson localization, radiation sensing, fusion energy, space electronics

Subject of Research: Graphene nanoribbons as radiation-sensing elements
Article Title: Electrical and Structural Response of Nine-Atom-Wide Armchair Graphene Nanoribbon Transistors to Gamma Irradiation
News Publication Date: 20-Apr-2026
Web References: http://dx.doi.org/10.1021/acsami.6c02516
References: 10.1021/acsami.6c02516
Image Credits: Photo by Leslie Hawthorne Klingler, University of Arizona Office of Research and Partnerships

At the heart of modern nanoelectronics lies the persistent challenge of overcoming scaling limitations that traditional transistor architectures face as dimensions shrink toward atomic scales. The gate-all-around transistor, particularly those leveraging nanosheet geometries, represents a paradigm shift from conventional FinFET structures by providing superior electrostatic control. However, as the conduction channels narrow significantly, quantum mechanical effects such as tunneling and electron confinement become dominant, profoundly affecting device performance. The researchers’ focus on how quantum transport evolves when electrons negotiate a constriction inside nanosheet GAA transistors is therefore of immense significance both academically and technologically.

The team employed a combination of sophisticated modeling techniques and experimental validation to explore the nature of electron flow under these nanoscale constrictions. Their approach marries the application of quantum transport theory—grounded in non-equilibrium Green’s function formalism—with state-of-the-art fabrication methods to realize nanosheet devices featuring precisely engineered constrictions. These minute structural bottlenecks mimic realistic operational conditions where current must pass through regions smaller than the electron wavelength, invoking phenomena rarely encountered in classical semiconductor electronics. Such meticulous integration of theory and practice enables the researchers to capture nuanced subtleties governing electron dynamics at nanometric scales.

One of the standout revelations of the study was the identification of unique resonant tunneling effects occurring within the nanosheet constriction. As electrons approach the narrowed channel, their wave functions undergo complex interference patterns that either enhance or suppress transmission probabilities depending on energy and geometric parameters. These resonances are highly sensitive to the atomic-scale configuration of the constriction, and by tweaking its dimensions, the team demonstrated the capacity to modulate current flow with unprecedented precision. This fine control over quantum transport mechanisms paves the way for novel transistor functionalities leveraging quantum coherence and interference, aspects traditionally overlooked in classical device engineering.

Furthermore, the research highlights the impact of electron-phonon interactions in this confined geometry, revealing that lattice vibrations play a non-trivial role in damping quantum coherence across the constriction. Through detailed theoretical treatment and corroborating experiments, the study elucidates how these inelastic scattering processes influence device behavior, adding layers of complexity to electron transport not accounted for by simpler ballistic models. Understanding these interactions is critical for optimizing transistor performance, particularly concerning power dissipation and thermal stability, which directly affect the reliability of nanoscale devices under real-world operating conditions.

From a materials science perspective, the investigation underscores the importance of atomic-level control and material quality in defining quantum transport characteristics. Variations in material composition, interface roughness, and defect densities emerge as potential barriers or facilitators of electron passage through the constricted nanosheet channels. The findings advocate for refined fabrication techniques capable of achieving angstrom-level uniformity to minimize variability and bolster coherence effects that enhance device functionality. This emphasis on material precision aligns with broader trends in semiconductor manufacturing, where atomic-scale engineering is rapidly becoming a prerequisite for next-generation device architectures.

Another dimension of the study delves into the energetics governing electron distribution inside the constricted nanosheets. By mapping out the band structure alterations induced by geometrical confinement and electrostatic gating, the researchers provide a comprehensive picture of how energy barriers and quantum wells emerge within these minuscule components. These electronic landscapes are pivotal in determining charge carrier mobility and switching speeds, key metrics for transistor efficiency. The team’s insights into tuning band alignments through gate voltages and structural parameters reveal practical pathways to optimize device response dynamically in operational circuits.

Importantly, the implications of this work extend beyond traditional digital logic applications. The precise modulation of quantum transport through nanosheet constrictions heralds promising opportunities for quantum information processing, sensor technologies, and novel analog computing paradigms. Devices exploiting controllable quantum interference could form the basis of ultra-sensitive detectors, low-noise amplifiers, or components in quantum computing circuits where coherence preservation is paramount. The multidisciplinary character of this research bridges condensed matter physics, electrical engineering, and nanotechnology, fostering innovations across several emerging fields.

Technological scalability figures prominently in the discussion, as the authors address the challenges of integrating these constricted nanosheet transistors into large-scale semiconductor manufacturing processes. While laboratory-scale demonstrations showcase remarkable control over quantum phenomena, translating these advances into mass production requires addressing yield, reproducibility, and compatibility with existing complementary metal-oxide-semiconductor (CMOS) platforms. Nonetheless, the demonstrated theoretical and experimental frameworks establish a roadmap for future innovation, encouraging industrial stakeholders to invest in fabrication technologies that embrace quantum-mechanical device concepts.

The study also revisits classical transport assumptions, contrasting ballistic, diffusive, and localized regimes observed in nanosheet devices under varying constriction geometries and temperatures. This comprehensive analysis frames a richer understanding of electron dynamics, guiding device engineers in selecting design parameters tailored to specific performance goals. By articulating this nuanced perspective on transport regimes, the research contributes a vital knowledge base essential for confronting the ever-shrinking scales of semiconductor devices without sacrificing operational integrity.

In addition, the authors explore the role of electrostatic gating in modulating the constriction potential landscape, demonstrating the dynamic tunability of electron transmission pathways. By applying gate voltages, the effective width and height of the conduction channel can be modified in situ, allowing real-time control over quantum transport properties. This ability to electrically steer quantum behavior introduces a new dimension to transistor functionality, potentially enabling adaptive circuits that respond intelligently to environmental or computational demands.

Moreover, the research touches upon the challenges posed by variability and noise stemming from quantum fluctuations and atomic-scale disorder within the nanosheet constrictions. Recognizing these sources of device instability is critical for developing mitigation strategies such as error correction, redundancy, or design optimizations to ensure robust performance in practical applications. The authors’ quantitative treatment of fluctuation effects paves the way for future inquiries into device reliability and error tolerance in quantum-dominated regimes.

Intriguingly, the investigation also hints at potential compatibility with emerging two-dimensional materials, suggesting that nanosheet gate-all-around transistors may one day incorporate novel semiconductors like transition metal dichalcogenides or graphene derivatives. Such materials promise even greater control over electron confinement and transport, potentially amplifying the quantum effects observed. By contextualizing their findings within a broader materials landscape, the researchers invite exploration into hybrid devices merging traditional silicon technology with next-generation semiconductors.

The implications for power efficiency cannot be overstated. As conventional transistor scaling encounters diminishing returns due to leakage currents and short-channel effects, the ability to harness quantum transport through nanosheet constrictions offers pathways to significantly reduce power consumption. By enabling sharper switching behaviors and suppressing undesired conduction channels through quantum interference, these devices could revolutionize low-power electronics, extending battery lives and decreasing the environmental footprint of computational infrastructure.

Finally, the study serves as an inspiring blueprint for harnessing quantum mechanics in practical electronic devices, revitalizing interdisciplinary collaboration between physicists, engineers, and material scientists. The elegant conjunction of theoretical rigor, experimental finesse, and technological foresight embodied by Kim, Park, Jin, and their colleagues’ work represents a pivotal stride toward the quantum era of semiconductor electronics, where classical limitations give way to unprecedented control over electronic behavior at the smallest scales.

Subject of Research: Quantum transport phenomena in nanosheet gate-all-around transistors featuring nanoscale constrictions.

Article Title: Quantum transport through a constriction in nanosheet gate-all-around transistors

Article References:
Kim, K.Y., Park, HH., Jin, S. et al. Quantum transport through a constriction in nanosheet gate-all-around transistors. Commun Eng 4, 92 (2025). https://doi.org/10.1038/s44172-025-00435-0

Image Credits: AI Generated

Coulomb drag is an inherently fascinating phenomenon where the movement of charged particles, or current, in one conductor can induce a voltage in a nearby but electrically isolated conductor. This interaction arises purely through long-range Coulomb forces — the electrostatic repulsion or attraction between charged particles — without any direct electrical contact. Previous studies have characterized Coulomb drag extensively in conventional two-dimensional electron systems, but exploring this effect in topological materials marked by non-trivial band structures has remained an elusive challenge until now.

Chern insulators represent a unique class of magnetic topological materials distinguished by their capacity to exhibit the quantum anomalous Hall effect (QAH). Unlike the classic quantum Hall effect, which necessitates external magnetic fields, Chern insulators display quantized Hall conductance due to intrinsic magnetization combined with robust chiral edge states that allow dissipationless transport along their boundaries. These edge modes are resilient to disorder and scattering, making Chern insulators prime candidates for applications in spintronics and quantum information.

The significance of this research lies not only in the pioneering observation of a non-reciprocal Coulomb drag effect but also in its implications for the control and detection of quantum states in advanced materials. Non-reciprocal phenomena, where the physical response depends on the direction of applied stimuli, are of increasing interest because they can enable new electronic functionalities, such as rectification and isolation, fundamental to quantum circuits and devices. By demonstrating such asymmetry in Coulomb drag, the research reveals intricate coupling mechanisms between quantum edge states mediated by Coulomb interactions.

To execute these experiments, the team employed molecular beam epitaxy (MBE) to grow ultrathin films of vanadium-doped (Bi,Sb)₂Te₃, a prototypical topological insulator system chemically engineered to promote a high-temperature quantum anomalous Hall effect. Utilizing a dual Hall-bar device architecture separated by a nanoscale vacuum gap ensured that coupling between layers occurred exclusively through Coulomb forces, eliminating unwanted tunneling currents that could mask the pure electrostatic interaction signals. This meticulous device design allowed precise probing of Coulomb drag dynamics under stringent experimental conditions.

Measurements were conducted at ultra-low temperatures reaching as low as 20 millikelvin and under perpendicularly applied magnetic fields to investigate the detailed interplay of magnetization and quantum transport phenomena. The researchers recorded both longitudinal (along current direction) and transverse (perpendicular to current flow) drag voltages, supplementing these with current-voltage (I-V) characterizations to differentiate between shot noise and mesoscopic fluctuation regimes. Temperature-dependent scaling analysis further confirmed the mesoscopic origins of the observed behaviors.

One of the most striking findings was the fixed polarity of longitudinal drag signals regardless of the current direction or magnetic field polarity. This rectification-like property indicates an inherent directionality in Coulomb drag, breaking conventional expectations of reciprocal behavior in electronic transport. Conversely, the transverse drag exhibited a clear dependence on the magnetization’s orientation, pinpointing the role of chiral edge state couplings between the layers as the dominant conduit for non-reciprocal interactions.

Delving into the underlying mechanisms, the study identified mesoscopic fluctuations as the primary factor influencing Coulomb drag at ultra-low temperatures, with a characteristic quadratic temperature dependence (T²). As bias currents increased, shot noise—quantum noise intrinsic to discrete charge carriers—became the prevailing driver, introducing nonlinearities in the drag voltages that correspond to changes in quantum transport regimes. This duality underscores the rich complexity of electron correlations in topological insulator systems and opens avenues for tuning device responses by controlling temperature and bias conditions.

Beyond fundamental physics, these insights have profound implications for the rapidly advancing field of topological quantum computing. The non-contact detection technique introduced here provides a sensitive probe for quantum states, particularly those relevant to qubit operations based on Majorana fermions and other exotic quasiparticles. The ability to monitor quantum coherence and state transitions without perturbing fragile quantum information is a critical milestone toward scalable and robust quantum technologies.

Moreover, the asymmetric Coulomb drag effect uncovered in Chern insulators could inspire innovative device architectures that leverage magnetization dynamics to enable low-power, chiral electronic components. Devices exploiting such directional coupling could revolutionize spintronic circuits, offering new pathways to integrate magnetic control with topological robustness for improved performance and energy efficiency.

This breakthrough underscores the power of combining cutting-edge materials science with precision quantum transport measurements to unlock unforeseen physical phenomena. By charting previously unexplored territory in non-reciprocal Coulomb drag, He Qinglin’s group has expanded our comprehension of topology-driven quantum interactions and set the stage for future explorations that may transform quantum electronics and computation.

The publication of this work in Nature Communications attests to its significance within the physics community and its potential impact across multiple domains including condensed matter physics, quantum materials engineering, and information science. As researchers worldwide build on these findings, this report will stand as a seminal contribution highlighting the interplay of topology, magnetism, and Coulomb interactions in quantum materials.

Pioneering experimental techniques, such as the dual Hall bar nanoscale gap device employed by the team, illustrate the meticulous engineering necessary to study subtle quantum effects. This approach could be adapted to investigate other topological phases or explore dynamic control of quantum states via external stimuli. The synergy between intrinsic material properties and novel measurement strategies signals a vibrant future for the field.

In sum, the first observation of non-reciprocal Coulomb drag in magnetic Chern insulators marks a milestone that bridges fundamental quantum physics and emerging quantum technology. This achievement expands the horizon for identifying and harnessing new quantum phenomena where topology, symmetry breaking, and electron correlations converge, paving the way for breakthroughs in understanding and utilizing complex quantum systems.

Subject of Research: Observation and analysis of non-reciprocal Coulomb drag phenomena in magnetic Chern insulators exhibiting quantum anomalous Hall effects.

Article Title: Non-reciprocal Coulomb drag between Chern insulators

News Publication Date: April 24, 2025

Web References:

• Nature Communications article DOI: 10.1038/s41467-025-58401-5
• Full article (PDF)

Keywords

Topology, Quantum states, Quantum anomalous Hall effect, Chern insulators, Coulomb drag, Quantum materials, Mesoscopic fluctuations, Shot noise, Non-reciprocal transport, Majorana qubits, Molecular Beam Epitaxy, Quantum computing