Physicists Detect Elusive Hall Effect Phenomenon for the First Time

In a groundbreaking advancement that challenges longstanding conventions in condensed matter physics, researchers from Japan have reported the first-ever observation of a giant anomalous Hall effect (AHE) in a nonmagnetic material. This extraordinary phenomenon was uncovered using high-quality thin films of Cd₃As₂, a Dirac semimetal, subjected to an in-plane magnetic field. By tactically manipulating the material’s electronic band structure, the research team succeeded in isolating the AHE, demonstrating that its origin lies in orbital magnetization rather than the electron spin—a revelation that overturns decades of theoretical assumptions.

The Hall effect, first discovered in 1879 by Edwin Hall, arises when an electric current passing through a conductor in a magnetic field experiences a transverse voltage due to the Lorentz force acting on moving charges. This fundamental phenomenon rapidly became a cornerstone in electromagnetism and solid-state physics, leading to various applied technologies and the discovery of novel quantum effects. Shortly after the initial identification of the classical Hall effect, physicists observed a similar but more enigmatic effect in ferromagnetic materials, which was designated the anomalous Hall effect. Unlike the classical Hall effect, where magnetic fields directly influence charge carriers, the AHE is intricately tied to the intrinsic magnetic properties of the material.

Despite being a subject of intense theoretical and experimental scrutiny for nearly a century, the exact origins of the anomalous Hall effect have remained elusive. Traditional understanding holds that the AHE stems primarily from spin-dependent scattering mechanisms and intrinsic spin-orbit coupling in ferromagnetic substances. However, sophisticated theoretical frameworks developed over the past few decades hinted that AHE-like behavior might also emerge in nonmagnetic materials under specific conditions. Such predictions, although tantalizing, lacked empirical verification until now.

The recent study, led by Associate Professor Masaki Uchida from the Institute of Science Tokyo, constitutes a significant leap forward by providing the first experimental evidence of AHE manifesting robustly in a nonmagnetic system. The results were published in the prestigious journal Physical Review Letters on September 2, 2025, marking a milestone in our understanding of electron transport phenomena in topological materials. This research not only validates prior theoretical predictions but also unlocks new avenues for electronic device engineering.

Central to the experiment is the choice of Cd₃As₂, a prototypical Dirac semimetal characterized by linear band crossings called Dirac points, where electrons mimic relativistic, massless particles. These materials harbor unique electronic topologies, making them fertile ground for observing exotic quantum phenomena. When subjected to an external perturbation, such as a magnetic field applied within the plane of the thin film, the inherent crystalline symmetries are broken, and the Dirac points split into pairs of Weyl nodes. This splitting fundamentally alters the Berry curvature distribution and electron dynamics, fostering conditions conducive to an anomalous Hall current.

Through meticulous band structure engineering, Uchida’s team adeptly suppressed contributions from the classical Hall effect, enabling the exclusive probing of the anomalous Hall conductivity. This delicate disentanglement relied on molecular beam epitaxy to fabricate atomically smooth Cd₃As₂ films with pristine symmetry properties. By finely tuning the magnetic field orientation and measuring the transverse voltage response, the team quantified the magnitude of the induced AHE with unprecedented precision, revealing a surprisingly large Hall angle comparable to ferromagnetic materials.

Crucially, further analysis of the experimental data illuminated that the dominant mechanism behind the observed AHE is not spin magnetization, as conventionally believed, but orbital magnetization—the magnetic moment arising from the cyclotron motion of electrons around the lattice sites. This insight introduces a paradigm shift in interpreting Hall effects, expanding the scope of orbital degrees of freedom in electronic transport. It underscores the role of Berry phase effects linked to the orbital motion of electrons, underscoring the richness of quantum geometrical contributions beyond spin physics.

The broader implications of this study are profound. By demonstrating that a giant anomalous Hall effect can exist in nonmagnetic materials, the findings greatly expand the landscape of materials suitable for spintronic and quantum electronic applications. Devices that exploit AHE to manipulate charge and magnetization could now be engineered without relying on ferromagnetic components, potentially enhancing energy efficiency, operational frequency, and stability under diverse conditions. This breakthrough sets the stage for innovative sensor technologies, memory storage, and information processing units that leverage orbital-controlled phenomena.

Moreover, the experimental approach pioneered by Uchida’s group—combining precision thin-film growth with directional magnetic field application and transport measurements—provides a versatile platform to probe subtle electron correlations and topological states in a variety of materials. The universal applicability of this methodology paves the way for exploring uncharted territories, such as novel topological phases and emergent quantum states governed by orbital magnetism, which have remained experimentally inaccessible until now.

The discovery also invites renewed theoretical investigations aimed at comprehensively modeling the interplay between orbital magnetization, Berry curvature, and electronic band structure under symmetry-breaking perturbations. It challenges conventional spin-based narratives in magnetotransport and compels physicists to revisit foundational models of the Hall effect with an expanded conceptual toolkit. This evolving understanding may influence future quantum material design, prioritizing orbital characteristics as key tunable parameters.

In conclusion, this study not only answers a long-standing question in condensed matter physics but also serves as a catalyst for interdisciplinary advances at the nexus of materials science, electronics, and quantum physics. As Associate Professor Uchida remarks, the demonstration of AHE in nonmagnetic Dirac semimetals reshapes our understanding and promises technological innovations that harness the orbital dynamics of electrons. With further research and development, this phenomenon could usher in a new generation of electronic devices exhibiting remarkable functionalities.

The Institute of Science Tokyo, formed in 2024 through the pioneering merger of Tokyo Medical and Dental University with Tokyo Institute of Technology, represents a vibrant hub for cutting-edge scientific research and technological innovation. This discovery distinctly exemplifies their mission of advancing human wellbeing through transformative science. Supported by notable organizations including the Japan Science and Technology Agency and the Ministry of Education, Culture, Sports, Science and Technology, the team’s achievements spotlight Japan’s prominent role in next-generation condensed matter physics.

As the implications of this research reverberate through the physics community and beyond, the anomalous Hall effect in nonmagnetic Dirac semimetals heralds a new chapter characterized by exciting possibilities and fundamental insights into the quantum properties of matter.

Subject of Research:

Article Title: Anomalous Hall effect in the Dirac semimetal Cd3As2 probed by in-plane magnetic field

News Publication Date: 2-Sep-2025

Web References:

https://journals.aps.org/prl/accepted/10.1103/5d7l-mr7k

References:

Physical Review Letters, “Anomalous Hall effect in the Dirac semimetal Cd3As2 probed by in-plane magnetic field,” 2025. DOI: 10.1103/5d7l-mr7k

Image Credits: Institute of Science Tokyo

Keywords

Physical sciences, Applied sciences and engineering, Electrical engineering, Electronics, Electronic devices

Tags: advances in solid-state physicscondensed matter physics breakthroughsDirac semimetalselectric current and Lorentz forcegiant anomalous Hall effecthigh-quality thin filmsmagnetic field influence on conductorsnonmagnetic materialsnovel material propertiesorbital magnetization in physicsquantum effects in electromagnetismtheoretical assumptions in physics