Rice and Weizmann Physicists Identify the Electronic Agents Behind Strange Metallicity in a Flat-Band Kagome Metal

Overview

Physicists at Rice University and the Weizmann Institute of Science have identified the fundamental electronic structures responsible for exotic quantum behavior in a class of materials that has long puzzled condensed matter physicists. The team used atomic-resolution spectroscopy to directly visualize what they describe as the governing “agents” of flat-band quantum materials, providing an experimental foundation for theories linking topology, electron correlation, and high-temperature superconductivity. The paper, titled “Origin of strange metallicity in a d-orbital kagome metal,” was published in Nature Physics on March 20, 2026.

What We Know

The research focused on Ni3In, a kagome metal whose geometric lattice structure gives rise to so-called flat bands. In ordinary metals, electrons move relatively freely and carry kinetic energy across the material. In flat-band materials, that motion is suppressed. According to Rice University News, lead theorist Qimiao Si, the Harry C. and Olga K. Wiess Professor of Physics and Astronomy at Rice and director of Rice’s Extreme Quantum Materials Alliance, explained: “In flat band materials, electron motion experiences destructive interference.”

This suppression amplifies the role of electron-electron interactions, pushing the material toward a quantum critical point — a phase transition that occurs at absolute zero temperature and whose fluctuations can be felt at higher temperatures, producing a range of unusual behaviors collectively called strange metallicity. The paper’s title directly addresses this phenomenon: the study aimed to trace strange metallicity in Ni3In back to its microscopic origins.

The experimental work was led by Haim Beidenkopf, a professor at the Weizmann Institute of Science in Israel and the paper’s corresponding author. His team applied atomic-resolution spectroscopic imaging to map the spatial flow of electron currents inside Ni3In. According to BioEngineer.org, the measurements revealed “spatial profiles precisely matching those predicted by the existence of compact molecular orbitals.”

Compact molecular orbitals are tightly localized electronic states that form on a kagome lattice because of its triangular geometry. They are predicted by theory to be the structural building blocks behind flat-band behavior. The Rice–Weizmann study is, according to EurekAlert!, the first experimental confirmation that these orbitals are the active agents governing quantum critical behavior in a real material. Si summarized the result: “This collaboration showed, experimentally, that compact molecular orbitals serve as the agents that underlie the highly agitated quantum critical state of matter.”

Graduate student Mounica Mahankali, a co-first author on the study, described the topological aspect of the finding: “The electronic states are configured such that when one goes through the space of electron states and returns to the starting point, a nonzero winding number has been acquired.” This winding number is a topological invariant — a quantity that cannot change continuously, making it robust against small perturbations of the material. Jean C. Souza is listed as first author on the published study, per Phys.org.

Si offered an analogy to describe how the competing electronic tendencies play out near the quantum critical point. As reported by Phys.org, he compared the system to a highway: “Think of it like a highway with the right lane experiencing stopped, heavy traffic and the left lane experiencing free-flowing, fast-moving traffic.” Electrons in the material dynamically balance between localized states and mobile itinerant states, and the quantum critical point represents the precise balance between the two.

Significance and What Comes Next

Strange metallicity — also called non-Fermi liquid behavior — is one of the central unsolved problems in condensed matter physics. It is observed in a range of strongly correlated materials, including high-temperature copper-oxide superconductors, and its microscopic origin has been debated for decades. By identifying compact molecular orbitals as the governing electronic agents in a specific kagome metal, the Rice–Weizmann collaboration provides a concrete, experimentally testable mechanism that may extend to other material families.

The EurekAlert! press release notes that the findings could inform the search for new quantum applications and advance the understanding of high-temperature superconductivity. Flat-band materials are also topological, meaning their characteristic electronic properties are preserved against continuous deformations of the lattice that respect the crystal’s symmetry — a robustness that makes them attractive candidates for quantum devices.

What We Don’t Know

Whether compact molecular orbitals serve as the governing agents in other kagome metals, or in flat-band materials with different lattice geometries, remains an open question. Ni3In is a d-orbital kagome metal, and the researchers chose it precisely because its properties were expected to reflect flat-band physics in a tractable form. Extending the result to other material classes — including the copper-oxide superconductors whose strange metallicity has been studied longest — will require further experimental and theoretical work.

The study also does not directly observe or engineer superconductivity in Ni3In; the connection to high-temperature superconductivity is inferential, grounded in the shared phenomenology of strange metallicity and quantum criticality. Whether the experimental handle on compact molecular orbitals demonstrated here can be used to design materials that are superconducting at higher temperatures is a question the field will now pursue.