Indian Scientists Decode Topological Secrets of Quantum Materials Using Spectral Function

In a groundbreaking advancement in the field of condensed matter physics, researchers from the Raman Research Institute (RRI) in Bengaluru have discovered a novel method to detect a fundamental property of quantum materials—topological invariants—by analyzing a quantum characteristic known as the spectral function. This innovation promises to significantly streamline the study and classification of topological materials, which form the backbone of future technologies including quantum computing, fault-tolerant electronics, and energy-efficient systems.

The pioneering research was led by Professor Dibyendu Roy and PhD scholar Kiran Babasaheb Estake, and has been recently published in the reputed journal Physical Review B. Their findings challenge long-standing assumptions in experimental physics, offering a fresh perspective on how topology—traditionally understood in abstract mathematical terms—can be directly probed through physical properties accessible in laboratory settings.

Understanding Topology in Quantum Materials

At the heart of this discovery lies the concept of topological invariance, a property that remains unchanged even when an object undergoes continuous deformations such as stretching or bending, provided there is no tearing or gluing involved. A classic analogy from topology compares a donut (or wada) and a coffee mug—both of which are topologically equivalent because they have one hole. An idli, having no holes, is topologically different from a donut. These differences, though abstract in appearance, are fundamental in characterizing the quantum geometry of materials.

In advanced materials such as topological insulators and superconductors, electrons do not behave uniformly. Instead, their movement and properties depend on underlying quantum shapes, not visible to the naked eye but described mathematically by quantities like winding numbers in one-dimensional (1D) systems and Chern numbers in two-dimensional (2D) systems. These are the topological invariants—hidden numerical codes that govern particle behavior within the quantum realm.

A New Window into the Quantum World

Until now, scientists primarily relied on techniques such as Angle-Resolved Photoemission Spectroscopy (ARPES) to study these materials. ARPES allows physicists to map the momentum and energy of electrons, thereby offering insight into the material's electronic structure. However, ARPES and similar techniques have limitations when it comes to directly observing topological invariants.

This is where the new research brings a revolutionary shift. The spectral function, a long-standing tool used to determine properties like the density of states and dispersion relations in materials, has now been shown to contain signatures of topology. By analyzing the momentum-space spectral function (SPSF), the RRI team has revealed that it is possible to extract topological information—effectively enabling scientists to “see” the topology without resorting to traditional, often complex, observational techniques.

Implications and Potential Applications

“This is a significant shift in our understanding,” said Kiran Babasaheb Estake, lead author of the study. “The spectral function has always been used to probe fundamental electronic properties. Our research shows that it can also reveal topological characteristics, which opens a new paradigm in condensed matter research.”

The ramifications of this work are vast. By using the spectral function as a universal diagnostic tool, scientists may now classify a wide array of quantum materials with greater accuracy and efficiency. This is particularly crucial for the development of next-generation quantum technologies, where topological stability ensures fault tolerance, a core requirement for quantum computers.

Furthermore, the discovery can aid in the design of energy-efficient electronic systems, as topological materials often exhibit dissipationless edge currents—a property that can drastically reduce energy losses in circuits and sensors.

A Leap for Indian Science and Global Condensed Matter Research

The work coming out of the Raman Research Institute, an autonomous institute under India’s Department of Science and Technology, demonstrates the country’s growing impact on fundamental physics research. It also aligns with India’s broader vision of becoming a global leader in quantum science and emerging technologies.

As Professor Dibyendu Roy explained, “This approach may become a standard framework for experimentalists in the future. The ability to detect topological invariants through the spectral function simplifies the process and opens the door to identifying new materials with exotic quantum properties.”

With this breakthrough, Indian scientists have not only expanded the theoretical understanding of quantum materials but also provided a powerful experimental pathway that could accelerate innovation in one of the most exciting frontiers of modern science.