Weyl Semimetals: New States of Matter

Weyl Semimetals: New States of Matter is a thoughtful and accessible exploration of one of the most fascinating frontiers in modern physics and materials science. This book introduces readers to the extraordinary world of Weyl semimetals, a class of quantum materials whose behavior cannot be understood through ordinary ideas of metals, insulators, or semiconductors alone. Instead, these materials reveal a deeper order shaped by topology, symmetry, chirality, and the hidden geometry of electronic bands.The book begins with the broad human search for new states of matter, moving beyond the familiar categories of solid, liquid, gas, and plasma into the modern world of quantum materials. It explains how matter may possess forms of order that are invisible to the eye but powerful in their effects. Through clear and bookish language, it presents the historical importance of Hermann Weyl, whose theoretical ideas about massless chiral fermions later found unexpected life inside solid crystals.At the heart of the book is the concept of the Weyl point, a special crossing in the electronic band structure where electrons behave like massless Weyl quasiparticles. These points carry chirality and topological charge, making Weyl semimetals profoundly different from ordinary materials. The book carefully explains how Weyl points act as sources and sinks of Berry curvature, why they must appear in pairs, and how they give rise to unusual surface states known as Fermi arcs.The work also explores the role of symmetry breaking in creating Weyl states. It shows how the breaking of inversion symmetry or time-reversal symmetry can allow Weyl nodes to appear in real materials. Readers are introduced to nonmagnetic Weyl semimetals, magnetic Weyl semimetals, Type-I and Type-II Weyl semimetals, and the experimental methods used to identify them, including angle-resolved photoemission spectroscopy, scanning tunneling microscopy, magnetotransport, optical spectroscopy, and quantum oscillation studies.Beyond theory and discovery, the book discusses the optical, thermal, and electronic properties of Weyl semimetals. It explains the chiral anomaly, anomalous Hall effect, magnetoresistance, thermoelectric behavior, and possible responses to light and magnetic fields. These properties make Weyl semimetals promising for future technologies such as high-speed electronics, magnetic sensors, photodetectors, spintronics, quantum devices, topological sensors, and advanced optical systems.At the same time, the book gives careful attention to the challenges and limitations of the field. It discusses material imperfections, experimental controversies, Fermi level control, sample quality, surface instability, and the gap between scientific discovery and practical application. This balanced approach makes the book not only inspiring but also realistic.Weyl Semimetals: New States of Matter is a valuable guide for readers interested in quantum materials, condensed matter physics, nanotechnology, advanced electronics, and the future of material discovery. It presents Weyl semimetals as more than scientific curiosities: they are examples of matter becoming geometry, mathematics becoming physical reality, and crystals becoming laboratories for the deepest laws of nature.