Quantum physics and solid-state physics are closely related fields, but they focus on different aspects of physics.
Quantum physics, also known as quantum mechanics, is a fundamental theory that describes the behavior of matter and energy at the smallest scales. It provides a mathematical framework to understand the nature of particles, waves, and their interactions. Quantum physics deals with phenomena such as wave-particle duality, superposition, entanglement, and quantization of energy levels.
Solid-state physics, on the other hand, is a subfield of condensed matter physics that specifically studies the properties and behavior of solid materials. It examines how the arrangement and interaction of atoms in a solid give rise to various physical phenomena. Solid-state physics investigates the electrical, magnetic, thermal, optical, and mechanical properties of materials at the macroscopic scale, while taking into account the underlying quantum mechanical principles.
In essence, solid-state physics builds upon the principles of quantum mechanics to study the behavior of materials and systems composed of a large number of interacting particles. It focuses on topics such as crystal structure, lattice vibrations, electronic band structure, semiconductors, magnetism, superconductivity, and optical properties of solids.
While quantum physics provides the theoretical foundation for understanding the microscopic behavior of matter and energy, solid-state physics applies this understanding to real-world materials and systems, with a particular emphasis on solids.