An example of condensed matter physics that is widely understood by most people is the phenomenon of phase transitions, such as the transition from a liquid to a solid state (freezing) or from a liquid to a gas state (boiling). While these transitions are familiar in everyday life, they are also subjects of intense study in condensed matter physics.
Phase transitions involve changes in the collective behavior of large numbers of atoms or molecules. The transition occurs when certain conditions, such as temperature or pressure, cross a critical threshold, leading to a dramatic change in the physical properties of the material.
For instance, when a substance is cooled below its freezing point, the individual particles become more ordered, and they arrange themselves into a regular lattice structure, forming a solid. Conversely, when the substance is heated above its boiling point, the particles gain enough energy to overcome intermolecular forces, and the substance transitions into a gas, where the particles are much more disordered and widely separated.
Phase transitions are not limited to simple freezing or boiling processes but can occur in a variety of systems. For example, ferromagnetism is another well-known phenomenon in condensed matter physics. In certain materials, such as iron or cobalt, the individual magnetic moments of the atoms align parallel to each other, resulting in a net magnetic field. When these materials are heated above a critical temperature known as the Curie temperature, the alignment breaks down, and they lose their magnetism.
Superconductivity, as you mentioned, is another intriguing example. It refers to the phenomenon where certain materials exhibit zero electrical resistance when cooled below a critical temperature. This discovery has led to technological advancements such as high-speed trains (maglev) and highly sensitive magnetic field detectors (SQUIDs).
These examples highlight how condensed matter physics studies the behavior of matter in bulk and how it undergoes fascinating transitions that impact our daily lives.