Condensed matter physics

Condensed matter physics is a part of science that studies how tiny parts like atoms and electrons work together to make bigger things, such as solids and liquids. Scientists in this field look at special ways materials can behave.

This area of science is very important today. It helps us understand and create new materials that are used in many technologies. Condensed matter physics connects with other subjects like chemistry, materials science, and even nanotechnology.

The study of how materials behave has grown from older ideas about metals and crystals. Important work in this area started a long time ago, with scientists like Albert Einstein helping to shape what we know today.

Etymology

The term "condensed matter" was made by physicists Philip Warren Anderson and Volker Heine in 1967. They changed their group's name at the Cavendish Laboratories in Cambridge from "Solid state theory" to "Theory of Condensed Matter." They wanted to include liquids and other materials too.

Before this, some physicists in Europe had already used the term. This was especially true in a journal called Physics of Condensed Matter that started in 1963.

The name "condensed matter physics" was chosen because it covers many types of materials, like solids and liquids. The older name "solid state physics" focused mostly on metals and semiconductors.

Some physicists thought the new name fit better with how research was funded and the political climate of the Cold War time.

Even earlier, in 1947, a scientist named Yakov Frenkel suggested calling liquids and solids "condensed bodies" because they have similar behaviors.

History

Further information: Timeline of condensed matter physics

Classical physics

One of the first studies of solid and liquid materials was done by an English chemist named Humphry Davy in the early 1800s. He noticed that many elements had qualities like shine, flexibility, and good electrical and heat conduction. This showed that atoms had more structure than previously thought. Davy also thought that gases like nitrogen and hydrogen could be turned into liquids and act more like metals.

In 1823, Michael Faraday successfully turned chlorine into a liquid and later did the same with all known gases except nitrogen, hydrogen, and oxygen. In 1869, Thomas Andrews studied how liquids turn into gases and created the idea of a critical point. Johannes van der Waals provided a theory to explain this behavior. By 1908, James Dewar and Heike Kamerlingh Onnes were able to turn hydrogen and helium into liquids.

Paul Drude created the first model in 1900 to explain how electrons move in metals. However, it couldn’t fully explain some metal properties. In 1911, Heike Kamerlingh Onnes discovered superconductivity in mercury, where it lost all electrical resistance at very low temperatures. This surprised scientists.

Advent of quantum mechanics

Drude’s model was improved by several scientists using quantum mechanics. Pauli used new ideas about electrons to explain certain magnetic properties. Sommerfeld improved the model further, and Bloch used quantum mechanics to describe electrons in crystals.

Scientists developed ways to classify crystals by their patterns. In 1947, John Bardeen, Walter Brattain, and William Shockley created the first transistor, starting a revolution in electronics.

In 1879, Edwin Hall discovered that running electricity through a material in a magnetic field creates a voltage across the material. This became known as the Hall effect. Later, Lev Landau developed theories that helped explain related effects.

People have known about magnetism for thousands of years, but modern studies began in the 1800s. Scientists learned to classify materials based on how they respond to magnetic fields. They discovered important ideas about how tiny parts of materials work together to create magnetism.

Modern many-body physics

After World War II, new ideas from quantum theory were used to study materials. Scientists learned about how particles work together in solids and introduced the idea of quasiparticles. Lev Landau developed theories to explain the behavior of certain particles and phase changes in materials. In 1956, John Bardeen, Leon Cooper, and Robert Schrieffer created a theory to explain superconductivity.

In the 1960s, scientists studied how materials change at critical points. In 1980, Klaus von Klitzing discovered the quantum Hall effect, where certain measurements stayed exactly the same no matter the size of the material. This led to new ideas about the structure of materials. In 1986, Karl Müller and Johannes Bednorz discovered materials that could become superconducting at much higher temperatures than before.

In 2012, research suggested that samarium hexaboride might have special properties that allow it to act as a topological insulator.

Theoretical

Main article: Emergence

Theoretical condensed matter physics uses simple ideas to help us learn how different states of matter act. These ideas look at things like how tiny parts called electrons move in solids and how materials change from one state to another, such as from a regular solid to a superconductor.

Understanding condensed matter physics often talks about emergence. This means that when many tiny parts come together, they can act in new ways that single parts don’t. For example, some materials can carry electricity with no loss at very cold temperatures, even though we know a lot about the small parts that make up the material.

Electronic theory of solids

Main article: Electronic band structure

Metals have been important for studying solid materials. One of the first ways scientists described metals was by thinking of them as a gas made of tiny parts called electrons. This helped explain why metals carry electricity and heat.

Later, scientists learned that metals have a regular pattern of atoms, which changes how electrons move through them. Today, we use computers and math to guess how electrons act in complicated materials, which helps us learn about and make new kinds of matter with special traits.

Symmetry breaking

Main article: Symmetry breaking

Some materials change how they act in special ways. For example, solid crystals have a repeating pattern, and magnets can point in one direction. These changes happen because the material’s overall balance is “broken” in a certain way.

When balance breaks, it can make new tiny vibrations or movements in the material. These are like waves that travel through the material and help scientists learn about its traits.

Phase transition

Main article: Phase transition

A phase transition is when a material changes from one state to another, like when ice turns into water. This usually happens when we change something about the material, such as its temperature or pressure.

Sometimes, even at the coldest possible temperature, materials can change how they act because of tiny parts called quantum effects. These changes help explain why some materials act in very unusual ways, such as carrying electricity perfectly with no loss. Learning about these changes helps scientists understand and guess how many different materials will act.

Experimental

Experimental condensed matter physics uses special tools to learn new things about materials. Scientists use electric and magnetic fields to see how materials react. They also measure how materials move heat and electricity, and they study materials using light and other types of energy.

One common way to study materials is by using scattering, where scientists shine things like X-rays or visible light on the material to see how it changes. Neutrons can also be used to look at tiny parts of materials.

Ultracold atom trapping in optical lattices is a special tool used to study materials. Scientists use lasers to create patterns that trap very cold atoms. These cold atoms can act like models for more complex materials, helping scientists understand how some materials behave. In 1995, scientists made a special kind of material called a Bose–Einstein condensate by cooling rubidium atoms to a very low temperature.

Scattering

Further information: Scattering

Scientists often study materials by scattering different types of energy, like X-rays, visible light, or neutrons, off the material. The type of energy they use depends on what they want to see. Visible light can show changes in how the material looks, while X-rays can show the tiny building blocks of the material. Neutrons can also be used to look at tiny parts of materials, especially how tiny pieces called spins are arranged. Electron beams can be used to study how electrons move, and laser spectroscopy helps scientists see very small details of materials.

External magnetic fields

In experiments, magnetic fields are used to change how materials behave. By using strong magnetic fields, scientists can learn about the tiny parts inside materials, like how atoms are arranged. One method called nuclear magnetic resonance (NMR) uses magnetic fields to study the structure of materials. Stronger magnetic fields give better information.

Magnetic resonance spectroscopy

Scientists use special methods like electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) to study the tiny parts of materials. These methods are very good at showing how atoms and tiny pieces called spins are arranged around them. They help scientists learn about changes in materials and how tiny parts move.

Cold atomic gases

Main article: Optical lattice

Trapping very cold atoms using lasers is a common tool in studying materials. Lasers create patterns that act like a grid, holding atoms in place at very low temperatures. These cold atoms can act like models for more complicated materials, helping scientists understand how some materials behave. In 1995, scientists made a special state of matter called a Bose–Einstein condensate by cooling rubidium atoms to an extremely low temperature.

Applications

Research in condensed matter physics has led to many useful inventions, like semiconductor transistor technology, laser tools, magnetic storage devices, liquid crystals, and optical fibres. These discoveries also help us study very tiny things, thanks to tools like scanning-tunneling microscopy.

This field of science also helps in building new computers using quantum computation methods. And it even helps doctors see inside the body better with magnetic resonance imaging.