High Pressure Physics
The PIs working in this area:
Xiaojia Chen, Bin Chen, Zhiqiang Chen, Wenge Yang, Lin Wang.
The primary effect of high pressure is volume contraction and hence the shortening of interatomic and intermolecular distances. Along with structural modifications are various changes in physical properties such as electric/thermal conductivity, viscosity, melting and magnetic properties. Exploring and understanding the new physical phenomenon under high pressure will open new avenues for designing and synthesizing materials with unique properties. The development of new intense X-ray and neutron sources leads to a revolution in high-pressure science.
At HPSTAR, the research of high pressure physics include (but not limited to) the following aspects:
New Crystallography - Symmetric and periodic arrangement of atoms in a crystal is a basic theory of solid state physics and chemistry. The closed packed crystal structure under high pressure becomes extremely complicated. For example, the incommensurate structure which is rare at ambient pressure becomes common at high pressure. HPSTAR will conduct systematic research in this area to explore the new rules in crystallography.
Order-Disorder and Dimensions - In the late 20th century, crystallography expanded to 1D, 2D, 3D, short, medium and long-range ordered or disordered systems. Applying pressure provides the most effective mean to create and tune these structures. Many novel quasicrystals (2011 Nobel Prize) and liquid crystals would be discovered at high pressure.
Electronic Structure - “Free electron model” and “Energy band theory” are the basic and effective models for explaining conductivity phenomenon. Pressure can regulate electrons, which provides a new insight for electronics.
Magnetic Physics - Pressure has a critical impact on magnetic materials. It can regulate magnetic phenomena, such as magnetic ordering temperature, Curie temperature, magnetic domains and the arrangement of atomic magnetic moments. In addition, it can also tune the special magnetic phenomena which have important application value, such as magneto-optical effects, magneto caloric effects and magnetic resonance phenomenon.
Strongly Correlated Systems - A lot of interesting physical phenomena can be described by a collection of particles that interact with one another. In most cases, the interactions are strong enough to establish certain correlation between particles. These particles are called strongly correlated systems. These systems such as superconductor, Mott insulators, antiferromagnetic insulator, semiconductor, heavy fermion and giant magneto resistance, are the most important discoveries in condensed matter physics in the 20th century. Applying pressure can provide the purest mean to make substances across these boundaries. It also provides an opportunity to understand strongly correlated systems and explore the mechanism of high-temperature superconductivity.