High Pressure Physics
Projektleiter: Dr. Alexander Drozdov
Team Member: Dr. Feng Du
We investigate the frontiers of condensed matter physics by putting materials to the highest static pressures that can be reached in a laboratory.
By compressing materials to pressures above those found at Earth’s core, we place atoms in new arrangements and thereby change their electronic and structural properties in a controlled way.
Our primary mission is the search for and characterisation of novel quantum states of matter, with a specific focus on metallic hydrogen and high-temperature superconductivity.
Research Focus
The Quest for Metallic Hydrogen
One of the longest-standing challenges in physics is the metallisation of hydrogen. While optical changes - such as the sample turning black or reflective - can hint at phase transitions, they do not guarantee an actual metallic state. To overcome this ambiguity, we employ direct electrical transport measurements to probe hydrogen’s properties at the limit of current experimental capabilities.
We are among the few teams capable of measuring temperature-dependent electrical resistance at pressures of 300–400 GPa or higher. This allows us to distinguish between a narrow-gap semiconductor and a true metal, providing direct and convincing evidence of the insulator-to-metal transition.
High-Tc Superconducting Hydrides
Building on the discovery of conventional superconductivity at record temperatures, we synthesise and characterise hydrogen-rich materials (superhydrides). Our work includes the investigation of systems such as sulfur hydrides (H3S) and rare-earth hydrides (e.g., LaH10), which have demonstrated critical temperatures close to room temperature. We aim to understand the mechanisms of superconductivity in these systems and push the critical temperature even higher.
Methodologies & Expertise
High Pressure
We are among the few teams worldwide capable of routinely generating the highest static pressures (megabar range) using diamond anvil cells (DACs). Unlike standard high-pressure setups, our expertise lies in performing complex, high-precision in situ measurements under these extreme conditions.
Advanced Tunnelling Spectroscopy (Specialised Expertise)
A cornerstone of our team‘s technical capability is the development of planar tunnel junctions and Andreev reflection spectroscopy for the diamond anvil cell, techniques pioneered and refined by Dr Feng Du.
While standard resistance measurements show when a material becomes superconducting - tunnelling spectroscopy gives us a microscopic view and helps us understand why and how it happens.
. By fabricating intricate tunnelling barriers directly on the diamond anvil culet, we can:
- Directly Measure the Superconducting Gap: We have successfully resolved the energy gap in high-pressure superconductors such as Sulfur and Hydrogen Sulfide (H3S) at megabar pressures.
- Confirm Pairing Mechanisms: Our tunnelling data on H3S and D3S provide crucial evidence for the electron-phonon coupling mechanism, confirming theoretical predictions.
- Probe Density of States: This technique allows us to probe the electronic density of states (DOS) and verify the s-wave nature of these superconductors and not the unconventional one.
Complementary Techniques
- Electrical Transport: Precise resistivity measurements to detect superconducting transitions and measure zero resistance.
- Magnetic Measurements: AC and DC magnetic susceptibility to confirm the Meissner effect in microscopic samples.
- Optical Spectroscopy: Raman and Infrared spectroscopy to monitor structural evolution and bonding changes under pressure.
Our Heritage
The team is built upon a foundation of world-class expertise. Both Alexander Drozdov and Feng Du were trained by and worked extensively with Mikhail Eremets, a pioneer in high-pressure physics. This mentorship has provided our team with deep technical knowledge in high-pressure cell preparation, high-pressure electrical measurements, and the interpretation of data measured at the limits of current measurement capabilities. We continue to maintain this high standard of experimental rigour in our independent research.