Dr. Mitsuhiro Akatsu, Niigata University, Japan

Mitsuhiro Akatsu

I stayed at the Dresden High Magnetic Field Laboratory (HLD) from April 2012 until March 2013 in order to collaborate on ultrasonic studies of strongly correlated electron systems under high magnetic fields. The stay was generously supported by “the Strategic Young Researcher Overseas Visits Program for Accelerating Brain Circulation” from the Japan Society for the Promotion of Science.

My colleagues and I investigate iron-based superconductors of the type Ba(Fe1-xCox)2As2, the quasi-one dimensional spin system BaCo2V2O8, and some rare-earth compounds by using ultrasound measurements. When changing temperature, these compounds show a characteristic elastic softening (i.e., a reduction of the sound velocity), which is caused by quadrupolar or spin-fluctuation effects.  

When sweeping the magnetic field, we have observed fine structures in the elastic constants of BaCo2V2O8 and an elastic anomaly caused by a level crossing of crystal-electric-field ground states in PrAg2In at high magnetic fields. For Ba(Fe1-xCox)2As2, our high-field data suggest that quadrupolar fluctuations are robust against magnetic field. These results give us important information for a better understanding of the quantum states in these compounds. In the near future, we will publish these results.

It is important to examine new materials under high magnetic fields in order to deeply understand their physical properties. The Dresden High Magnetic Field Laboratory is well equipped with long-pulsed magnets and ultrasound measurement systems. These are very useful tools to study the quantum state, multipole effects, and lattice dynamics in strongly correlated electron compounds. I was able to smoothly perform pulse-field experiments by having great support from the HLD staff. I think that the HLD is one of the best research facilities for studying condensed-matter physics in high magnetic fields.