Seminarium Oddziału Badań Magnetyków

Study of magnetic quantum phase transitions using Mössbauer Spectroscopy

prof. Mohsen M. Abd-Elmeguid

II Instytut Fizyki Uniwersytetu Kolońskiego w Kolonii w Niemczech

Quantum phase transitions (QPT) are phase transitions at zero temperature which can be triggered by a non-thermal parameter such as pressure, chemical substitution, or magnetic field. They are driven by a corresponding change of quantum fluctuations between phases across a quantum critical point (QCP). Particularly interesting is the fact that these fluctuations strongly affect the physical properties of the system at finite temperature, resulting unusual low temperature behavior and the formation of new ground states including unconventional superconductivity.

In this talk I first will give a brief and simple introduction to quantum phase transitions and the associated novel phenomena near a quantum critical point. I, then, focus on how external pressure can be used to tune the properties of selected systems across a QPT and show how ¹⁵¹Eu high pressure Mössbauer spectroscopy in different magnetically ordered Eu compounds (EuCo₂P₂, EuCu₂(Ge_1-xSi_x)₂, and EuNiO₃)  can be used to obtain at a microscopic level valuable information  about the nature of novel ground states at/near a QCP.