Thermal Conductivity through the Quantum Critical Point in YbRh_{2}Si_{2} at Very Low Temperature

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Critical Phenomena

Background:

• Ytterbium rhodium disilicide (YbRh_{2}Si_{2}) is a well-known heavy fermion system exhibiting quantum criticality.
• Understanding heat transport mechanisms in such materials is crucial for exploring novel electronic states.

Purpose of the Study:

• To investigate the thermal conductivity of YbRh_{2}Si_{2} at extremely low temperatures.
• To identify the origin of an additional heat transport channel observed below 30 mK.
• To assess the implications for the Wiedemann-Franz law near a field-induced quantum critical point.

Main Methods:

• Low-temperature measurements of thermal conductivity.
• Application of magnetic fields in the basal plane.
• Analysis of heat transport in both antiferromagnetic and paramagnetic states.

Main Results:

• An additional channel for heat transport was observed below 30 mK.
• This phenomenon occurred in both antiferromagnetic and paramagnetic states, above and below the critical field.
• Antiferromagnetic magnons were ruled out as the source of this additional thermal conductivity.

Conclusions:

• The observed low-temperature heat transport is not due to antiferromagnetic magnons.
• Further investigation is needed to determine the exact nature of this new transport channel.
• The findings provide critical data for understanding the validity of the Wiedemann-Franz law at field-induced quantum critical points.