Abstract
We present band structure calculations and quantum oscillation measurements on LuRh2Si2, which is an ideal reference to the intensively studied quantum critical heavy-fermion system YbRh2Si2. Our band structure calculations show a strong sensitivity of the Fermi surface on the position of the silicon atoms zSi within the unit cell. Single crystal structure refinement and comparison of predicted and observed quantum oscillation frequencies and masses yield zSi = 0.379 c in good agreement with numerical lattice relaxation.This value of zSi is suggested for future band structure calculations on LuRh2Si2 and YbRh2Si2. LuRh2Si2 with a full f electron shell represents the ‘small’ Fermi surface configuration of YbRh2Si2. Our experimentally and ab intio derived quantum oscillation frequencies of LuRh2Si2 differ significantly from the results of earlier measurements on YbRh2Si2. Consequently, our results confirm the contribution of the f electrons to the Fermi surface of YbRh2Si2 at high magnetic fields. Yet, the limited agreement with refined fully itinerant local density approximation calculations highlights the need for more elaborate models to describe the Fermi surface of YbRh2Si2.
Highlights
Of the Fermi surface which is not expected at a QCP where the magnetic order parameter evolves continuously
When tuning across the QCP towards the suggested ‘small’ Fermi surface configuration, i.e. from large fields to low fields, the Hall coefficient crossover in YbRh2Si2 has a trend towards the Hall coefficient of LuRh2Si2 with its value increasing in the direction of the even larger value observed in LuRh2Si2 [4]
The nomenclature of the frequencies reflects the assignment to orbits on the different Fermi surface sheets, which we deduce from the comparison with band structure calculations below
Summary
Of the Fermi surface which is not expected at a QCP where the magnetic order parameter evolves continuously. Renormalized band structure calculations suggest nonlinear dependences of the Fermi surface cross sections in magnetic field [17] which lead to changing frequencies in quantum oscillation measurements. The lack of agreement between the measured frequencies and those expected from LDA calculations within a ‘large’ Fermi surface scenario may be attributed to the known shortcomings of LDA calculations in Yb-based heavy fermion materials. The Fe–As–Fe angle which is an equivalent measure of the same Wyckoff parameter zSi is crucial for the nesting of the Fermi surface sheets and for the optimum superconducting transition temperature [1, 22] These findings for other members of the ThCr2Si2 structure family underpin the need to precisely determine the Si position for LuRh2Si2 and YbRh2Si2 and its significance for their electronic structure. We find even stronger differences between the experimental results on YbRh2Si2 and our refined ‘small’ Fermi surface calculations
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