Magnetoresistance and de Haas-van Alphen Effect in CeRu₂Si₂and LaRu₂Si₂

Change of Fermi Surface Topology in CeRu2Si2 Studied by LSDA+U Method

“…10,11) The cyclotron effective masses also increase considerably around H m , [12][13][14] then the dHvA frequencies change abruptly at the critical magnetic field. Meanwhile, low-temperature magnetization measurements have confirmed that CeRu 2 Si 2 possess a finite crossover temperature to the Fermi-liquid ground state at H $ H m , 15) and a recent magnetoresistance measurements also show the absence of a discontinuity at the metamagnetic transition or hysteresis at the metamagnetic transition.…”

“…Meanwhile, the dHvA frequencies above H m can be explained well with the localized f electron picture, because of the similarity to the dHvA frequencies of LaRu 2 Si 2 . 11,12,14) Therefore, so far the electronic structure after the metamagnetic transition has been studied by treating the Ce-4f electrons as localized. 19) There has been no study based on an electronic structure calculation with treating the magnetic Ce-4f state for CeRu 2 Si 2 .…”

Probing the Fermi surface by positron annihilation and Compton scattering

“…De Haas-van Alphen experiments in CeRu 2 Si 2 (Ref. 69) at temperatures well below the Kondo temperature (T K $ 20 K) seemed to indicate that the f electrons were itinerant. As in CeIn 3 , five projections were measured at a temperature of 60 K (above T K ) with integration directions between the [100] and [110] crystallographic directions prior to tomographic reconstruction of the 3D momentum densities and then Fermi surfaces in both compounds.…”

“…This kind of shift (albeit for individual bands, rather than a global shift) was found to be necessary recently in Fermi surface measurements in the Fe-pnictide superconductors on the basis of quantum oscillations 70 and Compton scattering, 71 and has also been found to be necessary to accurately reproduce Fermi surfaces in other materials. 72,73 As Monge et al pointed out, however, if such shifts are necessary even without the complexities introduced by f electrons, it does call into question the assertion, based on such LDA calculations and dHvA data, 69,74 that the f electrons are itinerant in the heavy fermion state.…”

Dynamical Mean-Field Study of Metamagnetism in Heavy Fermion Systems

“…This is known as a "heavy fermion metamagnetism" and has been studied extensively in past decades. [1][2][3][4][5] To understand the physics of the heavy fermion systems including the metamagnetism from a microscopic viewpoint, we have to consider the effects of the c − f mixing and the strong correlation due to the Coulomb interaction between f electrons which are crucial for the heavy fermion properties. The Kondo lattice model (KLM) and periodic Anderson model (PAM) are fundamental models for studying the heavy fermion properties and many theoretical studies have been carried out on the basis of these models.…”