Cyclotron resonance in rare-earth monopnictides

Abstract

Recently, we have developed equipment which can be used for both cyclotron resonance ͑CR͒ and electron spin resonance ͑ESR͒ measurements for studying f-electron systems. Using this equipment and preparing high-quality single crystals with a residual resistivity ratio of about 500, we have successfully observed CR signals in rare-earth monopnictides RX ͑R =La,Ce,Pr,Gd,X =Sb,Bi͒. The purpose of this paper is to describe the development of our measurement system in detail and to reexamine our recent results of CR measurements on the single crystals of RX. And then, we discuss the origin of mass enhancement in this system by comparing the case of a strongly correlated f-electron system CeSb with the case of a nonmagnetic simple semimetal LaSb. The CR measurements have been performed in the temperature range from 1.4 K to 40 K and in the frequency range from 50 to 190 GHz. We have observed CR signals in LaSb, LaBi, CeSb, PrSb, and GdSb. The cyclotron effective masses m CR * determined by the CR measurements are compared with the masses m QO * estimated by measurements of quantum oscillations and the masses m BC * deduced from band structure calculations. The determined m CR * of LaSb, LaBi, and GdSb is in the range of ͑0.17-0.65͒m 0 . These values are reasonably consistent with the values of m QO * and m BC * . This fact shows that both m CR * and m QO * mainly depend on the band structure if the interaction between conduction electrons and f electrons is negligible. On the other hand, in the case of a strongly correlated f-electron system CeSb, m CR * is in the range of ͑0.26-1.5͒m 0 . These values are much larger than those of m BC * . This finding shows that m CR * , as well as m QO * , is considerably enhanced in CeSb. Our results indicate that the interband interaction is important for the mass enhancement of m CR * in CeSb.

Fermi surface topology and signature of surface Dirac nodes in LaBi

“…However, the difference in the number of Fermi pockets, probed in these two methods, can not be explained from such arguments. There are several reports on cyclotron resonance experimental and theoretical works for LaBi and isostructural compound LaSb, as these are quite old systems 38 – 41 . Moreover, dHvA oscillation has been studied in LaSb 42 .…”

Cyclotron Resonance in the Hidden-Order Phase ofURu2Si2

“…¼ 2f is the microwave angular frequency and H CR is the resonance field. It should be noted that in one-component translationally invariant systems m à CR is not renormalized by the electron-electron interaction (Kohn's theorem [22]), but in solids this theorem can be violated [23] especially for the heavy-fermion systems with interacting conduction and f electrons [24] and for multiband systems [25,26]. Therefore, the momentum dependence of m à CR in each FS should contain important information on the electron correlations, which sometimes are a source of emergent novel phases.…”

Correlation-Enhanced Effective Mass of Two-Dimensional Electrons inMgxZn1−xO/ZnOHeterostructures

“…Therefore, a comparison between m à CR and m à tr can be a unique tool of gauging the magnitude of the correlation effects. We wish to point out, however, that the theorem for CR can be violated especially for multiband systems [8,9]. The 2DESs in the Mg x Zn 1Àx O=ZnO heterostructures offer an ideal platform for the comparative study, since the electrons in this novel structure occupy an isotropic single pocket with a large band mass in contrast with the other 2DESs having complex band structures and/or light electron masses.…”