Takao Ebihara

Fermi surface of the heavy-fermion superconductor CeCoIn5: The de Haas–van Alphen effect in the normal state

Measurements of the de Haas - van Alphen effect in the normal state of the heavy Fermion superconductor CeCoIn5 have been carried out using a torque cantilever at temperatures ranging from 20 to 500 mK and in fields up to 18 tesla. Angular dependent measurements of the extremal Fermi surface areas reveal a more extreme two dimensional sheet than is found in either CeRhIn5 or CeIrIn5. The effective masses of the measured frequencies range from 9 to 20 m*/m0.

Comment on the de Haas-van Alphen Effect in the Superconducting Mixed State of 2H–NbSe 2

We present the de Haas-van Alphen (dHvA) effect in the superconducting mixed state of 2H–NbSe 2 . Our data are consistent with the dHvA results obtained by Graebner and Robbins, which have been the subject of controversy from the viewpoint of experiment and theory. We discuss the reason why the theoretically expected cylindrical Fermi surfaces are not detected in the dHvA experiment and also the mechanism of the dHvA effect in the mixed state.

Kondo Lattice Effects of YbAl3 Suggested by Temperature Dependence of High-Accuracy High-Energy Photoelectron Spectroscopy

By use of high-resolution soft X-rays, intrinsic temperature dependences of bulk Yb 4f photoelectron spectra were obtained for fractured surfaces of high-purity YbAl 3 single crystals. The spectra ...

Heavy holes as a precursor to superconductivity in antiferromagnetic CeIn3.

Numerous phenomenological parallels have been drawn between f- and d- electron systems in an attempt to understand their display of unconventional superconductivity. The microscopics of how electrons evolve from participation in large moment antiferromagnetism to superconductivity in these systems, however, remains a mystery. Knowing the origin of Cooper paired electrons in momentum space is a crucial prerequisite for understanding the pairing mechanism. Of special interest are pressure-induced superconductors CeIn3 and CeRhIn5 in which disparate magnetic and superconducting orders apparently coexist—arising from within the same f-electron degrees of freedom. Here, we present ambient pressure quantum oscillation measurements on CeIn3 that crucially identify the electronic structure—potentially similar to high-temperature superconductors. Heavy hole pockets of f-character are revealed in CeIn3, undergoing an unexpected effective mass divergence well before the antiferromagnetic critical field. We thus uncover the softening of a branch of quasiparticle excitations located away from the traditional spin fluctuation-dominated antiferromagnetic quantum critical point. The observed Fermi surface of dispersive f-electrons in CeIn3 could potentially explain the emergence of Cooper pairs from within a strong moment antiferromagnet.

Pseudogap Formation and Heavy-Carrier Dynamics in Intermediate-Valence YbAl3

Infrared optical conductivity [σ(ω)] of the intermediate-valence compound YbAl 3 has been measured at temperatures 8–690 K to study its microscopic electronic structures. Despite the highly metallic characteristics of YbAl 3 , σ(ω) exhibits a clear pseudogap (strong depletion of spectral weight) of about 60 meV below 40 K. It also shows a strong mid-infrared peak centered at ∼0.25 eV. The energy-dependent effective mass and scattering rate of the carriers obtained from the data indicate the formation of a heavy-mass Fermi liquid. These characteristic results are discussed in terms of the hybridization states between the Yb 4 f and the conduction electrons. It is argued, in particular, that the pseudogap and the mid-infrared peak result from the indirect and direct gaps, respectively, within the hybridization state.

Magnetic and Electrical Properties of UPd3

We have measured the electrical resistivity, Hall coefficient, thermoelectric power, magnetic susceptibility, magnetization, specific heat, magnetoresistance and de Haas-van Alphen (dHvA) oscillation of UPd 3 to clarify the magnetic and Fermi surface properties. A phase transition, which occurs at about 4.5 K, is most likely related to the antiferromagnetic ordering because the magnetic specific heat shows a T 3 dependence below 2 K. About ten different dHvA branches ranging from 1.8 ×10 5 Oe to 7.5 ×10 7 Oe have been observed. From the angular dependence of dHvA frequency, UPd 3 is found to consist of the closed spherical Fermi surfaces and multiply-connected ones. The cyclotron masses are light, ranging from 0.5 m 0 to 3.6 m 0 , which indicate the localized f electron character.

Metamagnetic Transition in PrCu2 Studied by the de Haas-van Alphen Effect

We have observed a metamagnetic transition in PrCu 2 where a cooperative Jahn-Teller effect occurs below 8 K. This transition brings about a conversion between an easy and a hard axes in magnetization, which is reflected in a drastic change of the de Haas-van Alphen amplitude, that is a change of the scattering lifetime of conduction electrons. The origin of the metamagnetic transition is ascribed to a quadrupole moment of the 4 f level.

Fermi surface property of branch d in CeIn3

Abstract We have measured the de Haas-van Alphen effect of the heavy-electron compound CeIn 3 . The Fermi surface and the cyclotron mass of branch d are discussed.

Magnetoresistance and de Haas-van Alphen Effect in the Antiferromagnetic Compound NdIn 3

We have measured the magnetoresistance and de Haas-van Alphen (dHvA) effect in both the antiferromagnetic and paramagnetic states of NdIn 3 . Many dHvA branches are detected in the dHvA experiments. Among them, a nearly spherical Fermi surface in the paramagnetic state, which corresponds to a band 7-electron Fermi surface of the non-4 f reference compound LaIn 3 , is changed in the antiferromagnetic state into a multiply connected Fermi surface with necks. The cyclotron masses of NdIn 3 are in the range of 0.30 m 0 to 1.05 m 0 , which are twice as large as those of LaIn 3 .

Dependence of the effective masses in YbAl3 on magnetic field and disorder

We show for the intermediate valence compound YbAl