We present the thermopower S (T) and the resistivity ρ (T) of Lu1-x Ybx Rh2 Si2 in the temperature range 3

We present measurements of the low temperature Hall effect and magnetoresistance in the heavy fermion superconductor CeCo(In 0.925Cd0.075)5 as a function of applied magnetic field. The Hall resistivity ρxy is observed to be negative indicating electron dominated transport. Features corresponding to the possible destabilization of the antiferromagnetic ground state are observed. Magnetic field sweeps show that the resistivity ρxx(H) is hysteretic in this regime, indicating that these transitions could be first order in nature. © 2009 IOP Publishing Ltd.

Hall effect measurements have been conducted on high-quality single crystals of the heavy-fermion superconductor CeCoIn5. The anomalous Hall contribution is negligible in the investigated temperature range from 0.05 to 5 K. The measured Hall resistivities ρxy show a noticeable change in slope between the low-field (initial Hall coefficient) and the high-field region. In the superconducting regime, T < 2.3 K, Hall measurements are restricted to high magnetic fields H > Hc 2, the upper critical field of superconductivity. The high-field Hall coefficient is almost constant for temperatures down to 250 mK. At T {less-than or slanted equal to} 250 mK, an additional change in curvature of ρxy vs. H is observed. © 2006 Elsevier B.V. All rights reserved.

We have investigated the electrodynamic response of the heavy-electron compounds UPd2Al3 (TN = 14.5 K) and UCu5 (TN = 15 K). The complete excitation spectra were obtained by Kramers-Kronig transformation of the optical reflectivities measured on a fairly broad frequency range (i.e. from 15 up to 105 cm-1), combined with the direct measurement of the conductivity at millimeter and microwave frequencies. In UCu5 we found an absorption in the far infrared below TN, which is ascribed to excitations across a spin-density-wave-type gap and indicates the itinerant nature of the magnetic phase transition. This feature is absent in UPd2Al3, in accordance with the local magnetic moment character of the antiferromagnetic order. © 1995.

High-quality single crystals of the heavy fermion superconductors CeCoIn5 and CeIrIn5 have been studied by means of low-temperature scanning tunneling microscopy. Methods were established to facilitate in situ sample cleaving. Spectroscopy in CeCoIn5 reveals a gap which persists to above Tc, possibly evidencing a precursor state to superconductivity. Atomically resolved topographs show a rearrangement of the atoms at the crystal surface. This modification at the surface might influence the surface properties as detected by tunneling spectroscopy. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

We present Hall effect and magnetoresistance measurements in the heavy fermion superconductor CeIrIn(5). At low temperature, a Kondo coherent state is established. Deviations from Kohler's rule and a quadratic temperature dependence of the cotangent of the Hall angle are reminiscent of properties observed in the high-temperature superconducting cuprates. A striking observation pertains to the presence of a precursor state--characterized by a change in the Hall mobility--that precedes the superconductivity in this material, in similarity to the pseudogap in the cuprate superconductors.

We report Hall Effect measurements under pressure in the normal state of CeCoIn5, from 60 to 355 mK and for fields exceeding the superconducting upper critical field Hc 2, with the field oriented parallel to [0 0 1]. At low pressures, the field dependence of the Hall coefficient exhibits a scaling consistent with the one reported in the normal state at higher temperatures, but at odds with the Δ H / T scaling expected near a field tuned quantum critical point. The breakdown of this scaling at higher pressures, concomitant with the suppression of spin fluctuations, suggests that it is a hallmark of the spin fluctuations.

We present low-temperature thermal expansion measurements on the nominally 10% Cd doped CeCoIn5. While the superconducting transition temperature is monotonically suppressed, an antiferromagnetic phase evolves in CeCoIn5 by Cd-doping. For the uniaxial pressure dependence of the Néel temperature along c, we find (∂ TN / ∂ p)∥ c = 0.206 K / GPa. The magnetic field dependence (for B ∥ c) of TN is stronger compared to CeRhIn5. As no traces of a superconducting transition are resolved in thermal expansion along the c-axis, we estimate a lower limit of the in-plane pressure dependence to (∂ Tc / ∂ p)⊥ c = 0.38 K / GPa. © 2007 Elsevier B.V. All rights reserved.

Topological insulators give rise to exquisite electronic properties because of their spin-momentum locked Dirac-cone-like band structure. Recently, it has been suggested that the required opposite parities between valence and conduction band along with strong spin-orbit coupling can be realized in correlated materials. Particularly, SmB₆ has been proposed as candidate material for a topological Kondo insulator. Here we observe, by utilizing scanning tunnelling microscopy and spectroscopy down to 0.35 K, several states within the hybridization gap of about ±20 meV on well characterized (001) surfaces of SmB₆. The spectroscopic response to impurities and magnetic fields allows to distinguish between dominating bulk and surface contributions to these states. The surface contributions develop particularly strongly below about 7 K, which can be understood in terms of a suppressed Kondo effect at the surface. Our high-resolution data provide insight into the electronic structure of SmB₆, which reconciles many current discrepancies on this compound.