L. Taillefer — Page 3

arXiv1996

Influence of a magnetic field on the antiferromagnetic order in UPt_3

A neutron diffraction experiment was performed to investigate the effect of a magnetic field on the antiferromagnetic order in the heavy fermion superconductor UPt_3. Our results show that a field in the basal plane of up to 3.2 Tesla, higher than H_c2(0), has no effect: it can neither select a domain nor rotate the moment. This has a direct impact on current theories for the superconducting phase diagram based on a coupling to the magnetic order.

cond-mat↗

arXiv1996

Low temperature thermal conductivity of Zn-doped YBCO: evidence for impurity-induced electronic bound states

The thermal conductivity of Zn-doped YBCO crystals was studied at low temperature (0.15 < T < 0.8 K) for different concentrations of Zn impurities. A small amount of Zn induces a dramatic decrease in the non-linear component of the low-temperature thermal conductivity. Moreover, the magnitude of the linear component (obtained by extrapolating the data to T=0) is found to depend on Zn concentration. After an initial decrease, this linear term, associated with the electronic contribution to the conductivity, increases with increasing Zn dopage. Such an increase is consistent with the introduction of low-energy excitations by Zn impurities as expected for a $d_{x^2-y^2}$ superconducting state in contrast to an anisotropic s-wave gap. The results are compared to quantitative predictions of available theoretical models.

supr-con↗