arXiv subjects

C. Capan

Publications and source records attributed to C. Capan.

24 records · Page 2Linked to original sources

arXiv2004

Non-Fermi Liquid behavior in CeIrIn$_5$ near a metamagnetic transition

We present specific heat and resistivity study of CeIrIn5 in magnetic fields up to 17 T and temperature down to 50 mK. Both quantities were measured with the magnetic field parallel to the c-axis (H || [001]) and within the a-b plane (H \perp [001]). Non-Fermi-liquid (NFL) behavior develops above 12 T for H || [001]. The Fermi liquid state is much more robust for H \perp [001] and is suppressed only moderately at the highest applied field. Based on the observed trends and the proximity to a metamagnetic phase transition, which exists at fields above 25 T for H || [001], we suggest that the observed NFL behavior in CeIrIn5 is a consequence of a metamagnetic quantum critical point.

cond-mat.str-el↗

arXiv2004

Anisotropy of Thermal Conductivity and Possible Signature of the Fulde-Ferrell-Larkin-Ovchinnikov state in CeCoIn_5

We have measured the thermal conductivity of the heavy-fermion superconductor CeCoIn_5 in the vicinity of the upper critical field, with the magnetic field perpendicular to the c axis. Thermal conductivity displays a discontinuous jump at the superconducting phase boundary below critical temperature T_0 ~ 1 K, indicating a change from a second to first order transition and confirming the recent results of specific heat measurements on CeCoIn_5. In addition, the thermal conductivity data as a function of field display a kink at a field H_k below the superconducting critical field, which closely coincides with the recently discovered anomaly in specific heat, tentatively identified with the appearance of the spatially inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconducting state. Our results indicate that the thermal conductivity is enhanced within the FFLO state, and call for further theoretical investigations of the order parameter's real space structure (and, in particular, the structure of vortices) and of the thermal transport within the inhomogeneous FFLO state.

cond-mat.str-el↗

arXiv2003

Fulde-Ferrell-Larkin-Ovchinnikov Superconducting State in CeCoIn5

We report specific heat measurements of the heavy fermion superconductor CeCoIn5 in the vicinity of the superconducting critical field H_{c2}, with magnetic field in the [110], [100], and [001] directions, and at temperatures down to 50 mK. The superconducting phase transition changes from second to first order for field above 10 T for H || [110] and H || [100]. In the same range of magnetic field we observe a second specific heat anomaly within the superconducting state. We interpret this anomaly as a signature of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) inhomogeneous superconducting state. We obtain similar results for H || [001], with FFLO state occupying a smaller part of the phase diagram.

cond-mat.str-el↗

arXiv2002

Anomalous dissipation in the mixed state of underdoped cuprates close to the superconductor-insulator boundary

We present a comparative study of Nernst effect and resistivity in underdoped samples of Bi$_2$Sr$_2$CuO$_{6+δ}$ and La$_{2-x}$Sr$_{x}$CuO$_4$. The Nernst effect presents a peak in a region of the H-T diagram where resistivity shows a non-metallic temperature dependence. Our results illustrate that the mechanism of dissipation in the mixed state of underdoped cuprates is poorly understood. Large quantum superconducting fluctuations and vanishing vortex viscosity are among suggested explanations for an enhanced Nernst signal close to the superconductor-insulator boundary.

cond-mat.supr-con↗

arXiv2001

Entropy of vortex cores on the border of the superconductor-to-insulator transition in an underdoped cuprate

We present a study of Nernst effect in underdoped $La_{2-x}Sr_xCuO_4$ in magnetic fields as high as 28T. At high fields, a sizeable Nernst signal was found to persist in presence of a field-induced non-metallic resistivity. By simultaneously measuring resistivity and the Nernst coefficient, we extract the entropy of vortex cores in the vicinity of this field-induced superconductor-insulator transition. Moreover, the temperature dependence of the thermo-electric Hall angle provides strong constraints on the possible origins of the finite Nernst signal above $T_c$, as recently discovered by Xu et al.

cond-mat.supr-con↗

arXiv1999

Internal avalanches in a pile of superconducting vortices

Using an array of miniature Hall probes, we monitored the spatiotemporal variation of the internal magnetic induction in a superconducting niobium sample during a slow sweep of external magnetic field. We found that a sizable fraction of the increase in the local vortex population occurs in abrupt jumps. The size distribution of these avalanches presents a power-law collapse on a limited range. In contrast, at low temperatures and low fields, huge avalanches with a typical size occur and the system does not display a well-defined macroscopic critical current.

cond-mat.supr-con↗