Strong Coupling between Antiferromagnetic and Superconducting Order Parameters in CeRhIn5_5 Studied by In-NQR Spectroscopy

We report on a novel pressure ($P$)-induced evolution of magnetism and superconductivity (SC) in a helical magnet CeRhIn$_5$ with an incommensurate wave vector $Q_i=({1/2},{1/2},0.297)$ through the $^{115}$In nuclear quadrupole resonance (NQR) measurements under $P$. Systematic measurements of the $^{115}$In-NQR spectrum reveal that the commensurate antiferromagnetism (AFM) with $Q_c=({1/2},{1/2},{1/2})$ is realized above $P_m \sim$ 1.7 GPa. An important finding is that the size of SC gap and $T_c$ increase as the magnitude of the AFM moment decreases in the $P$ region, where SC uniformly coexists with the commensurate AFM. This result provides evidence of strong coupling between the commensurate AFM order parameter (OP) and SC OP.Comment: 5 pages, 5 figure

Novel phase diagram for antiferromagnetism and superconductivity in pressure-induced heavy-fermion superconductor Ce2_2RhIn8_8 probed by In-NQR

We present a novel phase diagram for the antiferromagnetism and superconductivity in Ce$_2$RhIn$_8$ probed by In-NQR studies under pressure ($P$). The quasi-2D character of antiferromagnetic spin fluctuations in the paramagnetic state at $P$ = 0 evolves into a 3D character because of the suppression of antiferromagnetic order for $P > P_{\rm QCP}\sim$ 1.36 GPa (QCP: antiferromagnetic quantum critical point). Nuclear-spin-lattice-relaxation rate $1/T_1$ measurements revealed that the superconducting order occurs in the $P$ range 1.36 -- 1.84 GPa, with maximum $T_c\sim$ 0.9 K around $P_{\rm QCP}\sim$ 1.36 GPa.Comment: 5 pages, 5 figures, submitted to PR

Anomalous quasiparticle transport in the superconducting state of CeCoIn5

We report on a study of thermal Hall conductivity k_xy in the superconducting state of CeCoIn_5. The scaling relation and the density of states of the delocalized quasiparticles, both obtained from k_xy, are consistent with d-wave superconducting symmetry. The onset of superconductivity is accompanied by a steep increase in the thermal Hall angle, pointing to a striking enhancement in the quasiparticle mean free path. This enhancement is drastically suppressed in a very weak magnetic field. These results highlight that CeCoIn_5 is unique among superconductors. A small Fermi energy, a large superconducting gap, a short coherence length, and a long mean free path all indicate that CeCoIn_5 is clearly in the superclean regime (E_F/Delta<<l/xi), in which peculiar vortex state is expected.Comment: 5 pages, 5 figure

High Field de Haas - van Alphen Studies of the Fermi Surfaces of LaMIn5_{5} (M = Co, Rh, Ir)

We report measurements of the de Haas - van Alphen effect on a series of compounds, LaMIn$_{5}$ (M = Co, Rh, Ir). The results show that each of the Co and Ir Fermi surfaces (FSs) exhibit some portions that are two dimensional and some portions that are three dimensional. The most two dimensional character is exhibited in LaCoIn$_{5}$, less two dimensional behavior is seen in LaIrIn$_{5}$, no part of Fermi surface of LaRhIn$_{5}$ is found to have a two dimensional character. Thus the two dimensionality of portions of the FSs is largely determined by the d character of the energy bands while all of the effective masses remain $\leq$ 1.2. This fact has implications for the causes of the heavy fermion nature of superconductivity and magnetism in the Ce-based compounds having the similar composition and structure. All of the measurements were performed at the National High Magnetic Field Laboratory using either cantilever magnetometry or field modulation methods.Comment: 10 pages, 4 figure

Thermoelectric response near a quantum critical point: the case of CeCoIn5

We present a study of thermoelectric coefficients in CeCoIn_5 down to 0.1 K and up to 16 T in order to probe the thermoelectric signatures of quantum criticality. In the vicinity of the field-induced quantum critical point, the Nernst coefficient nu exhibits a dramatic enhancement without saturation down to lowest measured temperature. The dimensionless ratio of Seebeck coefficient to electronic specific heat shows a minimum at a temperature close to threshold of the quasiparticle formation. Close to T_c(H), in the vortex-liquid state, the Nernst coefficient behaves anomalously in puzzling contrast with other superconductors and standard vortex dynamics.Comment: 4 pages, 4 figures,final published versio

Competition between unconventional superconductivity and incommensurate antiferromagnetic order in CeRh1-xCoxIn5

Elastic neutron diffraction measurements were performed on the quasi-two dimensional heavy fermion system CeRh1-xCoxIn5, ranging from an incommensurate antiferromagnet for low x to an unconventional superconductor on the Co-rich end of the phase diagram. We found that the superconductivity competes with the incommensurate antiferromagnetic (AFM) order characterized by qI=(1/2, 1/2, delta) with delta=0.298, while it coexists with the commensurate AFM order with qc=(1/2, 1/2, 1/2). This is in sharp contrast to the CeRh1-xIrxIn5 system, where both the commensurate and incommensurate magnetic orders coexist with the superconductivity. These results reveal that particular areas on the Fermi surface nested by qI play an active role in forming the superconducting state in CeCoIn5.Comment: RevTeX4, 4 pages, 4 eps figures; corrected a typo and a referenc

^{115}In-NQR evidence for unconventional superconductivity in CeIn_3 under pressure

We report evidence for unconventional superconductivity in CeIn_3 at a pressure P = 2.65 GPa above critical pressure (P_c ~ 2.5 GPa) revealed by the measurements of nuclear-spin-lattice-relaxation time (T_1) and ac-susceptibility (ac-chi). Both the measurements of T_1 and ac-chi have pointed to a superconducting transition at T_c = 95 mK, which is much lower than an onset temperature T_{onset} = 0.15 K at zero resistance. The temperature dependence of 1/T_1 shows no coherence peak just below T_c, indicative of an unconventional nature for the superconductivity induced in CeIn_3.Comment: 4 pages, 4 figures, to be published in Phys.Rev.

Analysis of Foraging Behavior of Cattle Using a Wearable Camera under Diverse Vegetation

Although it is important to estimate the ingested plant species and the amount of forage intake by grazing animals, recording these items at the 1-bite scale has been difficult under diverse vegetation. Recent research confirmed that a small and inexpensive wearable camera is useful to determine ingested plant species and their proportion in total bites with high accuracy. In this study, we attempted to generate bite codes for cattle under diverse vegetation using wearable cameras. We used two cows which had a grazing experience in the previous year (GE) and the other two which had no grazing experience (NE). They grazed on a mountainous area (3 ha of sown pasture and 17 ha of forest) from late spring to mid-summer. A wearable camera (Panasonic HX-A500, 185 g) was fixed on the right cheek of the cows. Foraging behavior was continuously recorded for 120 min during morning foraging bouts, and direct observation was also conducted simultaneously. Bite codes were generated based on the morphological characteristics of ingested plants and the characteristics of foraging manner of the cows. Bite codes were classified into A (\u3e 100 cm), B (100–60 cm), and C (\u3c 60 cm) based on foraging height, then further classified into 5 types in A, 4 types in B, and 16 types in C (total 25 types) based on the differences in feeding manner. NE cows showed more frequent occurrence of the codes with low bite size than GE cows when foraging at a height of B in immediately after the start of grazing season. The results suggest that bite codes reflect bite size and thus can provide a precise understanding of their foraging behavior. It was also suggested that changes in bite codes due to the accumulation of grazing experience may affect foraging efficiency of grazing cattle