Coexistence Phase Of Antiferromagnetism Research Articles

Heat Capacity and Susceptibility of Rare Earth Magnetic Superconductors

We calculate the specific heat and susceptibility of rare earth magnetic superconductors in the context of the Ginzburg–Landau theory. The specific heat and susceptibility are calculated at both the coexistence phase of antiferromagnetism and superconductivity and normal phase. Theoretical results are compared with experimental results which agree excellently well.

Anomalous properties and coexistence of antiferromagnetism and superconductivity near a quantum critical point in rare-earth intermetallides

Mechanisms of the appearance of anomalous properties experimentally observed at the transition through the quantum critical point in rare-earth intermetallides have been studied. Quantum phase transitions are induced by the external pressure and are manifested as the destruction of the long-range antiferromagnetic order at zero temperature. The suppression of the long-range order is accompanied by an increase in the area of the Fermi surface, and the effective electron mass is strongly renormalized near the quantum critical point. It has been shown that such a renormalization is due to the reconstruction of the quasiparticle band, which is responsible for the formation of heavy fermions. It has been established that these features hold when the coexistence phase of antiferromagnetism and superconductivity is implemented near the quantum critical point.

Disorder Effects on Competition between Antiferromagnetism and Superconductivity in Cuprate Superconductors through the Enhancement in Charge Susceptibility

The coexistence state of antiferromagnetism (AF) and superconductivity (SC) has been observed in five-layered cuprates. However, this coexistence state disappears, and the AF phase and SC phase lose contact in the doping phase diagram toward double- and single-layered cuprates. We investigate the mechanism of the disappearance of the coexistence of AF and SC in disordered cuprate superconductors in order to understand these doping phase diagrams. In single- and double-layered cuprates, electrons on the CuO$_2$ plane experience the disorder effect through inhomogeneity in the charge reservoir layer. These impurity potentials can be effectively enhanced toward the underdoped region by the effect of many-body corrections that involve an increase in charge susceptibility. As a result, strong disorder effects are expected particularly in the competing regions of AF and SC, where the coexistence phase of AF and SC is extremely suppressed. We show the validity of this suppression mechanism by considering the Aslamazov-Larkin-type vertex correction to the effective impurity potential in the effective mean-field phase diagram.

Evidence for the first-order phase transition from antiferromagnetism to paramagnetism in CeRhIn 5

The systematic and comprehensive NQR experiments near P c are reported to address an intimate interplay between superconductivity (SC) and antiferromagnetism (AFM) of antiferromagnetic heavy-fermion compounds CeRhIn 5 via the nuclear-quadrupole-resonance (NQR) measurements under pressure ( P). The extensive measurements of In-NQR spectrum have revealed that a first-order transition occurs from the coexistent phase of AFM and SC to the single phase of SC at a critical pressure P c ≈ 2 GPa .

NMR/NQR Studies of Strongly Correlated Electron Systems

We report on an intimate interplay between superconductivity (SC) and antiferromagnetism (AFM) in CeRhIn5 under pressure and multilayered high-Tc cuprates via the NMR/NQR measurements. The experiments on CeRhIn5 has revealed that a first-order quantum phase transition (QPT) occurs around Pc-2 GPa from the AFM to the paramagnetism in the superconducting regime and the novel superconducting nature in the coexistent phase of AFM and SC. The site selective Cu-NMR study demonstrated that the under-doped five-layered high-Tc cuprate, HgBa2Ca4Cu5O12+δ with Tc=72 K can uniformly coexist on the microscopic level with the AFM. This is the first microscopic evidence for the uniform mixed phase of AFM and SC on a single CuO2 plane in a simple environment without any vortex lattice and/or stripe order.

Exotic Superconductivity in the Coexistent Phase of Antiferromagnetism and Superconductivity in CeCu2(Si0.98Ge0.02)2: A Cu-NQR Study under Hydrostatic Pressure

We report a pressure ($P$) effect on CeCu$_2$(Si$_{0.98}$Ge$_{0.02}$)$_2$ where an antiferromagnetic (AFM) order at $T_N \sim$ 0.75 K coexists with superconductivity below $T_c \sim$ 0.4 K\@. At pressures exceeding $P = 0.19$ GPa, the AFM order is suppressed, which demonstrates that the sudden emergence of AFM order due to the Ge doping is ascribed to the intrinsic lattice expansion. The exotic superconductivity at $P = 0$ GPa is found to evolve into a typical heavy-fermion one with a line-node gap above $P = 0.91$ GPa\@. We highlight that the anomalous enhancement in nuclear spin-lattice relaxation rate $1/T_1$ that follows a $T_1T$ = const. behavior well below $T_c$ at $P$ = 0 GPa is characterized by the persistence of low-lying magnetic excitations, which may be inherent to the coexistent state of antiferromagnetism and superconductivity.

Application of Berezinskii's Diagram Method to Bond Disordered System with the Dimerization and the Staggered Field

Based on the Berezinskii's diagram method, the density of states (DOS) of a bond disordered system has been calculated in the presence of the dimerization and the staggered field. It is found that the DOS near the center of the band behaves anomalously and that it is indicated that this feature is the cause of the coexistence phase of antiferromagnetism (AF) and dimerization in the disordered quasi-one-dimensional spin-Peierls (SP) system CuGe 1- y Si y O 3 .