Tuning the Pairing Interaction in a d-Wave Superconductor by Paramagnons Injected through Interfaces.

Unconventional superconductivity and magnetism are intertwined on a microscopic level in a wide class of materials. A new approach to this most fundamental and hotly debated issue focuses on the role of interactions between superconducting electrons and bosonic fluctuations at the interface between adjacent layers in heterostructures. Here we fabricate hybrid superlattices consisting of alternating atomic layers of the heavy-fermion superconductor CeCoIn_{5} and antiferromagnetic (AFM) metal CeRhIn_{5}, in which the AFM order can be suppressed by applying pressure. We find that the superconducting and AFM states coexist in spatially separated layers, but their mutual coupling via the interface significantly modifies the superconducting properties. An analysis of upper critical fields reveals that, upon suppressing the AFM order by applied pressure, the force binding superconducting electron pairs acquires an extreme strong-coupling nature. This demonstrates that superconducting pairing can be tuned nontrivially by magnetic fluctuations (paramagnons) injected through the interface.

Electronic nematicity above the structural and superconducting transition in BaFe2(As(1-x)P(x))2.

Electronic nematicity, a unidirectional self-organized state that breaks the rotational symmetry of the underlying lattice, has been observed in the iron pnictide and copper oxide high-temperature superconductors. Whether nematicity plays an equally important role in these two systems is highly controversial. In iron pnictides, the nematicity has usually been associated with the tetragonal-to-orthorhombic structural transition at temperature T(s). Although recent experiments have provided hints of nematicity, they were performed either in the low-temperature orthorhombic phase or in the tetragonal phase under uniaxial strain, both of which break the 90° rotational C(4) symmetry. Therefore, the question remains open whether the nematicity can exist above T(s) without an external driving force. Here we report magnetic torque measurements of the isovalent-doping system BaFe(2)(As(1-x)P(x))(2), showing that the nematicity develops well above T(s) and, moreover, persists to the non-magnetic superconducting regime, resulting in a phase diagram similar to the pseudogap phase diagram of the copper oxides. By combining these results with synchrotron X-ray measurements, we identify two distinct temperatures-one at T*, signifying a true nematic transition, and the other at T(s) (

Tuning the Magnetic Quantum Criticality of Artificial Kondo Superlattices CeRhIn_{5}/YbRhIn_{5}.

The effects of reduced dimensions and the interfaces on antiferromagnetic quantum criticality are studied in epitaxial Kondo superlattices, with alternating n layers of heavy-fermion antiferromagnet CeRhIn_{5} and seven layers of normal metal YbRhIn_{5}. As n is reduced, the Kondo coherence temperature is suppressed due to the reduction of effective Kondo screening. The Néel temperature is gradually suppressed as n decreases and the quasiparticle mass is strongly enhanced, implying dimensional control toward a quantum critical point. Magnetotransport measurements reveal that a quantum critical point is reached for the n=3 superlattice by applying small magnetic fields. Remarkably, the anisotropy of the quantum critical field is opposite to the expectations from the magnetic susceptibility in bulk CeRhIn_{5}, suggesting that the Rashba spin-orbit interaction arising from the inversion symmetry breaking at the interface plays a key role for tuning the quantum criticality in the two-dimensional Kondo lattice.

Observation of orbital resonance Hall effect in (TMTSF)2ClO4.

We report the observation of a Hall effect driven by orbital resonance in the quasi-1-dimensional (q1D) organic conductor (TMTSF)2ClO4. Although a conventional Hall effect is not expected in this class of materials due to their reduced dimensionality, we observed a prominent Hall response at certain orientations of the magnetic field B corresponding to lattice vectors of the constituent molecular chains, known as the magic angles (MAs). We show that this Hall effect can be understood as the response of conducting planes generated by an effective locking of the orbital motion of the charge carriers to the MA driven by an electron-trajectory resonance. This phenomenon supports a class of theories describing the rich behavior of MA phenomena in q1D materials based on altered dimensionality. Furthermore, we observed that the effective carrier density of the conducting planes is exponentially suppressed in large B, which indicates possible density wave formation.

Controllable Rashba spin-orbit interaction in artificially engineered superlattices involving the heavy-fermion superconductor CeCoIn5.

By using a molecular beam epitaxy technique, we fabricate a new type of superconducting superlattices with controlled atomic layer thicknesses of alternating blocks between the heavy-fermion superconductor CeCoIn5, which exhibits a strong Pauli pair-breaking effect, and nonmagnetic metal YbCoIn5. The introduction of the thickness modulation of YbCoIn5 block layers breaks the inversion symmetry centered at the superconducting block of CeCoIn5. This configuration leads to dramatic changes in the temperature and angular dependence of the upper critical field, which can be understood by considering the effect of the Rashba spin-orbit interaction arising from the inversion symmetry breaking and the associated weakening of the Pauli pair-breaking effect. Since the degree of thickness modulation is a design feature of this type of superlattices, the Rashba interaction and the nature of pair breaking are largely tunable in these modulated superlattices with strong spin-orbit coupling.

Evidence for a finite-momentum Cooper pair in tricolor d-wave superconducting superlattices.

Fermionic superfluidity with a nontrivial Cooper-pairing, beyond the conventional Bardeen-Cooper-Schrieffer state, is a captivating field of study in quantum many-body systems. In particular, the search for superconducting states with finite-momentum pairs has long been a challenge, but establishing its existence has long suffered from the lack of an appropriate probe to reveal its momentum. Recently, it has been proposed that the nonreciprocal electron transport is the most powerful probe for the finite-momentum pairs, because it directly couples to the supercurrents. Here we reveal such a pairing state by the non-reciprocal transport on tricolor superlattices with strong spin-orbit coupling combined with broken inversion-symmetry consisting of atomically thin d-wave superconductor CeCoIn5. We find that while the second-harmonic resistance exhibits a distinct dip anomaly at the low-temperature (T)/high-magnetic field (H) corner in the HT-plane for H applied to the antinodal direction of the d-wave gap, such an anomaly is absent for H along the nodal direction. By carefully isolating extrinsic effects due to vortex dynamics, we reveal the presence of a non-reciprocal response originating from intrinsic superconducting properties characterized by finite-momentum pairs. We attribute the high-field state to the helical superconducting state, wherein the phase of the order parameter is spontaneously spatially modulated.

Kosterlitz-Thouless-type transition in a charge ordered state of the layered organic conductor α-(BEDT-TTF)2I3.

The current-voltage characteristics in the charge order state of the two-dimensional organic conductor α-(BEDT-TTF)(2)I(3) exhibit power law behavior at low temperatures. The power law is understood in terms of the electric-field-dependent potential between electrons and holes, which are thermally excited from the charge order state. The power law exponent steeply changes from 1 to 3 in the range from 30 to 45 K with decreasing temperature, thereby suggesting the occurrence of a Kosterlitz-Thouless-type transition; many (few) unbound electron-hole pairs are thermally excited above (below) the transition. The effects of the finite size and interlayer coupling on the power law behavior are discussed.

Nodal versus nodeless behaviors of the order parameters of LiFeP and LiFeAs superconductors from magnetic penetration-depth measurements.

High-precision measurements of magnetic penetration depth λ in clean single crystals of LiFeAs and LiFeP superconductors reveal contrasting behaviors. In LiFeAs the low-temperature λ(T) shows a flat dependence indicative of a fully gapped state, which is consistent with previous studies. In contrast, LiFeP exhibits a T-linear dependence of superfluid density infinity λ(-2), indicating a nodal superconducting order parameter. A systematic comparison of quasiparticle excitations in the 1111, 122, and 111 families of iron-pnictide superconductors implies that the nodal state is induced when the pnictogen height from the iron plane decreases below a threshold value of ~1.33 Å.

de Haas-van Alphen study of the Fermi surfaces of superconducting LiFeP and LiFeAs.

We report a de Haas-van Alphen oscillation study of the 111 iron pnictide superconductors LiFeAs with T(c) ≈ 18 K and LiFeP with T(c) ≈ 5 K. We find that for both compounds the Fermi surface topology is in good agreement with density functional band-structure calculations and has almost nested electron and hole bands. The effective masses generally show significant enhancement, up to ~3 for LiFeP and ~5 for LiFeAs. However, one hole Fermi surface in LiFeP shows a very small enhancement, as compared with its other sheets. This difference probably results from k-dependent coupling to spin fluctuations and may be the origin of the different nodal and nodeless superconducting gap structures in LiFeP and LiFeAs, respectively.

Anomalous upper critical field in CeCoIn5/YbCoIn5 superlattices with a Rashba-type heavy Fermion interface.

We report a highly unusual angular variation of the upper critical field (H(c2)) in epitaxial superlattices CeCoIn(5)(n)/YbCoIn(5)(5), formed by alternating layers of n and a 5 unit-cell thick heavy-fermion superconductor CeCoIn(5) with a strong Pauli effect and normal metal YbCoIn(5), respectively. For the n=3 superlattice, H(c2)(θ) changes smoothly as a function of the field angle θ. However, close to the superconducting transition temperature, H(c2)(θ) exhibits a cusp near the parallel field (θ=0°). This cusp behavior disappears for n=4 and 5 superlattices. This sudden disappearance suggests the relative dominance of the orbital depairing effect in the n=3 superlattice, which may be due to the suppression of the Pauli effect in a system with local inversion symmetry breaking. Taking into account the temperature dependence of H(c2)(θ) as well, our results suggest that some exotic superconducting states, including a helical superconducting state, might be realized at high magnetic fields.

Infrared measurement of the pseudogap of P-doped and Co-doped high-temperature BaFe2As2 superconductors.

We report on infrared studies of charge dynamics in a prototypical pnictide system: the BaFe2As2 family. Our experiments have identified hallmarks of the pseudogap state in the BaFe2As2 system that mirror the spectroscopic manifestations of the pseudogap in the cuprates. The magnitude of the infrared pseudogap is in accord with that of the spin-density-wave gap of the parent compound. By monitoring the superconducting gap of both P- and Co-doped compounds, we find that the infrared pseudogap is unrelated to superconductivity. The appearance of the pseudogap is found to correlate with the evolution of the antiferromagnetic fluctuations associated with the spin-density-wave instability. The strong-coupling analysis of infrared data further reveals the interdependence between the magnetism and the pseudogap in the iron pnictides.

Comparison of chemotherapeutic treatment outcomes of advanced extrapulmonary neuroendocrine carcinomas and advanced small-cell lung carcinoma.

BACKGROUND: The chemotherapy for small-cell lung carcinoma (SCLC) has been adopted for advanced extrapulmonary neuroendocrine carcinomas (EP-NECs). The aim of this study was to clarify the efficacy of standard SCLC regimens when used to treat EP-NECs and to compare the outcome with that for SCLC. METHODS: We reviewed the medical records of 136 patients (41 with EP-NEC and 95 with SCLC) who were treated using a platinum-containing regimen for advanced disease between January 2000 and October 2008 at our hospital. RESULTS: The primary site of the EP-NEC was the gastrointestinal tract in 18 patients (GI tract group); the liver, biliary tract or pancreas in 16 patients (HBP group), and other sites in 7 patients ('others' group). The response rate in the SCLC patients was 77.8%, and the response rate in the EP-NEC patients was 30.8% (37.5% in the GI tract group, 12.5% in the HBP group, and 57.1% in the 'others' group). The median survival time for the SCLC patients was 13.6 months, while that for the EP-NEC patients was 9.2 months (14.9 months in the GI tract group, 7.8 months in the HBP group, and 8.9 months in the 'others' group). A multivariate analysis demonstrated that a poor performance status, liver involvement, and the treatment regimen were independent unfavorable prognostic factors. CONCLUSION: The response rate and prognosis of the patients with advanced EP-NECs were worse than those of the patients with SCLC in this study. The Eastern Cooperative Oncology Group performance status, liver involvement, and treatment regimen had a larger impact on the prognosis than the primary tumor site, as demonstrated by multivariate analysis.

Lipopolysaccharide induces rapid loss of follicular dendritic cell-secreted protein in the junctional epithelium.

UNLABELLED: Oshiro A, Iseki S, Miyauchi M, Terashima T, Kawaguchi Y, Ikeda Y, Shinomura T. Lipopolysaccharide induces rapid loss of follicular dendritic cell-secreted protein in the junctional epithelium. J Periodont Res 2012; 47: 689-694. © 2012 John Wiley & Sons A/S Background and Objective: We have previously reported that mRNA encoding follicular dendritic cell-secreted protein (FDC-SP) is expressed specifically in the junctional epithelium at the gingival crevice. Other tissues, such as tonsil, prostate gland and trachea, also express high levels of FDC-SP. These tissues participate in a range of functions closely related to innate immunity. Therefore, it is hypothesized that FDC-SP plays a crucial role in close association with the host defense system within the gingival crevice. Accordingly, the main aim of this study was to investigate the expression and localization of FDC-SP in and around the junctional epithelium and to observe the dynamic changes of FDC-SP in experimental inflammation. MATERIAL AND METHODS: We examined, immunohistochemically, the expression of FDC-SP in the junctional epithelium using a specific antibody raised in rabbit after immunization with a synthetic peptide derived from the hydrophilic region of FDC-SP. Experimental inflammation was induced in the upper molars of Wistar rats by applying bacterial lipopolysaccharide (LPS; 5 mg/mL in sterile saline) for 1 h. RESULTS: We confirmed that FDC-SP is present in the junctional epithelium in a pattern that is consistent with the expression of FDC-SP mRNA. Of special interest is that no FDC-SP was detectable in the junctional epithelium 3 h after transient topical treatment with LPS. CONCLUSION: The presence of FDC-SP in the junctional epithelium and its loss after LPS treatment strongly support our hypothesis of FDC-SP playing a crucial role in close association with the host defense system within the gingival crevice.

Anatomical evaluation of facial nerve pathways and dissection of "premasseter space" for rhytidectomy in Asians.

BACKGROUND: Partial detachment of the superficial musculoaponeurotic system (SMAS) by dissection of the premasseter space (PMS) is an option for enhancing the effectiveness of SMAS-based rhytidectomy. The aim of this study was to identify the underlying cause of the potential risk of motor nerve impairment sometimes caused by PMS dissection and to consider the effective use of PMS dissection, especially in Asians. METHODS: Detailed dissection was carried out on six fixed Japanese cadavers to evaluate facial nerve pathways around the PMS. RESULTS: The anterior wall of the PMS was opaque because each face exhibited fibers of various thicknesses within and around the anterior border of the masseter. The ascending ramifications of the buccal trunk ran through the fibers, outside the anterior border of the masseter in some faces but within it in others. CONCLUSIONS: This study revealed the presence of a danger zone when dissecting the PMS in Asians. Severing the fibers that fix the SMAS to the masseter fascia around the anterior border of the masseter is sometimes unavoidable to attain good mobility of the SMAS. Surgeons must be mindful of the fibers near the anterior border of the masseter because they may be outside the PMS and contain buccal trunk ramifications; the anterior wall of the PMS tends to be opaque in Asians. Nonetheless, the extent of PMS dissection should be determined on an individual basis. The present findings may help to reduce relevant risks in Asian patients and standardize procedures for effective rhytidectomy. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these evidence-based medicine ratings, please refer to the table of contents or the online instructions to authors at www.springer.com/00266.

Two-dimensional and three-dimensional Fermi surfaces of superconducting BaFe2(As(1-x)P(x))2 and their nesting properties revealed by angle-resolved photoemission spectroscopy.

We have studied the three-dimensional shapes of the Fermi surfaces (FSs) of BaFe(2)(As(1-x)P(x))(2) (x=0.38), where superconductivity is induced by isovalent P substitution and by angle-resolved photoemission spectroscopy. Moderately strong electron mass enhancement has been identified for both the electron and hole FSs. Among two observed hole FSs, the nearly two-dimensional one shows good nesting with the outer two-dimensional electron FS, but its orbital character is different from the outer electron FS. The three-dimensional hole FS shows poor nesting with the electron FSs. The present results suggest that the three dimensionality and the difference in the orbital character weaken FS nesting while partial nesting among the outer electron FSs of d(xy) character and/or that within the three-dimensional hole FS becomes dominant, which may lead to the nodal superconductivity.

Controlling unconventional superconductivity in artificially engineeredf-electron Kondo superlattices.

Unconventional superconductivity and magnetism are intertwined on a microscopic level in a wide class of materials, including high-Tccuprates, iron pnictides, and heavy-fermion compounds. Interactions between superconducting electrons and bosonic fluctuations at the interface between adjacent layers in heterostructures provide a new approach to this most fundamental and hotly debated subject. We have been able to use a recent state-of-the-art molecular-beam-epitaxy technique to fabricate superlattices consisting of different heavy-fermion compounds with atomic thickness. These Kondo superlattices provide a unique opportunity to study the mutual interaction between unconventional superconductivity and magnetic order through the atomic interface. Here, we design and fabricate hybrid Kondo superlattices consisting of alternating layers of superconducting CeCoIn5withd-wave pairing symmetry and nonmagnetic metal YbCoIn5or antiferromagnetic heavy fermion metals such as CeRhIn5and CeIn3. In these Kondo superlattices, superconducting heavy electrons are confined within the two-dimensional CeCoIn5block layers and interact with neighboring nonmagnetic or magnetic layers through the interface. Superconductivity is strongly influenced by local inversion symmetry breaking at the interface in CeCoIn5/YbCoIn5superlattices. The superconducting and antiferromagnetic states coexist in spatially separated layers in CeCoIn5/CeRhIn5and CeCoIn5/CeIn3superlattices, but their mutual coupling via the interface significantly modifies the superconducting and magnetic properties. The fabrication of a wide variety of hybrid superlattices paves a new way to study the relationship between unconventional superconductivity and magnetism in strongly correlated materials.

Unconventional superconductivity and antiferromagnetic quantum critical behavior in the isovalent-doped BaFe2(As1-xPx)2.

Spin dynamics evolution of BaFe2(As(1-x)Px){2} was probed as a function of P concentration via 31P NMR. Our NMR study reveals that two-dimensional antiferromagnetic (AF) fluctuations are notably enhanced with little change in static susceptibility on approaching the AF phase from the superconducting dome. Moreover, the magnetically ordered temperature θ deduced from the relaxation rate vanishes at optimal doping. These results provide clear-cut evidence for a quantum-critical point, suggesting that the AF fluctuations associated with the quantum-critical point play a central role in the high-T(c) superconductivity.

Quasi-two-dimensional Fermi surfaces and coherent interlayer transport in KFe2As2.

We report the results of the angular-dependent magnetoresistance oscillations (AMROs), which can determine the shape of bulk Fermi surfaces (FSs) in quasi-two-dimensional (Q2D) systems, in a highly hole-doped Fe-based superconductor KFe2As2 with Tc ≈ 3.7 K. From the AMROs, we determined the two Q2D FSs with rounded-square cross sections, correspond to 12% and 17% of the first Brillouin zone. The rounded-squared shape of the FS cross section is also confirmed by the analyses of the interlayer transport under in-plane fields. From the obtained FS shape, we infer the character of the 3d orbitals that contribute to the FSs.

Evolution of the Fermi surface of BaFe2(As1-xPx){2} on entering the superconducting dome.

Using the de Haas-van Alphen effect we have measured the evolution of the Fermi surface of BaFe2(As1-xPx){2} as a function of isoelectric substitution (As/P) for 0.41