Time-reversal symmetry-breaking charge order in a kagome superconductor.

The kagome lattice1, which is the most prominent structural motif in quantum physics, benefits from inherent non-trivial geometry so that it can host diverse quantum phases, ranging from spin-liquid phases, to topological matter, to intertwined orders2-8 and, most rarely, to unconventional superconductivity6,9. Recently, charge sensitive probes have indicated that the kagome superconductors AV3Sb5 (A = K, Rb, Cs)9-11 exhibit unconventional chiral charge order12-19, which is analogous to the long-sought-after quantum order in the Haldane model20 or Varma model21. However, direct evidence for the time-reversal symmetry breaking of the charge order remains elusive. Here we use muon spin relaxation to probe the kagome charge order and superconductivity in KV3Sb5. We observe a noticeable enhancement of the internal field width sensed by the muon ensemble, which takes place just below the charge ordering temperature and persists into the superconducting state. Notably, the muon spin relaxation rate below the charge ordering temperature is substantially enhanced by applying an external magnetic field. We further show the multigap nature of superconductivity in KV3Sb5 and that the [Formula: see text] ratio (where Tc is the superconducting transition temperature and λab is the magnetic penetration depth in the kagome plane) is comparable to those of unconventional high-temperature superconductors. Our results point to time-reversal symmetry-breaking charge order intertwining with unconventional superconductivity in the correlated kagome lattice.

Designing the stripe-ordered cuprate phase diagram through uniaxial-stress.

The ability to efficiently control charge and spin in the cuprate high-temperature superconductors is crucial for fundamental research and underpins technological development. Here, we explore the tunability of magnetism, superconductivity, and crystal structure in the stripe phase of the cuprate La[Formula: see text]Ba[Formula: see text]CuO[Formula: see text], with [Formula: see text] = 0.115 and 0.135, by employing temperature-dependent (down to 400 mK) muon-spin rotation and AC susceptibility, as well as X-ray scattering experiments under compressive uniaxial stress in the CuO[Formula: see text] plane. A sixfold increase of the three-dimensional (3D) superconducting critical temperature [Formula: see text] and a full recovery of the 3D phase coherence is observed in both samples with the application of extremely low uniaxial stress of [Formula: see text]0.1 GPa. This finding demonstrates the removal of the well-known 1/8-anomaly of cuprates by uniaxial stress. On the other hand, the spin-stripe order temperature as well as the magnetic fraction at 400 mK show only a modest decrease under stress. Moreover, the onset temperatures of 3D superconductivity and spin-stripe order are very similar in the large stress regime. However, strain produces an inhomogeneous suppression of the spin-stripe order at elevated temperatures. Namely, a substantial decrease of the magnetic volume fraction and a full suppression of the low-temperature tetragonal structure is found under stress, which is a necessary condition for the development of the 3D superconducting phase with optimal [Formula: see text]. Our results evidence a remarkable cooperation between the long-range static spin-stripe order and the underlying crystalline order with the three-dimensional fully coherent superconductivity. Overall, these results suggest that the stripe- and the SC order may have a common physical mechanism.

Dominant and sensitive control of oxidative flux by the ATP-ADP carrier in human skeletal muscle mitochondria: Effect of lysine acetylation.

The adenine nucleotide translocase (ANT) of the mitochondrial inner membrane exchanges ADP for ATP. Mitochondria were isolated from human vastus lateralis muscle (n = 9). Carboxyatractyloside titration of O2 consumption rate (Jo) at clamped [ADP] of 21 µM gave ANT abundance of 0.97 ±â€¯0.14 nmol ANT/mg and a flux control coefficient of 82% ±â€¯6%. Flux control fell to 1% ±â€¯1% at saturating (2 mM) [ADP]. The KmADP for Jo was 32.4 ±â€¯1.8 µM. In terms of the free (-3) ADP anion this KmADP was 12.0 ±â€¯0.7 µM. A novel luciferase-based assay for ATP production gave KmADP of 13.1 ±â€¯1.9 µM in the absence of ATP competition. The free anion KmADP in this case was 2.0 ±â€¯0.3 µM. Targeted proteomic analyses showed significant acetylation of ANT Lysine23 and that ANT1 was the most abundant isoform. Acetylation of Lysine23 correlated positively with KmADP, r = 0.74, P = 0.022. The findings underscore the central role played by ANT in the control of oxidative phosphorylation, particularly at the energy phosphate levels associated with low ATP demand. As predicted by molecular dynamic modeling, ANT Lysine23 acetylation decreased the apparent affinity of ADP for ANT binding.

Avoided valence transition in a plutonium superconductor.

The d and f electrons in correlated metals are often neither fully localized around their host nuclei nor fully itinerant. This localized/itinerant duality underlies the correlated electronic states of the high-Tc cuprate superconductors and the heavy-fermion intermetallics and is nowhere more apparent than in the 5f valence electrons of plutonium. Here, we report the full set of symmetry-resolved elastic moduli of PuCoGa5--the highest Tc superconductor of the heavy fermions (Tc = 18.5 K)--and find that the bulk modulus softens anomalously over a wide range in temperature above Tc. The elastic symmetry channel in which this softening occurs is characteristic of a valence instability--therefore, we identify the elastic softening with fluctuations of the plutonium 5f mixed-valence state. These valence fluctuations disappear when the superconducting gap opens at Tc, suggesting that electrons near the Fermi surface play an essential role in the mixed-valence physics of this system and that PuCoGa5 avoids a valence transition by entering the superconducting state. The lack of magnetism in PuCoGa5 has made it difficult to reconcile with most other heavy-fermion superconductors, where superconductivity is generally believed to be mediated by magnetic fluctuations. Our observations suggest that valence fluctuations play a critical role in the unusually high Tc of PuCoGa5.

A multi-component Fermi surface in the vortex state of an underdoped high-Tc superconductor.

To understand the origin of superconductivity, it is crucial to ascertain the nature and origin of the primary carriers available to participate in pairing. Recent quantum oscillation experiments on high-transition-temperature (high-T(c)) copper oxide superconductors have revealed the existence of a Fermi surface akin to that in normal metals, comprising fermionic carriers that undergo orbital quantization. The unexpectedly small size of the observed carrier pocket, however, leaves open a variety of possibilities for the existence or form of any underlying magnetic order, and its relation to d-wave superconductivity. Here we report experiments on quantum oscillations in the magnetization (the de Haas-van Alphen effect) in superconducting YBa(2)Cu(3)O(6.51) that reveal more than one carrier pocket. In particular, we find evidence for the existence of a much larger pocket of heavier mass carriers playing a thermodynamically dominant role in this hole-doped superconductor. Importantly, characteristics of the multiple pockets within this more complete Fermi surface impose constraints on the wavevector of any underlying order and the location of the carriers in momentum space. These constraints enable us to construct a possible density-wave model with spiral or related modulated magnetic order, consistent with experimental observations.

Metal-insulator quantum critical point beneath the high Tc superconducting dome.

An enduring question in correlated systems concerns whether superconductivity is favored at a quantum critical point (QCP) characterized by a divergent quasiparticle effective mass. Despite such a scenario being widely postulated in high T(c) cuprates and invoked to explain non-Fermi liquid transport signatures, experimental evidence is lacking for a critical divergence under the superconducting dome. We use ultrastrong magnetic fields to measure quantum oscillations in underdoped YBa(2)Cu(3)O(6+x), revealing a dramatic doping-dependent upturn in quasiparticle effective mass at a critical metal-insulator transition beneath the superconducting dome. Given the location of this QCP under a plateau in T(c) in addition to a postulated QCP at optimal doping, we discuss the intriguing possibility of two intersecting superconducting subdomes, each centered at a critical Fermi surface instability.

Tunable unconventional kagome superconductivity in charge ordered RbV3Sb5 and KV3Sb5.

Unconventional superconductors often feature competing orders, small superfluid density, and nodal electronic pairing. While unusual superconductivity has been proposed in the kagome metals AV3Sb5, key spectroscopic evidence has remained elusive. Here we utilize pressure-tuned and ultra-low temperature muon spin spectroscopy to uncover the unconventional nature of superconductivity in RbV3Sb5 and KV3Sb5. At ambient pressure, we observed time-reversal symmetry breaking charge order below [Formula: see text] 110 K in RbV3Sb5 with an additional transition at [Formula: see text] 50 K. Remarkably, the superconducting state displays a nodal energy gap and a reduced superfluid density, which can be attributed to the competition with the charge order. Upon applying pressure, the charge-order transitions are suppressed, the superfluid density increases, and the superconducting state progressively evolves from nodal to nodeless. Once optimal superconductivity is achieved, we find a superconducting pairing state that is not only fully gapped, but also spontaneously breaks time-reversal symmetry. Our results point to unprecedented tunable nodal kagome superconductivity competing with time-reversal symmetry-breaking charge order and offer unique insights into the nature of the pairing state.

Quantum oscillations from nodal bilayer magnetic breakdown in the underdoped high temperature superconductor YBa2Cu3O(6+x).

We report quantum oscillations in underdoped YBa2Cu3O6.56 over a significantly large range in magnetic field extending from ≈24 to 101 T, enabling three well-spaced low frequencies at ≈440±10, 532±2, and 620±10 T to be clearly resolved. We show that a small nodal bilayer coupling that splits a nodal pocket into bonding and antibonding orbits yields a sequence of frequencies, F0-ΔF, F0, and F0+ΔF and accompanying beat pattern similar to that observed experimentally, on invoking magnetic breakdown tunneling at the nodes. The relative amplitudes of the multiple frequencies observed experimentally in quantum oscillation measurements are shown to be reproduced using a value of nodal bilayer gap quantitatively consistent with that measured in photoemission experiments in the underdoped regime.

Cascade of magnetic field induced spin transitions in LaCoO3.

We present magnetization and magnetostriction studies of LaCoO3 in magnetic fields approaching 100 T. In contrast with expectations from single-ion models, the data reveal two distinct first-order transitions and well-defined magnetization plateaus. The magnetization at the higher plateau is only about half the saturation value expected for spin-1 Co3+ ions. These findings strongly suggest collective behavior induced by interactions between different electronic configurations of Co3+ ions. We propose a model that predicts crystalline spin textures and a cascade of four magnetic phase transitions at high fields, of which the first two account for the experimental data.

Magnetic quantum oscillations in YBa2Cu3O6.61 and YBa2Cu3O6.69 in fields of up to 85 T: patching the hole in the roof of the superconducting dome.

We measure magnetic quantum oscillations in the underdoped cuprates YBa2Cu3O6+x with x=0.61, 0.69, using fields of up to 85 T. The quantum-oscillation frequencies and effective masses obtained suggest that the Fermi energy in the cuprates has a maximum at hole doping p approximately 0.11-0.12. On either side, the effective mass may diverge, possibly due to phase transitions associated with the T=0 limit of the metal-insulator crossover (low-p side), and the postulated topological transition from small to large Fermi surface close to optimal doping (high p side).

Polycrystalline gamma-plutonium's elastic moduli versus temperature.

Resonant ultrasound spectroscopy was used to measure the elastic properties of pure polycrystalline (239)Pu in the gamma-phase. Shear and longitudinal elastic moduli were measured simultaneously and the bulk modulus was computed from them. A smooth, linear, and large decrease in all elastic moduli with increasing temperature was observed. The Poisson ratio was calculated and an increase from 0.242 at 519 K to 0.252 at 571 K was found. These measurements on extremely well-characterized pure Pu are in agreement with other reported results where overlap occurs. We calculated an approximate Debye temperature Theta(D)=144 K. Determined from the temperature variation in the bulk modulus, gamma-Pu shows the same Gruneisen parameter as copper.

Spin-order driven Fermi surface reconstruction revealed by quantum oscillations in an underdoped high Tc superconductor.

We use quantum oscillation measurements to distinguish between spin and orbital components of the lowest energy quasiparticle excitations in YBa(2)Cu(3)O(6.54), each of which couple differently to a magnetic field. Our measurements reveal the phase of the observed quantum oscillations to remain uninverted over a wide angular range, indicating that the twofold spin degeneracy of the Landau levels is virtually unaltered by the magnetic field. The inferred suppression of the spin degrees of freedom indicates a spin-density wave is responsible for creation of the small Fermi surface pockets in underdoped YBa(2)Cu(3)O(6+x)--further suggesting that excitations of this phase are important contributors to the unconventional superconducting pairing mechanism.

Biological significance of unwinding capability of nuclear matrix-associating DNAs.

Matrix attachment regions (MARs) are thought to separate chromatin into topologically constrained loop domains. A MAR located 5' of the human beta-interferon gene becomes stably base-unpaired under superhelical strain, as do the MARs flanking the immunoglobulin heavy chain gene enhancer; in both cases a nucleation site exists for DNA unwinding. Concatemerized oligonucleotides containing the unwinding nucleation site exhibited a strong affinity for the nuclear scaffold and augmented SV40 promoter activity in stable transformants. Mutated concatemerized oligonucleotides resisted unwinding, showed weak affinity for the nuclear scaffold, and did not enhance promoter activity. These results suggest that the DNA feature capable of relieving superhelical strain is important for MAR functions.

Fermi surface of CeIn3 above the Néel critical field.

We report measurements of the de Haas-van Alphen effect in CeIn(3) in magnetic fields extending to approximately 90 T, well above the Néel critical field of mu(0)H(c) approximately 61 T. The unreconstructed Fermi surface a sheet is observed in the high magnetic field polarized paramagnetic limit, but with its effective mass and Fermi surface volume strongly reduced in size compared to that observed in the low magnetic field paramagnetic regime under pressure. The spheroidal topology of this sheet provides an ideal realization of the transformation from a "large Fermi surface" accommodating f electrons to a "small Fermi surface" when the f-electron moments become polarized.

Alpha-plutonium's polycrystalline elastic moduli over its full temperature range.

alpha-plutonium's volume-corrected polycrystal elastic moduli were measured between 18 K and the upper limit of its occurrence, near 400 K. The two independent moduli for a polycrystal-bulk and shear-behave smoothly, indicating no phase transition. Both moduli show the same 50% increase on cooling, an order of magnitude larger than in other metals. The Debye temperature obtained from low-temperature elastic moduli, 207 K, significantly exceeds most previous estimates. The Gruneisen parameter gamma=5.3, obtained from the temperature dependence of the bulk modulus, is intermediate among previous estimates using other approaches, alpha-plutonium's Poisson ratio nu is low: 0.18, nearly temperature independent, and its small decrease on warming opposes usual behavior. The high gamma, large but equal bulk modulus and shear modulus fractional stiffening on cooling, and near-temperature-invariant nu are attributed to a single mechanism: 5-f electron localization-delocalization.

Deep sclerectomy and low dose mitomycin C: a randomised prospective trial in west Africa.

AIM: To study the efficacy and safety of deep sclerectomy (DS) augmented with intraoperative low dose mitomycin C (MMC) in a west African population. METHODS: Prospective, randomised, controlled trial. Trial participants were Nigerian patients with medically uncontrolled primary open angle glaucoma undergoing primary surgery at Maja Hospital, Lagos, Nigeria. 39 eyes of 39 patients undergoing DS were randomised into receiving intraoperative MMC 0.25 mg/ml for 2 minutes at the end of procedure (DS-MMC) and a control group (DS-noMMC). RESULTS: There were 21 patients in the DS-noMMC and 18 in the DS-MMC group with no difference in the preoperative characteristics of the groups. Mean follow up was 16.4 (SD 11.3) months. The probability of maintaining an intraocular pressure less than 18 mm Hg with or without additional medications (95% confidence intervals) at 1 year was 70% (47-92%, 95%) and 79% (57-100%), and at 18 months was 35% (8-62%) and 38% (7-69%) for the DS-noMMC and DS-MMC groups, respectively, with no difference in success rates (p = 0.6). An IOP of less than 18 mm Hg without additional medication was maintained in 65% (41-89%) and 73% (49-96%) at 1 year and 24% (8-48%) and 13% (13-46%) at 18 months for the DS-noMMC and DS-MMC groups, respectively (p = 0.5). There were no serious complications related to the procedure. CONCLUSIONS: The success rates of DS in black west African glaucoma patients, as performed in this study, were low. The study did not achieve sufficient power to detect whether low dose intraoperative MMC application can increase success rates of DS.

Scaffold/matrix-attached regions: structural properties creating transcriptionally active loci.

The expression characteristics of the human interferon-beta gene, as part of a long stretch of genomic DNA, led to the discovery of the putative domain bordering elements. The chromatin structure of these elements and their surroundings was determined during the process of gene activation and correlated with their postulated functions. It is shown that these "scaffold-attached regions" (S/MAR elements) have some characteristics in common with and others distinct from enhancers with which they cooperate in various ways. Our model of S/MAR function will focus on their properties of mediating topological changes within the respective domain.

Comparative effects of aspirin and acetaminophen on hemostasis.

The influences of aspirin and of acetaminophen on hemostasis were studied in normal healthy volunteers and in patients with either severe hemophilia A or hemophilia B. Acetaminophen did not alter the template bleeding time or the results of tests of platelet function in either group. Aspirin did prolong the template bleeding time and impaired platelet aggregation; these changes were most pronounced in patients with either form of hemophilia, and some (7/19) required plasma component therapy. Neither drug influenced the coagulation proteins or the fibrinolytic mechanism, as measured. The influences of a single dose (ranging from 975 to 1,950 mg) of acetaminophen and of a single dose (ranging from 325 to 2,925 mg) of aspirin were similar to those observed in persons receiving multiple doses. Acetaminophen is preferred in patients in whom a hemostatic influence is undesirable. However, either aspirin or acetaminophen can be used in normal healthy subjects.

Colchicine toxicity: a multisystem disease.

A 23-year-old black man survived a life-threatening multisystem disturbance resulting from a large single dose of colchicine administered intraurethrally for condyloma acuminata. Gastroenteritis and probable pancreatitis rapidly evolved into severe respiratory failure, marked neuromuscular problems, alopecia, and complete bone marrow aplasia. Within two months he had completely recovered. This patient demonstrates that colchicine should be used with extreme caution, if at all, for the therapy of condyloma acuminata.

Therapeutic leukapheresis in hairy cell leukemia.

Therapeutic leukapheresis was performed on three patients, and plasmapheresis on two patients with far-advanced hairy cell leukemia. Two of the three patients who were treated with leukapheresis had many hairy cells in their peripheral blood, while the other had relatively few. In each patient, dramatic clinical and hematologic improvements were observed that have sustained for more than 23, 10, and 26 months, respectively. Plasmapheresis of similar intensity failed to show any appreciable therapeutic effects on two other patients with similar clinical and hematologic findings. We believe that the favorable therapeutic effects of leukapheresis are due to the removal of factors capable of inhibiting normal hematopoiesis. This factor(s) is present in the cells that were removed by leukapheresis. The exact nature of this factor(s) or the cells that produce this factor(s) remains to be identified.