Quasi-1D dynamics and nematic phases in the 2D Emery model

We consider the Emery model of a Cu-O plane of the high temperature superconductors. We show that in a strong-coupling limit, with strong Coulomb repulsions between electrons on nearest-neighbor O sites, the electron-dynamics is strictly one dimensional, and consequently a number of asymptotically exact results can be obtained concerning the electronic structure. In particular, we show that a nematic phase, which spontaneously breaks the point- group symmetry of the square lattice, is stable at low enough temperatures and strong enough coupling.Comment: 8 pages, 5 eps figures; revised manuscript with more detailed discussions; two new figures and three edited figuresedited figures; 14 references; new appendix with a detailed proof of the one-dimensional dynamics of the system in the strong coupling limi

Electronic Liquid Crystal Phases of a Doped Mott Insulator

The character of the ground state of an antiferromagnetic insulator is fundamentally altered upon addition of even a small amount of charge. The added charges agglomerate along domain walls at which the spin correlations, which may or may not remain long-ranged, suffer a $\pi$ phase shift. In two dimensions, these domain walls are ``stripes'' which are either insulating, or conducting, i.e. metallic rivers with their own low energy degrees of freedom. However, quasi one-dimensional metals typically undergo a transition to an insulating ordered charge density wave (CDW) state at low temperatures. Here it is shown that such a transition is eliminated if the zero-point energy of transverse stripe fluctuations is sufficiently large in comparison to the CDW coupling between stripes. As a consequence, there exist novel, liquid-crystalline low-temperature phases -- an electron smectic, with crystalline order in one direction, but liquid-like correlations in the other, and an electron nematic with orientational order but no long-range positional order. These phases, which constitute new states of matter, can be either high temperature supeconductors or two-dimensional anisotropic ``metallic'' non-Fermi liquids. Evidence for the new phases may already have been obtained by neutron scattering experiments in the cuprate superconductor, La_{1.6-x}Nd_{0.4}Sr_xCuO_{4}.Comment: 5 pages in RevTex with two figures in ep

Left High and Dry: Deglaciation of Dogger Bank, North Sea, Recorded in Proglacial Lake Evolution

Reconstructions of palaeo-ice sheet retreat in response to climate warming using offshore archives can provide vital analogs for future ice-sheet behavior. At the Last Glacial Maximum, Dogger Bank, in the southern North Sea, was covered by the Eurasian Ice Sheet. However, the maximum extent and behavior of the ice sheet in the North Sea basin is poorly constrained. We reveal ice-marginal dynamics and maximum ice extent at Dogger Bank through sedimentological and stratigraphic investigation of glacial and proglacial lake sediments. We use a large, integrated subsurface dataset of shallow seismic reflection and geotechnical data collected during windfarm site investigation. For the first time, an ice stream is identified at Dogger Bank, based on preserved subglacial bedforms, eskers and meltwater channels. During ice-sheet advance, a terminal thrust-block moraine complex formed, whose crest runs approximately north-northeast to south-southwest. Subsequent ice stream shutdown caused stagnation of ice, and rapid retreat of the ice-sheet margin. The moraine complex, and outwash head from an adjacent ice-sheet lobe to the west, dammed a large (approximately 750 km2) proglacial lake. Subsequent sedimentation infilled the lake with 30 m of glacial outwash sediments. A lobate subaqueous fan formed at the ice-sheet margin, which thins toward the southeast with iceberg scours and ice-rafted debris at the base, and is onlapped by lake sediments calibrated to core as alternating clay and silt laminae, interpreted to be varves. The lake became isolated from the retreating ice-sheet margin, and ice-sheet retreat slowed. Sediment-laden meltwater was supplied to the ice-distal proglacial lake for c. 1500–2000 years. Subsequent ice-sheet retreat off Dogger Bank was more rapid due to the negative subglacial slope. The stepped retreat of rapid downwasting, slow retreat, and a final rapid phase off Dogger Bank occurred after the LGM at around 27 ka and before formation of a ribbon lake, dated previously to 23 ka and approximately 60 m lower in elevation, formed to the north of Dogger Bank. The complicated stratigraphic architecture revealed through these data improves forecasting of ground conditions for turbine footings at Dogger Bank, an important step in the provision of clean, sustainable energy

Topographic and hydrodynamic controls on barrier retreat and preservation: An example from Dogger Bank, North Sea

Barrier retreat can occur due to in-place drowning, overstepping or rollover, depending on the interplay of controls such as sea-level rise, sediment supply, coastal hydrodynamic regime and topography. Offshore sedimentary archives of barriers active during rapid Holocene sea-level rise provide important records of marine transgression, which are vital analogues to support appropriate mitigation strategies for future coastal realignment under projected relative sea-level rise scenarios. This study analyses the sedimentary archive at Dogger Bank, which is a formerly-glaciated area in the North Sea. Dogger Bank experienced marine transgression due to Early Holocene rapid relative sea-level rise. An integrated dataset of vibrocores and high-resolution seismic reflection data permits a stratigraphic framework to be established, which reveals the buried coastal geomorphology of the southern Dogger Bank for the first time. A transgressive stratigraphy was identified, comprising a topographically complicated basal glacial and terrestrial succession, overlain by two phases of barrier and tidal mudflat deposition, prior to shallow marine sedimentation. Barrier phase A was a recurved barrier drowned in place, and discontinuously overstepped to barrier phase B, which experienced continuous overstepping. By linking barrier elevations to relative sea-level curves, the timing of each barrier phase was established. Both barrier phases retreated during periods of rapid sea-level rise with abundant sediment supply. Coastal hydrodynamics (increasing wave energy) and antecedent topography with spatially variable accommodation are suggested to be the main reason for differing retreat mechanisms, rather than the rate of sea-level rise. Antecedent coastal geomorphology plays a critical role in erosional and depositional patterns during transgression, and therefore on the timing, rate and location of marine inundation, which needs to be included in models that aim to forecast hazards in coastal areas

Local versus Nonlocal Order Parameter Field Theories for Quantum Phase Transitions

General conditions are formulated that allow to determine which quantum phase transitions in itinerant electron systems can be described by a local Landau-Ginzburg-Wilson or LGW theory solely in terms of the order parameter. A crucial question is the degree to which the order parameter fluctuations couple to other soft modes. Three general classes of zero-wavenumber order parameters, in the particle-hole spin-singlet and spin-triplet channels, and in the particle-particle channel, respectively, are considered. It is shown that the particle-hole spin-singlet class does allow for a local LGW theory, while the other two classes do not. The implications of this result for the critical behavior at various quantum phase transitions are discussed, as is the connection with nonanalyticities in the wavenumber dependence of order parameter susceptibilities in the disordered phase.Comment: 9 pp., LaTeX, no figs, final version as publishe

Discrimination between the superconducting gap and the pseudo-gap in Bi2212 from intrinsic tunneling spectroscopy in magnetic field

Intrinsic tunneling spectroscopy in high magnetic field ($H$) is used for a direct test of superconducting features in a quasiparticle density of states of high-$T_c$ superconductors. We were able to distinguish with a great clarity two co-existing gaps: (i) the superconducting gap, which closes as $H \to H_{c2}(T)$ and $T\to T_c(H)$, and (ii) the $c$-axis pseudo-gap, which does not change neither with $H$, nor $T$. Strikingly different magnetic field dependencies, together with previously observed different temperature dependencies of the two gaps ~\cite{Krasnov}, speak against the superconducting origin of the pseudo-gap.Comment: 4 pages, 4 eps figure

Ice sheet and palaeoclimate controls on drainage network evolution: an example from Dogger Bank, North Sea

Submerged landscapes on continental shelves archive drainage networks formed during periods of sea-level lowstand. The evolution of these postglacial drainage networks also reveals how past climate changes affected the landscape. Ice-marginal and paraglacial drainage networks on low-relief topography are susceptible to reorganisation of water supply, forced by ice-marginal rearrangement, precipitation and temperature variations, and marine inundation. A rare geological archive of climate-driven landscape evolution during the transition from ice-marginal (ca. 23 ka) to a fully submerged marine environment (ca. 8 ka) is preserved at Dogger Bank, in the southern North Sea. In this study, our analysis of high-resolution seismic reflection and cone penetration test data reveal a channel network over a 1330 km2 area that incised glacial and proglacial lake-fill sediments. The channel network sits below coastal and shallow marine sediments and is therefore interpreted to represent a terrestrial drainage network. When mapped out, the channel form morphology reveals two distinct sets. The first set comprises two low-sinuosity, wide (>400 m) channels that contain macroforms of braid and side bars. These channels are interpreted to have originated as proglacial rivers, which drained the ice-sheet margin to the north. The second set of channels (75–200 m wide, with one larger, ∼400 m wide) has higher sinuosity and forms a subdendritic network of tributaries to the proglacial channels. The timing of channel formation lacks chronostratigraphic control. However, the proglacial rivers must have formed as the ice sheet was still on Dogger Bank, before 23 ka, to supply meltwater to the rivers. Ice-sheet retreat from Dogger Bank led to reorganisation of meltwater drainage and abandonment of the proglacial rivers. Palaeoclimate simulations show a cold and dry period at Dogger Bank between 23 and 17 ka. After 17 ka, precipitation increased, and drainage of precipitation formed the second set of channels. The second set of rivers remained active until marine transgression of Dogger Bank at ca. 8.5–8 ka. Overall, this study provides a detailed insight into the evolution of river networks across Dogger Bank and highlights the interplay between external (climate) and internal (local) forcings in drainage network evolution

Unilateral anterior uveitis complicating zoledronic acid therapy in breast cancer

BACKGROUND: Zoledronic acid is very widely used in patients with metastatic bone disease and osteoporosis. Only one case of bilateral uveitis was recently reported related to its use. CASE PRESENTATION: We report the first case of severe unilateral anterior uveitis in a patient with breast cancer and an intraocular lens. Following zoledronic acid infusion, the patient developed severe and dramatic right eye pain with decreased visual acuity within 24 hours and was found to have a fibrinous anterior uveitis of moderate severity The patient was treated with topical prednisone and atropine eyedrops and recovered slowly over several months. CONCLUSION: Internists, oncologists, endocrinologists, and ophtalmologists should be aware of uveitis as a possible complication of zoledronic acid therapy. Patients should be instructed to report immediately to their physicians and treatment with topical prednisone and atropine eyedrops should be instituted immediately at the onset of symptoms. This report documents anterior uveitis as a complication of zoledronic acid therapy. This reaction could be an idiosyncratic one but further research may shed more light on the etiology

Dispersive charge density wave excitations and temperature dependent commensuration in Bi2Sr2CaCu2O8+{\delta}

Experimental evidence on high-Tc cuprates reveals ubiquitous charge density wave (CDW) modulations, which coexist with superconductivity. Although the CDW had been predicted by theory, important questions remain about the extent to which the CDW influences lattice and charge degrees of freedom and its characteristics as functions of doping and temperature. These questions are intimately connected to the origin of the CDW and its relation to the mysterious cuprate pseudogap. Here, we use ultrahigh resolution resonant inelastic x-ray scattering (RIXS) to reveal new CDW character in underdoped Bi2Sr2CaCu2O8+{\delta} (Bi2212). At low temperature, we observe dispersive excitations from an incommensurate CDW that induces anomalously enhanced phonon intensity, unseen using other techniques. Near the pseudogap temperature T*, the CDW persists, but the associated excitations significantly weaken and the CDW wavevector shifts, becoming nearly commensurate with a periodicity of four lattice constants. The dispersive CDW excitations, phonon anomaly, and temperature dependent commensuration provide a comprehensive momentum space picture of complex CDW behavior and point to a closer relationship with the pseudogap state