Search for: All records

Chemical sediments from the Early Eocene Green River Formation can be used for assessing hydroclimate and basin evolution during their deposition. The Wilkins Peak Member (WPM) of the Green River Formation contains a relatively continuous record of perennial closed-basin saline lake deposition in the Bridger Basin, southwest Wyoming, from approximately 51.6 to 49.8 Ma. The volumes and paragenesis of authigenic chemical sediments in the WPM are intrinsically related to the chemical evolution of basin brines. The geographic distribution of those chemical sediments across the Bridger Basin relates to the syn- and post-depositional tectonic history of the basin. In this study, we integrated thermodynamic modeling of chemical evolution of lake brines with chemostratigraphic and lithostratigraphic interpretations of the basin-center Solvay S-34-1 core to evaluate physical and chemical changes to and within ancient Lake Gosiute during the Early Eocene. Fine-scale X-ray fluorescence (XRF) scanning along the length of the core provides a high-resolution chemical stratigraphy of the WPM. Thermodynamic modeling of the evaporation of hypothetical inflow waters and lake brines yield predicted sequences of evaporite minerals, allowing estimation of the salinities and evaporated volumes of water required to reach saturation with respect to observed mineral deposits from the basin. The spatial distributions of bedded evaporites allow us to investigate tectonic changes to the basin during and after the deposition of the WPM. Here, we integrate these data to interpret changes in lake-level, salinity, and hydroclimate of ancient Lake Gosiute during the Early Eocene. 

Abstract The microscopic origins of emergent behaviours in condensed matter systems are encoded in their excitations. In ordinary magnetic materials, single spin-flips give rise to collective dipolar magnetic excitations called magnons. Likewise, multiple spin-flips can give rise to multipolar magnetic excitations in magnetic materials with spin S ≥ 1. Unfortunately, since most experimental probes are governed by dipolar selection rules, collective multipolar excitations have generally remained elusive. For instance, only dipolar magnetic excitations have been observed in isotropic S = 1 Haldane spin systems. Here, we unveil a hidden quadrupolar constituent of the spin dynamics in antiferromagnetic S = 1 Haldane chain material Y 2 BaNiO 5 using Ni L 3 -edge resonant inelastic x-ray scattering. Our results demonstrate that pure quadrupolar magnetic excitations can be probed without direct interactions with dipolar excitations or anisotropic perturbations. Originating from on-site double spin-flip processes, the quadrupolar magnetic excitations in Y 2 BaNiO 5 show a remarkable dual nature of collective dispersion. While one component propagates as non-interacting entities, the other behaves as a bound quadrupolar magnetic wave. This result highlights the rich and largely unexplored physics of higher-order magnetic excitations. 

{"Abstract":["Data files for the manuscript "Quadrupolar magnetic excitations in an isotropic spin-1 antiferromagnet".<\/p>\n\nReference: A. Nag, A. Nocera, S. Agrestini, M. Garcia-Fernandez, A. C. Walters, Sang-Wook Cheong, S. Johnston, and Ke-Jin Zhou, "Quadrupolar magnetic excitations in an isotropic spin-1 antiferromagnet". arXiv:2111.03625 (2021).<\/p>\n\nPreprint: arXiv:2111.03625 (2021), URL: https://arxiv.org/abs/2111.03625<\/p>"]} 

We explore the existence of the collective orbital excitations, orbitons, in the canonical orbital system KCuF3 using the Cu L3-edge resonant inelastic x-ray scattering. We show that the nondispersive highenergy peaks result from the Cu2þ dd orbital excitations. These high-energy modes display good agreement with the ab initio quantum chemistry calculation, indicating that the dd excitations are highly localized. At the same time, the low-energy excitations present clear dispersion. They match extremely well with the two-spinon continuum following the comparison with Müller ansatz calculations. The localized dd excitations and the observation of the strongly dispersive magnetic excitations suggest that the orbiton dispersion is below the resolution detection limit. Our results can reconcile with the strong local Jahn-Teller effect in KCuF3, which predominantly drives orbital ordering. 

Charge-density waves (CDWs) are a ubiquitous form of electron density modulation in cuprate superconductors. Unveiling the nature of quasistatic CDWs and their dynamical excitations is crucial for understanding their origin––similar to the study of antiferromagnetism in cuprates. However, dynamical CDW excitations remain largely unexplored due to the limited availability of suitable experimental probes. Here, using resonant inelastic X-ray scattering, we observe dynamical CDW excitations in Bi2Sr2LaCuO6+δ (Bi2201) superconductors through its interference with the lattice. The distinct anomalies of the bond-buckling and the bond-stretching phonons allow us to draw a clear picture of funnel-shaped dynamical CDW excitations in Bi2201. Our results of the interplay between CDWs and the phonon anomalies shed light on the nature of CDWs in cuprates.