arXiv subjects

D. Rout

Publications and source records attributed to D. Rout.

5 recordsLinked to original sources

arXiv2025

High-pressure floating zone crystal growth of Sr$_2$IrO$_4$

Here we demonstrate the floating zone crystal growth of the $J_\mathrm{eff}=1/2$ Mott insulator Sr$_2$IrO$_4$. Historically, the growth of iridates from a ternary melt has been precluded by the extreme vapor pressure of the metal oxide species and the difficulty of maintaining the correct oxidation state of Ir at high temperatures. Here, we show that the application of a high-pressure oxygen growth environment stabilizes the Sr$_2$IrO$_4$ phase, leading to the first demonstration of cm$^{3}$-scale crystals. In contrast to the conventional SrCl$_2$ flux growth method, where poor control over disorder leads to strong sample dependence, the high-pressure floating zone growth enables active control over the homogeneity of the melt. Crystals grown via this technique possess qualitatively similar properties to those grown via flux, with a relatively sharp onset of antiferromagnetic order observed in temperature-dependent magnetization. Further, we demonstrate that by tuning the mixing rate of the melt, we are able to grow natively hole-doped Sr$_2$Ir$_{1-y}$O$_4$, which exhibits a strongly modified magnetic and electronic response.

cond-mat.str-el↗

arXiv2025

Interleaved bond frustration in a triangular lattice antiferromagnet

Frustration of long-range order via lattice geometries serves to amplify fluctuations of the order parameter and generate unconventional ground states that are highly sensitive to perturbations. Traditionally, this concept of geometric frustration is used to engineer unconventional magnetic states in a variety of materials; however, the charge degree of freedom and bond order can be similarly frustrated. Finding materials that host both frustrated magnetic and bond networks holds promise for engineering structural and magnetic states with the potential of coupling to one another via either the magnetic sector (via magnetic field) or via the lattice sector (via strain). In this paper, we identify an unusual instance of this coexistence in the triangular lattice antiferromagnetic compounds $Ln$Cd$_3$P$_3$ ($Ln$ = La, Ce, Pr, and Nd). These compounds feature two-dimensional planes of unique trigonal-planar CdP$_3$ units that manifest an underlying bond instability with its long-range ordering frustrated via emergent kagome ice bond correlations. Our results establish $Ln$Cd$_3$P$_3$ as a rare class of materials where frustrated magnetism across a tunable rare-earth triangular network is embedded within a dopable semiconductor with a frustrated bond order instability.

cond-mat.str-el↗

arXiv2024

Impact of solar wind disappearance event on the Martian nightside ionospheric species: First results

The impact of a rarest solar wind phenomenon [disappearing solar wind (DSW) event during 26-28 December 2022] on the Martian nightside ionosphere is investigated, for the first time, using MAVEN datasets. During an extremely low solar wind density, the Martian top nightside ionospheric species underwent significant enhancements. At a given altitude, the density of electron increased by ~2.5 times, while for ions (NO+, O2+, CO2+, C+, N+, O+, and OH+), it increased by >10 times, respectively, compared to their typical average quiet-time periods. The extremely low dynamic pressure during the DSW event, contrasting with relatively higher nightside ionospheric thermal pressure nearly by an order, suggests an upward ionospheric expansion as a direct consequence. This causes an increased topside ionospheric density. Additionally, the day-to-night plasma transport may also be a contributing factor to increased plasma density. Thus, this study presents a new insight about planetary atmosphere/ionosphere response to the rarest event.

physics.space-ph↗

arXiv2024

Investigation on the impact of solar flares on the Martian atmospheric emissions in the dayside near-terminator region: Case Studies

Solar transient events like flares can cause sudden changes in planetary plasma and neutral environment. Here, we present an investigation of the variability of the Martian atmospheric emissions viz. OI 130.4 nm, 135.6 nm, CO2+ ultraviolet doublet (UVD), and CO Cameron band (CB) in the less explored dayside near-terminator region during solar flare events. The two X8.2 and M6 class flares during September 2017 on Mars have been selected from existing catalogs. Using data from the imaging ultraviolet spectrograph (IUVS) aboard the MAVEN spacecraft, we examined limb radiance profiles. We observed a significant increase in radiance for major emissions around the peak with a more pronounced impact below the peak during flares compared to quiet time. During solar flares, for 130.4 nm and 135.6 nm emission, the maximum deviation in radiance beneath peak approaches to ~63% and ~123%, respectively. Whereas, for CO2+ UVD and CO CB, it is ~64% and ~50%, respectively. Additionally, we have presented an average scenario of dayside near-terminator (SZA~70-90{\deg}) and observed a notable trend of higher percentage deviation for atomic emissions compared to molecular emissions during flares. Further, our analysis depicts a higher percentage deviation during X8.2 compared to M6 class flare. This study underscores that during flares, higher photoelectron impact and irradiance flux drive the production processes, leading to enhanced emissions. The case studies emphasize, for the first time, the significant influence of flares on the Martian dayside near-terminator region, advancing our deeper understanding the impact of varying solar flare intensities to the planetary atmosphere.

physics.space-ph↗

arXiv2023

Martian M2 peak behavior in the dayside near-terminator ionosphere during interplanetary coronal mass ejections

The interplanetary coronal mass ejections (ICMEs) can pose significant impacts on the Martian ionosphere, resulting in plasma depletion, variability, and escape to space. However, the connections between the ICMEs and the associated responses of the dayside near-terminator Martian ionospheric primary peak (M2) are not well understood. The present study primarily investigates the behavior of the ionospheric peak density (Nm) and height (hm) during the passage of ICMEs using observations from the Radio Occultation Science Experiment (ROSE) aboard MAVEN spacecraft. We have selected 8 such ICMEs (during 2017-2022) at Mars from the existing catalogs and studied the ROSE electron density profiles during quiet and disturbed time (ICMEs) for identical solar zenith angle range. We observed the elevation of the M2 peak (hm ~4-16 km) during disturbed time (ICMEs) with a decrease in Nm (0.41-2.8*10^10 m-3) in comparison to the quiet time. The present study, for the first time, addressed the influence of ICMEs on the M2 peak parameters (Nm and hm). We have proposed that the development of large vertical pressure gradient and electron temperature enhancement are plausible causes for ionospheric variability. Therefore, the present study provides new insights to understand peak plasma behavior in the dayside near-terminator ionosphere during ICMEs.

physics.space-ph↗