arXiv subjects

Sethulakshmi Sajeev

Publications and source records attributed to Sethulakshmi Sajeev.

3 recordsLinked to original sources

arXiv2026

Electronic Structure of Epitaxial Films of the Bilayer Strontium Ruthenate: Sr$_{3}$Ru$_2$O$_{7}$

We report a combined study of the low-energy electronic band structure of epitaxial Sr$_3$Ru$_2$O$_7$ films using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT). To investigate the effects of substrate dependence on the band structure, Sr$_3$Ru$_2$O$_7$ thin films are epitaxially grown on SrTiO$_3$ (STO) and (LaAlO$_{3}$)$_{0.3}$(Sr$_{2}$TaAlO$_{6}$)$_{0.7}$ (LSAT) substrates using molecular beam epitaxy. The measured and calculated Fermi-surfaces clearly show substantial changes in the Fermi surface topologies that originate from the underlying strain states. The compressively strained film grown on LSAT exhibits Fermi-surface features consistent with an orthorhombic-like symmetry; and the tensile-strained film grown on STO features a tetragonal-like surface symmetry. In addition, the ARPES data for both films indicate weakly dispersive spectral features within $\sim15~\text{meV}$ below the Fermi level. These observations underscore the strong sensitivity of the electronic structure of Sr$_3$Ru$_2$O$_7$ to epitaxial strain and establish a foundation for future efforts to tune correlated phases in this bilayer ruthenate.

cond-mat.str-el↗

arXiv2025

Magnetotransport Properties in Epitaxial Films of Metallic Delafossite PdCoO$_2$: Effects of Thickness and Width Variations in Hall Bar Devices

We report on a combined structural and magnetotransport study of Hall bar devices of various lateral dimensions patterned side-by-side on epitaxial PdCoO$_2$ thin films. We study the effects of both the thickness of the PdCoO$_2$ film and the width of the channel on the electronic transport and the magnetoresistance properties of the Hall bar devices. All the films with thicknesses down to 4.88 nm are epitaxially oriented, phase pure, and exhibit a metallic behavior. At room temperature, the Hall bar device with the channel width $\text{W}=2.5\, μ\text{m}$ exhibits a record resistivity value of $0.85\,μΩ$cm, while the value of $2.70\,μΩ$cm is obtained in a wider device with channel width $\text{W}=10\, μ\text{m}$. For the 4.88 nm thick sample, we find that while the density of the conduction electrons is comparable in both channels, the electrons move about twice as fast in the narrower channel. At low temperatures, for Hall bar devices of channel width $2.5\,μ\text{m}$ fabricated on epitaxial films of thicknesses 4.88 and 5.21 nm, the electron mobilities of $\approx$ 65 and 40 cm$^2$V$^{-1}$s$^{-1}$, respectively, are extracted. For thin-film Hall bar devices of width $10\,μ\text{m}$ fabricated on the same 4.88 and 5.21 nm thick samples, the mobility values of $\approx$ 32 and 18 cm$^2$V$^{-1}$s$^{-1}$ are obtained. The magnetoresistance characteristics of these PdCoO$_2$ films are observed to be temperature dependent and exhibit a dependency with the orientation of the applied magnetic field. When the applied field is oriented 90° away from the crystal $c$-axis, a persistent negative MR at all temperatures is observed; whereas when the field is parallel to the $c$-axis, the negative magnetoresistance is suppressed at temperatures above 150K.

cond-mat.mtrl-sci↗

arXiv2024

Magnetotransport Properties of Epitaxial Films and Hall Bar Devices of the Correlated Layered Ruthenate Sr$_3$Ru$_2$O$_7$

For epitaxial Sr$_3$Ru$_2$O$_7$ films grown by pulsed laser deposition, we report a combined structural and magnetotransport study of thin films and Hall bar devices patterned side-by-side on the same film. Structural properties of these films are investigated using X-ray diffraction and high-resolution transmission electron microscopy, and confirm that these films are epitaxially oriented and nearly phase pure. For magnetic fields applied along the $c-$axis, a positive magnetoresistance of 10\% is measured for unpatterned Sr$_3$Ru$_2$O$_7$ films, whereas for patterned Hall bar devices of channel widths of $10$ and $5\, μ$m, magnetoresistance values of 40\% and 140\% are found, respectively. These films show switching behaviors from positive to negative magnetoresistance that are controlled by the direction of the applied magnetic field. The present results provide a promising route for achieving stable epitaxial synthesis of intermediate members of correlated layered strontium ruthenates, and for the exploration of device physics in thin films of these compounds.

physics.app-ph↗