arXiv subjects

G. Senthil Murugan

Publications and source records attributed to G. Senthil Murugan.

4 recordsLinked to original sources

arXiv2026

Multistage spin correlations in the $s$ = 1/2 stuffed hyper-star lattice Li$_{2}$Cu$_{2}$(MoO$_{4}$)$_{3}$

Star lattice, which can be visualized as a honeycomb network with each vertex replaced by a triangle, provides a rare platform for realizing exotic quantum states such as quantum spin liquids and disorder-driven random-singlet (RS) states. Herein, we investigate the ground-state properties of the three-dimensional (3D) stuffed hyper-star lattice Li$_2$Cu$_2$(MoO$_4$)$_3$, which exhibits a crossover from short-range spin correlations to a disorder-driven RS-like state below $T^{*}\sim$15.8 K. Thermodynamic and microscopic measurements capture this crossover through a change in the power-law behavior of various observables, from $\sim T^{0.25}$ for $T > T^{*}$ to $\sim T^{-0.50}$ for $T < T^{*}$. Upon further cooling, a quasi-frozen state emerges near $T_{\rm f} = 0.32$ K, likely associated with weakly coupled spin chains within the hyper-star spin network. Our results underscore the crucial role of orphan spins and weak residual interactions in stabilizing a disorder-driven quantum-disordered state in 3D.

cond-mat.str-el↗

arXiv2025

Possible Bose-Einstein condensation of magnons in a S = 5/2 honeycomb lattice

Quantum magnets offer a unique platform for exploring exotic quantum phases and quantum phase transitions through external magnetic fields. A prominent example is the field-induced Bose--Einstein condensation (BEC) of magnons near the saturation field. While this behavior has been observed in low-spin systems, its realization in high-spin, quasi-two-dimensional magnets -- where multiple on-site excitations are possible -- remains exceptionally rare. Here, we report thermodynamic and density functional theory results on single crystals of the honeycomb-lattice antiferromagnet K$_{4}$MnMo$_{4}$O$_{15}$ with $S = 5/2$. The system undergoes a field-induced transition to a fully polarized state at the critical field $μ_{0}H_{\rm s} = 6.4$~T. Our results reveal possible thermodynamic signatures of magnon BEC, $T_{\mathrm{N}} \sim (H_{\rm s} - H)^{2/d}$ ($d = 3$), expanding the purview of BEC-driven quantum criticality to a high-spin, quasi-two-dimensional antiferromagnets with negligibly small anisotropy.

cond-mat.str-el↗

arXiv2025

Spin dynamics and 1/3 magnetization plateau in a coupled distorted diamond chain compound K2Cu3(MoO4)4

We investigate magnetic properties of the $s$ = 1/2 compound K$_{2}$Cu$_{3}$(MoO$_{4}$)$_{4}$ by combining magnetic susceptibility, magnetization, specific heat, and electron spin resonance (ESR) with density functional calculations. Its monoclinic structure features alternating Cu$^{2+}$ ($s$ = 1/2) monomers and edge-shared dimers linked by MoO$_{4}$ units, forming a distorted diamond chain along the $a$-axis. Antiferromagnetic order occurs at $T_{\rm N}$ = 2.3 K, as evident from a $λ$-type anomaly in specific heat and magnetic susceptibility derivatives. Inverse magnetic susceptibility reveals coexisting ferro- and antiferromagnetic interactions. Specific heat and ESR data show two characteristic temperatures: one at 20 K, associated with spin-singlet formation in Cu$_{2}$O$_{9}$ dimers, and another at 3.68 K, indicating short-range correlations between dimers and monomers. Magnetization measurements reveal a metamagnetic transition at 2.6 T and a critical magnetic field $μ_{0}H_{c}$ = 3.4 T, where a 1/3 magnetization plateau emerges with saturation near 0.35 $μ_{\rm B}$. Low-temperature specific heat and magnetization data reveal the suppression of long-range order at $μ_{0}H_{c}$, enabling the construction of a temperature-magnetic field phase diagram showing multiple magnetic phases near the $μ_{0}H_{c}$. Density functional theory confirms a distorted diamond chain with $J_{1}$ dimers and competing $J_2$, $J_4$, $J_3$, and $J_5$ interactions with monomer spins as an effective low-temperature spin model.

cond-mat.str-el↗

arXiv2018

Chip-based Resonance Raman Spectroscopy Using Tantalum Pentoxide Waveguides

Blood analysis is an important diagnostic tool, as it provides a wealth of information about the patient health. Raman spectroscopy is a promising tool in blood analysis, but widespread clinical application is limited by its low signal strength, as well as complex and costly instrumentation. The growing field of waveguide-based Raman spectroscopy tries to solve these challenges by working towards fully integrated Raman sensors with increased interaction areas. In this work, we demonstrate on-chip resonance Raman measurements of hemoglobin, a crucial component of blood, at 532 nm excitation using a tantalum pentoxide (Ta2O5) waveguide platform. We have also characterized the background signal from Ta2O5 waveguide material when excited at 532 nm. In addition, we demonstrate spontaneous Raman measurements of iso-propanol and methanol using the same platform. Our results suggest that Ta2O5 is a promising waveguide platform for resonance Raman spectroscopy at 532 nm, and in particular for blood analysis.

physics.app-ph↗