arXiv subjects

Anoop Kamalasanan

Publications and source records attributed to Anoop Kamalasanan.

3 recordsLinked to original sources

arXiv2026

Coupling of two individual magnon resonators via a superconducting microwave resonator operating in the strong coupling regime

We demonstrate coherent coupling of ferromagnetic resonance in two individual permalloy stripes via a superconducting coplanar waveguide resonator. The two stripes are placed on top of the resonator with an angle of 50$^{\circ}$ between their respective long axes. This alignment enables us to separately tune their ferromagnetic resonance frequency by exploiting their shape anisotropy by simply rotating the external bias magnetic field in the sample plane. Both individual ferromagnets exhibit strong coupling with the microwave resonator. This method avoids the use of local individual bias coils and facilitates the integration of similar experiments into planar device infrastructures.

cond-mat.mtrl-sci↗

arXiv2026

Strong coupling between quantized magnon modes in a YIG microstucture and microwaves in a superconducting resonator

Strong-coupling experiments based on magnons enable the exploration into on-chip demonstrations involving numerous long-lived excitations. Yttrium iron garnet (YIG) has been considered for decades as a gold standard material for magnonics due to its low-loss magnonic properties. While YIG has successfully demonstrated strong-coupling in macroscopic device geometries, the strong coupling of magnons in truly sub-10 micron YIG structures to date has not yet been realized. This obstacle is due to the difficulty producing large enough effective magnonic mode volume necessary primarily due to thickness limitations of YIG deposition and device fabrication techniques. Here, we demonstrate the use of a microplatelet of YIG, manufactured from a single crystal of YIG via focused ion beam (FIB) techniques, placed on a constricted inductive line of an optimized superconducting lumped element LC resonator to achieve strong coupling between numerous magnon modes and the LC resonator photons. These experimental findings are qualitatively backed by micromagnetic simulations and quantitatively supported by analytical calculations to identify the magnon modes corresponding to the experimentally observed anti-crossings in the microwave transmission signal. Further, we show that these anti-crossings remain even at incredibly low device input powers ($\leq 10$ fW). The fabrication techniques and device geometry enable the deterministic use of numerous confined magnon modes in micron-scale YIG structures for various magnetic field strengths and orientations at substantially reduced device powers. The results here establish a foundational path forward to achieving efficient magnon-based strong-coupling experiments in micron-scale YIG magnetic elements for effective on-chip studies.

cond-mat.mtrl-sci↗

arXiv2023

Transient vortex dynamics and evolution of Bose metal from a 2D superconductor on MoS$_2$

The true character of physical phenomena is thought to be reinforced as the system becomes disorder-free. In contrast, the two-dimensional (2D) superconductor is predicted to turn fragile and resistive away from the limit I -> 0, B -> 0, in the pinning-free regime. It is intriguing to note that the very vortices responsible for achieving superconductivity by pairing, condensation, and, thereby reducing the classical dissipation, render the state resistive driven by quantum fluctuations in the T -> 0. While cleaner systems are being explored for technological improvements, the 2D superconductor turning resistive when influenced by weak electric and magnetic fields has profound consequences for quantum technologies. A metallic ground state in 2D is beyond the consensus of both Bosonic and Fermionic systems, and its origin and nature warrant a comprehensive theoretical understanding supplemented by in-depth experiments. A real-time observation of the influence of vortex dynamics on transport properties so far has been elusive. We explore the nature and fate of a low-viscous, clean, 2D superconducting state formed on an ionic-liquid gated few-layered MoS$_2$ sample. The vortex-core being dissipative, the elastic depinning, intervortex interaction, and the subsequent dynamics of the vortex-lattice cause the system to behave like an overdamped harmonic oscillator, leaving transient signatures in the transport characteristics. The temperature and magnetic field dependence of the transient nature and the noise characteristics of the magnetoresistance confirm that quantum fluctuations are solely responsible for the Bose metal state and the fragility of the superconducting state.

cond-mat.mes-hall↗