arXiv subjects

Jyotirish Das

Publications and source records attributed to Jyotirish Das.

4 recordsLinked to original sources

arXiv2024

Moiré-mediated phases in synthetic Kondo superlattices

Motivated by the recent experiments on van der Waals heterostructures involving metallic and Mott insulating layers, we construct a moiré extension of the Kondo-Heisenberg model and study its phase diagram via Abrikosov fermion mean field theory in one and two dimensions. Our analysis indicates that the stacking dependent Kondo interaction can lead to a variety of new phases. In particular, we show that magnetic order and heavy quasiparticles can nucleate at different regions in the moiré unit cell leading to a macroscopic real space phase separation. We observe that these factors can lead to a metal to Kondo insulator percolation transition in two dimensions. Our results highlight the rich physics that can arise in moiré superlattices that are composed of inherently strongly correlated layers.

cond-mat.str-el↗

arXiv2023

Theory of moiré magnetism in twisted bilayer $α$-RuCl$_3$

Twisted heterostructures of van der Waals materials have received much attention for their many remarkable properties. Here, we present a comprehensive theory of the long-range ordered magnetic phases of twisted bilayer $α$-RuCl$_3$ via a combination of first-principles calculations and atomistic simulations. While a monolayer exhibits zigzag antiferromagnetic order with three possible ordering wave vectors, a rich phase diagram is obtained for moiré superlattices as a function of interlayer exchange and twist angle. For large twist angles, each layer spontaneously picks a single zigzag ordering wave vector, whereas, for small twist angles, the ground state involves a combination of all three wave vectors in a complex hexagonal domain structure. This multi-domain order minimizes the interlayer energy while enduring the energy cost due to the domain wall formation. Our results indicate that magnetic frustration due to stacking-dependent interlayer exchange in moiré superlattices can be used to tune the magnetic ground state and enhance quantum fluctuations in $α$-RuCl$_3$.

cond-mat.mtrl-sci↗

arXiv2023

Revival of antibiskyrmionic magnetic phases in bilayer NiI$_2$

Magnetic skyrmions are topologically protected spin textures with potential applications in memory and logic devices. Skyrmions have been commonly observed in systems with Dzyaloshinskii-Moriya interaction due to broken inversion symmetry. Yet, recent studies suggest that skyrmions can also be stabilized in systems with inversion symmetry such as Ni-based dihalides due to magnetic frustration. In this article, we employ atomistic simulations to investigate chiral magnetic phases in bilayers of NiI$_2$ and NiBr$_2$. We show that the antiferromagnetic interlayer coupling introduces an additional magnetic frustration and gives rise to a variety of novel spin textures with different topological charges. Specifically for NiI$_2$, we observe that the skyrmions with the in-plane component of spins wrapping around twice (biskyrmions) have an enhanced stability compared to the monolayer case. We also study the polarization induced by the non-colinear magnetic order in NiI$_2$ bilayers and show that the polarization of the topologically nontrivial phases is negligible compared to the spiral phases. Thus, we conclude that polarization measurements can be an indirect route for detecting skyrmions in upcoming experiments.

cond-mat.mes-hall↗

arXiv2022

Skyrmion formation in Ni-based Janus dihalide monolayers: Interplay between magnetic frustration and Dzyaloshinskii-Moriya interaction

We present a comprehensive theory of the magnetic phases in monolayer nickel-based Janus dihalides (NiIBr, NiICl, NiBrCl) through a combination of first-principles calculations and atomistic simulations. Phonon band structure calculations and finite temperature molecular dynamics simulations show that Ni-dihalide Janus monolayers are stable. The parameters of the interacting spin Hamiltonian extracted from ab initio calculations show that nickel-dihalide Janus monolayers exhibit varying degrees of magnetic frustration together with a large Dzyaloshinskii-Moriya interaction due to their inherent inversion symmetry breaking. The atomistic simulations reveal a delicate interplay between these two competing magnetic interactions in giving rise to skyrmion formation.

cond-mat.str-el↗