arXiv subjects

Jemin Park

Publications and source records attributed to Jemin Park.

5 recordsLinked to original sources

arXiv2025

All-to-All interactions via multifractal wavefunction geometry

We uncover a generic mechanism through which the intrinsic geometry of multifractal quantum wavefunctions generates effective all-to-all interactions in many-body systems. By analyzing the multifractal spectrum, we demonstrate that the simultaneous participation of widely separated length scales creates a global connectivity that bypasses local interaction constraints. This nonlocality leads to fast information scrambling, evidenced by sharp changes in the quenched dynamics of the quantum Fisher information and bipartite mutual information with the onset of negative tripartite mutual information. Such rapid scrambling is a defining feature of strongly chaotic quantum dynamics, and our results identify the systems with multifractal states as a promising solid-state platform for realizing this regime. More broadly, they reveal a new paradigm in which complex, multiscale wavefunction structure intrinsically generates long-range connectivity, providing a natural route to achieving nonlocal behavior in strongly correlated quantum materials.

cond-mat.str-el↗

arXiv2025

Spatial correlations of charge density wave order across the transition in 2H-NbSe2

Charge density waves (CDWs) involve coupled amplitude and phase degrees of freedom, but direct access to local amplitude correlations remains experimentally challenging. Here, we report cryogenic four-dimensional scanning transmission electron microscopy (4D-STEM) measurements of CDW ordering in a 2H-NbSe2 flake of 24 nm thickness, enabled by liquid helium-based cooling. By mapping the spatial distribution of CDW superlattice intensities at nanometer-scale resolution and analyzing their autocorrelations, we extract the temperature-dependent correlation length associated with the local amplitude of the CDW order parameter, independent of global phase coherence. Our results reveal that a finite local CDW amplitude is already established well above the transition temperature. When the system is cooled below the transition temperature down to 20 K, the correlation length extends to nearly 110 nm, and the local CDW amplitude is found to strongly anticorrelate with the local strain field.

cond-mat.str-el↗

arXiv2025

Reallocation of Nonlocal Entanglement in Incommensurate Cold Atom Arrays

Cold atom arrays in optical lattices offer a highly tunable platform for exploring complex quantum phenomena that are difficult to realize in conventional materials. Here, we investigate the emergence of controllable long-range quantum correlations in a simulated twisted bilayer structure with fermionic cold atoms. By exploiting the incommensurate nature of the twisted bilayer, we observe a significant enhancement of long-range susceptibility, suggesting the formation of stable entangled states between spatially distant localized spins. We further show that the tunability of the interlayer coupling in terms of driving fields enables us to manipulate these entangled states without deformation of lattice structure and extra doping. Our findings provide a pathway for overcoming challenges in establishing strong correlations across distant sites, highlighting the potential of optical lattices as a versatile platform for advanced quantum technologies.

cond-mat.quant-gas↗

arXiv2024

Align-to-Distill: Trainable Attention Alignment for Knowledge Distillation in Neural Machine Translation

The advent of scalable deep models and large datasets has improved the performance of Neural Machine Translation. Knowledge Distillation (KD) enhances efficiency by transferring knowledge from a teacher model to a more compact student model. However, KD approaches to Transformer architecture often rely on heuristics, particularly when deciding which teacher layers to distill from. In this paper, we introduce the 'Align-to-Distill' (A2D) strategy, designed to address the feature mapping problem by adaptively aligning student attention heads with their teacher counterparts during training. The Attention Alignment Module in A2D performs a dense head-by-head comparison between student and teacher attention heads across layers, turning the combinatorial mapping heuristics into a learning problem. Our experiments show the efficacy of A2D, demonstrating gains of up to +3.61 and +0.63 BLEU points for WMT-2022 De->Dsb and WMT-2014 En->De, respectively, compared to Transformer baselines.

cs.CL↗

arXiv2024

Controllable Skyrmion Islands in a Moiré Magnet

Antiferromagnetic(AFM) skyrmions have been in the spotlight as ideal topological magnetic bits. Although they are topologically protected, they do not exhibit the skyrmion Hall effect unlike the ferromagnetic ones. Thus, AFM skyrmions are considered to provide a better control of the skyrmion's motion due to the absence of the skyrmion Magnus effect. In this work, we propose a possible realization of controllable AFM skyrmions in a twisted Moiré magnet. The tunability of Moiré materials is not only a good platform for the provision of rich phases, but also for the stabilization of skyrmion phase. We investigate the ground state of twisted bilayer AFM system by solving the Landau-Lifshitz-Gilbert equation in a continuum model. We show that the AFM skyrmions are stabilized even in the absence of the external/dipolar magnetic field, as a consequence of the interplay of interlayer coupling, Dzyaloshinskii-Moriya (DM) interaction and Ising anisotropy. More interestingly, due to the magnetoelectric effect, the application of an external electric field locally stabilizes the skyrmions in the twisted bilayer AFM systems, even in the absence of DM interaction. It also allows the skyrmion helicity to change continuously when both the DM interaction and an electric field are present. We show the phase diagram with respect to the strength of interlayer coupling, the DM interaction and an electric field. Our results suggest the possibility of using AFM skyrmions as stable, controllable topological magnetic bits.

cond-mat.mes-hall↗