DSC09851-_Christoph_Hohmann_3600px

Distinguished Postdoc 2023

Max Planck Institute of Quantum Optics

Hans-Kopfermann-Str. 1

85748 Garching

mingru.yang(at)mpq.mpg.de

Research Website

The ideas in one field can be used in some other fields such that the encounter inspires new angles and revolutionizes the methodologies.

Description

Research focus: Tensor networks and condensed matter physics

I have been fascinated by the interplay between quantum information and condensed matter physics, particularly, the tensor networks, whose structure naturally captures the internal entanglement feature of various exotic phases. My research aims to not only utilize and develop tensor network methods to perform conventional numerical simulation, but also to provide new perspectives on formulating and understanding problems in quantum many-body physics and quantum field theory from a tensor network point of view.


Further reading

Publications

Beyond fragmented dopant dynamics in quantum spin lattices: Robust localization and non-Gaussian diffusion

M. Yang, S. Anand, K. K. Nielsen

Physical Review B 112 (16), 165129 (2025).

Show Abstract

The motion of dopants in magnetic spin lattices has received tremendous attention for at least four decades due to its connection to high-temperature superconductivity. Despite these efforts, we lack a complete understanding of their behavior, especially out of the equilibrium and at nonzero temperatures. In this paper, we take a significant step towards a much deeper understanding based on state-of-the-art matrix-product-state calculations. In particular, we investigate the nonequilibrium dynamics of a dopant in two-leg t-J ladders with antiferromagnetic XXZ spin interactions. In the Ising limit, we find that the dopant is localized for all investigated nonzero temperatures due to an emergent disordered potential, with a localization length controlled by the underlying correlation length of the spin lattice, which increases exponentially with decreasing temperature. The dopant, hereby, only delocalizes asymptotically in the zero temperature limit. This greatly generalizes the localization effect discovered recently in Hilbert space fragmented models [Phys. Rev. Res. 6, 023325 (2024), SciPost Phys. Core 7, 054 (2024)]. In the presence of spin-exchange processes at rate alpha, the dopant diffuses with a diffusion coefficient, Dh, depending nonmonotonically on alpha. It initially increases linearly as D-h proportional to alpha for alpha << 1 before dropping off as alpha(-1) for alpha > 1. Moreover, we show that the underlying spin dynamics at infinite temperature behaves qualitatively the same, albeit with important quantitative differences. We substantiate these findings by showing that the dynamics features self-similar scaling behavior, which strongly deviates from the Gaussian behavior of regular diffusion, especially for weak spin exchange. Finally, we show that the diffusion coefficient D-h follows an Arrhenius relation at high temperatures, whereby it is exponentially suppressed upon cooling.

10.1103/clhr-4h26

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