Quantum Breakthrough: Ultracold Fermions Unveil Exotic Skin Effect in 2D

By Hong Kong University of Science and Technology January 14, 2025

Collected at: https://scitechdaily.com/quantum-breakthrough-ultracold-fermions-unveil-exotic-skin-effect-in-2d/

Researchers have successfully simulated the non-Hermitian skin effect in a two-dimensional quantum system, a first in the field.

This groundbreaking work, which uses ultracold fermions, reveals potential for a deeper understanding of quantum systems interacting with their environment, paving the way for future discoveries in quantum physics and information.

Groundbreaking Quantum Simulation Achievement

A team of scientists led by The Hong Kong University of Science and Technology (HKUST) has achieved a major breakthrough by simulating the non-Hermitian skin effect in two dimensions using ultracold fermions. This accomplishment represents a significant step forward in the field of quantum physics.

Quantum mechanics traditionally focuses on systems that are isolated from their environment. It explains a wide range of phenomena, from how electrons behave in solids to how information is processed in quantum devices. These systems are typically described using a Hermitian model (Hamiltonian), which ensures observable properties like energy have real values and remain conserved.

Understanding Non-Hermitian Dynamics

However, when a quantum system interacts with its surroundings—exchanging particles or energy—the Hermitian model breaks down. Instead, such open systems are better described by a non-Hermitian Hamiltonian. This approach has unlocked new insights into quantum information, curved space, unusual topological phases, and even the physics of black holes. Yet, many mysteries about non-Hermitian quantum behavior, particularly in higher dimensions, remain unresolved.

In collaboration with Peking University (PKU), physicists from the two universities have simulated one such intriguing phenomenon—the non-Hermitian skin effect (NHSE)—which involves the accumulation of eigenstates at the boundary of an open system. This successful demonstration marks a crucial advancement, as previous experimental realizations of the non-Hermitian skin effect were limited to lower dimensions or classical systems rather than quantum systems.

Innovative Two-Dimensional Model Demonstrated

This finding is published in Nature on January 8, 2025. The research created a two-dimensional non-Hermitian topological band for ultracold fermions in spin-orbit-coupled optical lattices with tunable dissipation, unveiling the non-Hermitian skin effect, says Prof. Gyu-Boong Jo, Professor of Physics at HKUST leading the study.

“Our work unveils an intriguing system that allows us to explore how non-Hermiticity plays with symmetry and topology,” said Prof. Jo. “Our experiment naturally sets a quantum many-body system instead of classical systems, opening up avenues to investigate non-Hermitian quantum dynamics using ultracold fermions with dissipation.”

Exploring High-Dimensional Non-Hermitian Phenomena

Prof. Xiong-jun Liu, Professor at PKU and the other leader of the team added, “The interplay of higher-dimensional non-Hermitian skin effect with fundamental Hermitian scenarios, such as curved spaces, black holes, quantum information, and higher-order topological phases, necessitates exploration in many-body systems beyond a one-dimensional system. The high degree of control in our system positions it as a versatile platform for exploring high-dimensional non-Hermitian phenomena, offering insights into exotic quantum physics beyond the realms of condensed matter and ultracold atoms.”

The team emphasized that a complete understanding of the NHSE remains elusive, with key questions still unanswered: “Is there a general topological explanation for NHSE?” and “How much does topology determine its presence or absence?” “This reported work sets the stage for exploring such questions,” Prof. Jo added.

Reference: “Two-dimensional non-Hermitian skin effect in an ultracold Fermi gas” by Entong Zhao, Zhiyuan Wang, Chengdong He, Ting Fung Jeffrey Poon, Ka Kwan Pak, Yu-Jun Liu, Peng Ren, Xiong-Jun Liu and Gyu-Boong Jo, 8 January 2025, Nature.
DOI: 10.1038/s41586-024-08347-3