Year: 2025
Type: article
Abstract: We present a detailed study of the finite-size one-dimensional quantum XY chain in a transverse field in the presence of boundary fields coupled with the order-parameter spin operator. We consider fields located at the chain boundaries that have the same strength and that are oppositely aligned. We derive exact expressions for the gap Δ as a function of the model parameters for large values of the chain length L. These results allow us to characterize the nature of the ordered phases of the model. We find a magnetic (M) phase ( Δ ∼ e − a L ), a magnetic-incommensurate (MI) phase ( Δ ∼ e − a L f MI ( L ) ), a kink (K) phase ( Δ ∼ L − 2 ) and a kink-incommensurate (KI) phase ( Δ ∼ L − 2 f KI ( L ) ); f MI ( L ) and f KI ( L ) are bounded oscillating functions of L. We also analyze the behavior along the phase boundaries. In particular, we characterize the universal crossover behavior across the K-KI phase boundary. On this boundary, the dynamic critical exponent is z = 4, i.e. Δ ∼ L − 4 for large values of L.
Authors: Aldo Coraggio, Andrea Pelissetto
Language: English
Topic: Quantum many-body systems
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,290
OpenAlex ID: W4407135302