Phantom Bethe excitations and spin helix eigenstates in integrable periodic and open spin chains

Popkov, Vladislav (avtor), Zhang, Xin (avtor), Klümper, Andreas (avtor)

We demonstrate the existence of a special chiral “phantom” mode with some analogy to a Goldstone mode in the anisotropic quantum XXZ Heisenberg spin chain. The phantom excitations contribute zero energy to the eigenstate, but a finite fixed quantum of momentum $k_0$. The mode exists not due to symmetry principles, but results from nontrivial scattering properties of magnons with momentum $k_0$ given by the anisotropy via $\cos{k_0}=\Delta$. Different occupations of the phantom mode lead to energetical degeneracies between different magnetization sectors in the periodic case. This mode originates from special string-type solutions of the Bethe ansatz equations with unbounded rapidities, the phantom Bethe roots (PBRs). We derive criteria under which the spectrum contains eigenstates with PBRs, both in open and periodically closed integrable systems, for spin-1/2 and higher spins, and discuss the respective chiral eigenstates. The simplest of such eigenstates, the spin helix state, which is a periodically modulated state of chiral nature, is built up from the phantom excitations exclusively. Implications of our results for experiments are discussed.

• Jezik: Angleški jezik
• Ključne besede: quantum mechanics
• Tipologija: 1.01 - Izvirni znanstveni članek
• Organizacija: FMF - Fakulteta za matematiko in fiziko
• Status publikacije: Objavljeno
• Različica publikacije: Recenzirani rokopis
• Leto izida: 2021
• Št. strani: Str. L081410-1-L081410-6
• Številčenje: Vol. 104, iss. 8
• PID: 20.500.12556/RUL-134624
• UDK: 530.145
• ISSN pri članku: 2469-9950
• DOI: 10.1103/PhysRevB.104.L081410
• COBISS.SI-ID: 94433027
• Datum objave v RUL: 21.01.2022

Gradivo je del revije

• Naslov: Physical review
• Založnik: American Physical Society
• ISSN: 2469-9950
• COBISS.SI-ID: 2997348

Sekundarni jezik

• Jezik: Slovenski jezik
• Ključne besede: kvantna mehanika

Projekti

• Financer: EC - European Commission
• Program financ.: H2020
• Številka projekta: 694544
• Naslov: Open Many-body Non-Equilibrium Systems
• Akronim: OMNES