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Condensed Matter > Strongly Correlated Electrons
Title: Gapless to gapless phase transitions by mode fractionalization in quantum spin chains
(Submitted on 1 Dec 2020 (this version), latest version 20 Jan 2022 (v3))
Abstract: We investigate spin chains with bilinear-biquadratic spin interactions as a function of an applied magnetic field $h$. At the Uimin-Lai-Sutherland (ULS) critical point we find a remarkable hierarchy of fractionalized excitations revealed by the dynamical structure factor $S(q,\omega)$ as a function of magnetic field yielding a transition from a gapless phase to another gapless phase before reaching the fully polarized state. At $h=0$, the envelope of the lowest energy excitations goes soft at two points $q_1=2\pi/3$ and $q_2=4\pi/3$, dubbed the A-phase. With increasing field, the spectral peaks at each of the gapless points bifurcate and combine to form a new set of fractionalized excitations that soften at a single point $q=\pi$ at $h_{c1}\approx 0.94$. Beyond $h_{c1}$ the system remains in this phase dubbed the B-phase until the transition at $h_{c2}=4$ to the fully polarized phase. We discuss the central charge of these two gapless phases and contrast the behavior with that of the gapped Haldane phase in a field.
Submission history
From: Shi Feng [view email][v1] Tue, 1 Dec 2020 18:03:22 GMT (2669kb,D)
[v2] Thu, 3 Dec 2020 03:40:24 GMT (2685kb,D)
[v3] Thu, 20 Jan 2022 06:39:19 GMT (7195kb,D)
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