Extraordinary boundary correlations at deconfined quantum critical points
- 1University of Minnesota
Abstract
Recent years have seen a growing appreciation for the effects of quantum critical fluctuations on gapless boundary degrees of freedom. Here we consider the boundary dynamics of the non-compact \mathbb{CP}^{N-1} ℂ ℙ N − 1 (NCCP ^{N-1} N − 1 ) model in two spatial dimensions, with N N complex boson species coupled to a fluctuating \mathrm{U}(1) U ( 1 ) gauge field. These models describe quantum phase transitions beyond the Landau paradigm, such as the deconfined quantum critical point between superconducting (SC) and quantum spin Hall (QSH) phases. We show that, in a large- N N limit and with the bulk tuned to criticality, boundaries of the NCCP ^{N-1} N − 1 model display logarithmically decaying, or “extraordinary-log”, correlations. In particular, when monopole operators exhibit quasi-long-ranged order at the boundary, we find that the extraordinary-log exponent of the NCCP ^{N-1} N − 1 model in the large- N N limit is q=N/4 q = N / 4 , signifying a new family of boundary universality classes parameterized by N N . In the context of the QSH – SC transition, the quantum critical point inherits helical edge modes from the QSH phase, and this extraordinary-log behavior manifests in their Cooper pair correlations.
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BibTeX
@article{cui2026extraordinary,
title = {{Extraordinary boundary correlations at deconfined quantum critical points}},
author = {Hao-Ran Cui and Hart Goldman},
journal = {SciPost Physics},
year = {2026},
month = oct,
doi = {10.21468/scipostphys.21.4.103},
url = {https://scipost.org/10.21468/SciPostPhys.21.4.103},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Extraordinary boundary correlations at deconfined quantum critical points
AU - Hao-Ran Cui
AU - Hart Goldman
PY - 2026
DA - 2026/10/22
JO - SciPost Physics
DO - 10.21468/scipostphys.21.4.103
UR - https://scipost.org/10.21468/SciPostPhys.21.4.103
AB - Recent years have seen a growing appreciation for the effects of quantum critical fluctuations on gapless boundary degrees of freedom. Here we consider the boundary dynamics of the non-compact \mathbb{CP}^{N-1} ℂ ℙ N − 1 (NCCP ^{N-1} N − 1 ) model in two spatial dimensions, with N N complex boson species coupled to a fluctuating \mathrm{U}(1) U ( 1 ) gauge field. These models describe quantum phase transitions beyond the Landau paradigm, such as the deconfined quantum critical point between superconducting (SC) and quantum spin Hall (QSH) phases. We show that, in a large- N N limit and with the bulk tuned to criticality, boundaries of the NCCP ^{N-1} N − 1 model display logarithmically decaying, or “extraordinary-log”, correlations. In particular, when monopole operators exhibit quasi-long-ranged order at the boundary, we find that the extraordinary-log exponent of the NCCP ^{N-1} N − 1 model in the large- N N limit is q=N/4 q = N / 4 , signifying a new family of boundary universality classes parameterized by N N . In the context of the QSH – SC transition, the quantum critical point inherits helical edge modes from the QSH phase, and this extraordinary-log behavior manifests in their Cooper pair correlations.
SN - 2542-4653
ER -