Quantum spin liquids (QSLs) as novel phases of matter with long-range entanglement and deconfined quantum critical points (DQCPs) as descriptions for unconventional phase transitions between two ordered states beyond the standard paradigm, such as the transition between antiferromagnetic (AFM) and valence-bond solid (VBS) phases, are two representative emerging phenomena. These implications for understanding correlated materials and developing theoretical frameworks for many-body physics are of crucial importance. Here, we show that a gapless QSL can naturally emerge from a DQCP. Via large-scale tensor network simulations of a square-lattice spin-$1/2$ frustrated Heisenberg model, both QSL-state and DQCP-type AFM-VBS transitions are observed. By tuning the coupling constants, the AFM-VBS transition vanishes, and instead, a gapless QSL phase gradually develops in between. Remarkably, along the phase boundaries of AFM-QSL and QSL-VBS transitions, we always observe the same correlation-length exponents, $\nu \approx 1.0$, which is intrinsically different from the one of the DQCP-type transition, indicating new types of universality classes. Our results explicitly demonstrate a new scenario for understanding the emergence of gapless QSL from an underlying DQCP. The discovered QSL phase survives in a large region of tuning parameters, and we expect its experimental realization in solid-state materials or quantum simulators.

中文翻译：

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解限量子临界点无间隙量子自旋液体的出现

量子自旋液体 (QSL) 作为具有长程纠缠和解限量子临界点 (DQCP) 的新物质相，描述了超出标准范式的两个有序状态之间的非常规相变，例如反铁磁 (AFM) 和价态之间的转变-键固（VBS）相是两种具有代表性的新兴现象。这些对于理解相关材料和开发多体物理理论框架的意义至关重要。在这里，我们展示了无间隙 QSL 可以自然地从 DQCP 中出现。通过方格自旋的大规模张量网络模拟$1/2$受挫的海森堡模型，观察到 QSL 状态和 DQCP 型 AFM-VBS 转换。通过调整耦合常数，AFM-VBS 跃迁消失，取而代之的是，无间隙 QSL 阶段逐渐在其间发展。值得注意的是，沿着 AFM-QSL 和 QSL-VBS 跃迁的相界，我们总是观察到相同的相关长度指数，$\nu \approx 1.0$, 这与 DQCP 类型的转换本质上不同, 表明新类型的普遍性类。我们的结果明确地展示了一种从底层 DQCP 中理解无间隙 QSL 出现的新场景。发现的 QSL 相在大范围的调谐参数中仍然存在，我们期待它在固态材料或量子模拟器中的实验实现。