Self-organized magnon condensation in quasi-one-dimensional edge-shared cuprates

Magnon dynamics in quantum magnetism have long sparked interest in condensed matter physics. Since Bethe's prediction nearly a century ago, multimagnon bound states have presented significant potential for both fundamental insights and technological applications. Despite this, observing these bound states in natural materials has been challenging, partly due to the prevailing view that high magnetic fields are necessary for their stabilization. Here, we demonstrate that low-dimensional spin systems, specifically quasi-one-dimensional edge-shared cuprates, offer a promising landscape for realizing multimagnon bound states through a novel stabilization mechanism. This approach leverages small antiferromagnetic interchain couplings that act as effective internal magnetic fields, promoting collinear antiferromagnetic order and fostering self-organized magnon condensation at lower field strengths. By circumventing the need for high external fields, this mechanism provides a more experimentally accessible pathway, with implications for developing magnon-based quantum computing architectures, low-power spintronic devices, and high-speed magnonic circuits for efficient information processing. Our study presents a theoretical framework, supported by numerical simulations and experimental data from quasi-one-dimensional cuprates such as Li2CuO2, Ca2Y2Cu5O10, LiCuSbO4, and PbCuSO4(OH)2. Beyond practical applications, our findings reveal that small interchain couplings can induce previously unobserved magnetic phenomena, offering new insights into the nature of magnetic ordered states.