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Description
Low-dimensional materials with strong magnetic interaction, such as antiferromagnetic kagome layered systems, embody the characteristics of the perfect candidate for the research of the long-dreamt QSL (quantum spin liquid). The strong magnetic frustration arising from interacting spins in a kagome system might be the key to this novel phase, where disorder prevails over any magnetic ordering and where fractional excitations and entanglement are predicted. In this scenario, the recent realization of the Y3Cu9(OH)19Cl8 anisotropic kagome lattice system caught the attention. The anisotropy leads to three different Cu-O-Cu super-exchange interactions between the non-equivalent copper atoms [1]. The discovery of this compound prompted a detailed theoretical study, which highlighted two long-range magnetic ordering phases with propagation vector Q = (1/3,1/3) and Q = (0,0) and a spin liquid phase [2]. Experimental work confirmed the coplanar antiferromagnetic ground state at a Neel temperature of 2.1 K by the use of multiple experimental techniques such as NMR, μSR, and INS. The latter also determined the magnetic exchange couplings, positioning the system close to the border of the spin liquid phase [3]. This work focuses on how to tune the three different magnetic couplings with state-of-the-art high-pressure and low temperature single crystal X-ray diffraction measurements at the ID27 beamline of ESRF and to show how the pressure-induced modifications in Cu-O-Cu angle can directly influence the magnitude of the magnetic exchange, driving the system toward the spin liquid state. Moreover, it addresses these changes from an ab-initio perspective, further corroborating the trend towards the spin liquid phase with increased hydrostatic pressure and proving how the magnetic couplings are sensitive to the Cu-O-Cu angle and hydrogen position. Complementary μSR data under pressure shows that the magnetic ground state is surprisingly sensitive to the applied pressure, and that under a moderate 2 GPa pressure, the frustration increase is sufficient to induce a fluctuating ground state [4]. This work also addresses initial INS measurement at the extreme condition of 100 mK and 1 GPa, showing the remarkable appearance of magnetic excitation, paving the way to find fingerprints of fractionalized excitations and entanglement at higher pressure. The suppression of long-range ordering with pressure tuning is a remarkable step towards the realization of a well-control spin liquid ground state.