Disorder-induced Revival of the Bose-Einstein Condensation in Ni(Cl₁₋ₓBrₓ)₂-4SC(NH₂)₂ at High Magnetic Fields

الأصل · EN

Building on recent NMR experiments [Phys. Rev. Lett. 118, 067203], we theoretically investigate the high magnetic field regime of the disordered quasi-one-dimensional S=1 antiferromagnetic material Ni(Cl₁₋ₓBrₓ)₂-4SC(NH₂)₂. The interplay between disorder, chemically controlled by Br-doping, interactions, and the external magnetic field, leads to a very rich phase diagram. Beyond the well-known antiferromagnetically ordered regime, analog of a Bose condensate of magnons, which disappears when H≥ 12.3 T, we unveil a resurgence of phase coherence at higher field H 13.6 T, induced by the doping. Interchain couplings stabilize finite temperature long-range order whose extension in the field - temperature space is governed by the concentration of impurities x. Such a "mini-condensation" contrasts with previously reported Bose-glass physics in the same regime, and should be accessible to experiments.