Field-Induced Bose-Einstein Condensation of Triplons up to 8 K in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Sr</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi>Cr</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="bold">O</mml:mi><mml:mn>8</mml:mn></mml:msub></mml:math>

Single crystals of the spin dimer system ${\mathrm{Sr}}_{3}{\mathrm{Cr}}_{2}{\mathrm{O}}_{8}$ have been grown for the first time. Magnetization, heat capacity, and magnetocaloric effect data up to 65 T reveal magnetic order between applied fields of ${H}_{c1}\ensuremath{\sim}30.4\text{ }\text{ }\mathrm{T}$ and ${H}_{c2}\ensuremath{\sim}62\text{ }\text{ }\mathrm{T}$. This field-induced order persists up to ${T}_{c}^{\mathrm{max}}\ensuremath{\sim}8\text{ }\text{ }\mathrm{K}$ at $H\ensuremath{\sim}44\text{ }\text{ }\mathrm{T}$, the highest observed in any quantum magnet where ${H}_{c2}$ is experimentally accessible. We fit the temperature-field phase diagram boundary close to ${H}_{c1}$ using the expression ${T}_{c}=A(H\mathrm{\text{\ensuremath{-}}}{H}_{c1}{)}^{\ensuremath{\nu}}$. The exponent $\ensuremath{\nu}=0.65(2)$, obtained at temperatures much smaller than ${T}_{c}^{\mathrm{max}}$, is that of the 3D Bose-Einstein condensate (BEC) universality class. This finding strongly suggests that ${\mathrm{Sr}}_{3}{\mathrm{Cr}}_{2}{\mathrm{O}}_{8}$ is a new realization of a triplon BEC where the universal regimes corresponding to both ${H}_{c1}$ and ${H}_{c2}$ are accessible at $^{4}\mathrm{He}$ temperatures.

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