NMR evidence for a strong modulation of the Bose-Einstein Condensate in BaCuSi${}_2$O${}_6$

Abstract

We present a ${}^{63,65}$Cu and ${}^{29}$Si NMR study of the quasi-2D coupled spin 1/2 dimer compound BaCuSi${}_2$O${}_6$ in the magnetic field range 13-26 T and at temperatures as low as 50 mK. NMR data in the gapped phase reveal that below 90 K different intra-dimer exchange couplings and different gaps (${\Delta }_{\mathrm{B}}/{\Delta }_{\mathrm{A}}$ = 1.16) exist in every second plane along the c-axis, in addition to a planar incommensurate (IC) modulation. ${}^{29}$Si spectra in the field induced magnetic ordered phase reveal that close to the quantum critical point at $H_{c1}$ = 23.35 T the average boson density $\bar{n}$ of the Bose-Einstein condensate is strongly modulated along the c-axis with a density ratio for every second plane ${\bar{n}}_{\mathrm{A}}/{\bar{n}}_{\mathrm{B}}\simeq 5$. An IC modulation of the local density is also present in each plane. This adds new constraints for the understanding of the 2D value $\varphi$ = 1 of the critical exponent describing the phase boundary.

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Cited by in corpus (12)

• Bose-Einstein Condensation in Magnetic Insulators
• Theory of the field-induced BEC in the frustrated spin-1/2 dimer compound BaCuSi2O6
• Nuclear Magnetic Resonance in High Magnetic Field: Application to Condensed Matter Physics
• Phase separation versus supersolid behavior in frustrated antiferromagnets
• Reduced dimensionality in layered quantum dimer magnets: Frustration vs. inhomogeneous condensates
• Ab initio modeling of Bose-Einstein condensation in Pb2V3O9
• Revealing three-dimensional quantum criticality by Sr-substitution in Han Purple
• Two types of adjacent dimer layers in the low temperature phase of BaCuSi2O6
• Magnon Condensation in Dimerized Antiferromagnets with Spin-Orbit Coupling
• Crystal growth with oxygen partial pressure of the $BaCuS{i}_2{O}_6$ and $B{a}_{1-x}S{r}_{x}CuS{i}_2{O}_6$ spin dimer compounds
• Magnetic field-driven transition between valence bond solid and antiferromagnetic order in distorted triangular lattice
• Investigating field-induced magnetic order in Han Purple by neutron scattering up to 25.9 T