Quantum criticality in the coupled two-leg spin ladder Ba2CuTeO6

Abstract

We report on zero-field muon spin rotation, electron spin resonance and polarized Raman scattering measurements of the coupled quantum spin ladder Ba2CuTeO6. Zero-field muon spin rotation and electron spin resonance probes disclose a successive crossover from a paramagnetic through a spin-liquid-like into a magnetically ordered state with decreasing temperature. More significantly, the two-magnon Raman response obeys a T -linear scaling relation in its peak energy, linewidth and intensity. This critical scaling behavior presents an experimental signature of proximity to a quantum critical point from an ordered side in Ba2CuTeO6.

Site-Selective d10/d0 Substitution in an S = 1/2 Spin Ladder Ba2CuTe1–xWxO6 (0 ≤ x ≤ 0.3)

“…36 Ba2CuTeO6 is an excellent system to test this due to its hexagonal perovskite structure that results in a spin ladder magnetic geometry. [37][38][39][40] Within the spin ladder, Cu 2+ cations are linked via three key Cu-O-Te-O-Cu exchange interactions illustrated in Figure 1c. These are the intraladder Jleg and Jrung interactions via the corner-sharing Te(1)O6 units and the inter-ladder interaction via the face-sharing Te(2)O6 units within the Cu-Te(2)-Cu trimers.…”

“…37 However, the low dimensional magnetic behavior means the system does not present a classical AFM ordering cusp. Instead, magnetic order has been detected using muon and neutron techniques placing the magnetic transition at TN = 14 K. 38,40 The W 6+ doped samples are similar in that they all display the same broad Tmax feature, but the position of Tmax shifts to lower temperatures as x increases as shown in Table 2, suggesting weakening of the short-range ladder interactions. More dramatic differences are observed at low temperatures, where the upturn in the susceptibility data gradually becomes stronger with x and this 'Curie-tail' like feature is most pronounced in the x = 0.3 sample.…”

“…Ba2CuTeO6 is known to lie on the ordered side of the S = 1/2 spin ladder phase diagram, but is very close to the quantum critical point between the Néel ordered and spin-singlet states. 38,40,[62][63][64][65] The introduction of W 6+ d 0 to the B''(c) site could modify the ratio between the Jleg and…”

Spin dynamics of coupled spin ladders near quantum criticality in Ba2CuTeO6

“…It may be worthwhile for future research to examine in more detail the evolution of the spectral function within this elevated energy range as a function of the interladder coupling strength, connecting these single-ladder results to the strongly coupled case. The room-temperature crystal structure of Ba 2 CuTeO 6 is monoclinic (C2/m), and a weak structural distortion to a triclinic phase (P1) occurs at T S = 287 K. 21,22 We use throughout the higher symmetry monoclinic unit cell description, since the triclinic distortion is very small. The monoclinic lattice parameters are a = 10.2444(3)Å, b = 5.7315(2)Å, c = 10.1055(5)Å, and β = 108.019(3) • at T = 296 K. 21 Ignoring this small distortion, the transformation from the monoclinic lattice basis vectors (a, b, c) to the triclinic ones (a t , b t , c t ) is given by…”

“…Ba2CuTeO6 has been proposed to be located close to the quantum critical point, on the ordered side of the phase diagram. 21,22…”