z=2 Quantum Critical Dynamics in a Spin Ladder

Abstract

By means of inelastic neutron scattering we investigate finite temperature dynamics in the quantum spin ladder compound (C5H12N)2CuBr4 (BPCB) near the magnetic field induced quantum critical point with dynamical exponent z = 2. We observe universal finite-temperature scaling of the transverse local dynamic structure factor in spectacular quantitative agreement with longstanding theoretical predictions. At the same time, already at rather low temperatures, we observe strong non-universal longitudinal fluctuations. To separate the two, we make use of an intrinsic legexchange symmetry of the spin ladder. Complementary measurements of specific heat also reveal striking scaling behavior near the quantum critical point.

Spectral Function of a Boson Ladder in an Artificial Gauge Field

“…Exactly at the commensurate-incommensurate transition, the antisymmetric excitations are described by a gapless theory [48] with dynamical exponent z = 2. The finite temperature correlation function has a known scaling form [49,50], and the spectral function at the commensurate-incommensurate transition can be obtained by convolution of that correlation function with the one of the charge modes. Such calculation is left for future work.…”

Spectral Function of a Boson Ladder in an Artificial Gauge Field

“…Exactly at the commensurate-incommensurate transition, the antisymmetric excitations are described by a gapless theory [50] with dynamical exponent z = 2. The finite temperature correlation function has a known scaling form [51,52], and the spectral function at the commensurate-incommensurate transition can be obtained by convolution of that correlation function with the one of the charge modes. Such calculation is left for future work.…”

Finite-temperature dynamics and the role of disorder in nearly critical Ni(Cl1−xBrx)2·4SCFacheris1, Blosser2, Povarov3 et al. 2020Phys. Rev. BSelf Cite0000View full textAdd to dashboardCite

“…There, one has to look for the energy range where the dispersion is well approximated as parabolic. In most cases this constitutes a smaller fraction of the magnon bandwidth [34,35]. In particular, for the field-induced z = 2 transition in DTN, where the magnon bandwidth along the M-O line is under 0.2 meV ∼2 K [14], numerical studies show that scaling can only be expected to work for T 0.5 K [36].…”