Hidden quantum spin gap state in the static stripe phase of La$_{2-x}$Sr$_{x}$CuO$_{4}$

TL;DR

This study reveals a hidden quantum spin gap in the static stripe phase of La_{2-x}Sr_xCuO_4, showing how spin excitations evolve with doping and indicating phase separation of magnetic states.

Contribution

It provides new insights into the spin excitation spectrum and phase separation in La_{2-x}Sr_xCuO_4 using neutron scattering, highlighting a quantum spin gap in the stripe phase.

Findings

Existence of a 4 meV spin gap in the static stripe phase.

Spectral weight shifts from quasi-elastic to gapped excitations with doping.

Evidence of phase separation of magnetic phases.

Abstract

Low energy spin excitations were investigated in the static stripe phase of La_{2-x}Sr_xCuO_4 using elastic and inelastic neutron scattering on single crystals. For x = 1/8 in which long-range static stripe order exists, an energy gap of E_g = 4 meV exists in the excitation spectrum in addition to strong quasi-elastic, incommensurate spin fluctuations associated with the static stripes. When x increases, the spectral weight of the spin fluctuations shifts from the quasi-elastic continuum to the excitation spectrum above E_g. The dynamic correlation length as a function of energy and the temperature evolution of the energy spectrum suggest a phase separation of two distinct magnetic phases in real space.