signature=3722b368fe33fa0a6e1192bce52663d8,Signatures of fractionalization in the field orientation ...

摘要：

The main question we address is how to probe the fractionalized excitations of a quantum spin liquid, for example, in the Kitaev honeycomb model. We propose distinct signatures in the dynamical response of the spin-spin correlation function and its dependence on the magnitude and direction of a magnetic field in order to distinguish different phases. For antiferromagnetic (AF) Kitaev exchange couplings, the observed level crossing develops a gap as the field is rotated from the $[111]$ to the $[001]$ direction. Also, the large number of modes in the dynamical response are greatly reduced as the field is rotated toward $[001]$ resulting in a clearly discernible beating pattern in the time-dependent spin-spin correlation function, possibly observable in pump-probe experiments. We further observe a change in the nature of the lowest lying excitations from single spin-flips for fields along $[111]$, to double spin-flips for fields along $[001]$. Finally, via an analysis of the plaquette flux operator, we determine the field strength and orientation dependence of the non-Abelian Kitaev quantum spin-liquid phase, the enigmatic intermediate phase (for AF couplings only), and the partially polarized phase. Our results are obtained using exact diagonalization on finite clusters with periodic boundary conditions.

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