We consider gapped ${\mathbb{Z}}_{2}$ spin liquids, where spinon quasiparticles may carry fractional quantum numbers of space-group symmetry. In particular, spinons can carry fractional crystal momentum. We show that such quantum number fractionalization has dramatic, spectroscopically accessible consequences, namely, enhanced periodicity of the two-spinon density of states in the Brillouin zone, which can be detected via inelastic neutron scattering. This effect is a sharp signature of certain topologically ordered spin liquids and other symmetry-enriched topological phases. Considering square lattice space-group and time-reversal symmetry, we show that exactly four distinct types of spectral periodicity are possible.We consider gapped ${\mathbb{Z}}_{2}$ spin liquids, where spinon quasiparticles may carry fractional quantum numbers of space-group symmetry. In particular, spinons can carry fractional crystal momentum. We show that such quantum number fractionalization has dramatic, spectroscopically accessible consequences, namely, enhanced periodicity of the two-spinon density of states in the Brillouin zone, which can be detected via inelastic neutron scattering. This effect is a sharp signature of certain topologically ordered spin liquids and other symmetry-enriched topological phases. Considering square lattice space-group and time-reversal symmetry, we show that exactly four distinct types of spectral periodicity are possible.

arXiv:1401.1846Physical Review BSep 5, 201448 citations

Observation of Complex Bound States in the Spin- 1/2 Heisenberg XXZ Chain Using Local Quantum Quenches

Martin Ganahl, Elias Rabel, Fabian H. L. Eßler +1 more

We consider the nonequilibrium evolution in the spin-1/2 XXZ Heisenberg chain for fixed magnetization after a local quantum quench. This model is equivalent to interacting spinless fermions. Initially an infinite magnetic field is applied to n consecutive sites and the ground state is calculated. At time t=0 the field is switched off and the time evolution of observables such as the z component of spin is computed using the time evolving block decimation algorithm. We find that the observables exhibit strong signatures of linearly propagating spinon and bound state excitations. These persist even when integrability-breaking perturbations are included. Since bound states ("strings") are notoriously difficult to observe using conventional probes such as inelastic neutron scattering, we conclude that local quantum quenches are an ideal setting for studying their properties. We comment on implications of our results for cold atom experiments.We consider the nonequilibrium evolution in the spin-1/2 XXZ Heisenberg chain for fixed magnetization after a local quantum quench. This model is equivalent to interacting spinless fermions. Initially an infinite magnetic field is applied to n consecutive sites and the ground state is calculated. At time t=0 the field is switched off and the time evolution of observables such as the z component of spin is computed using the time evolving block decimation algorithm. We find that the observables exhibit strong signatures of linearly propagating spinon and bound state excitations. These persist even when integrability-breaking perturbations are included. Since bound states ("strings") are notoriously difficult to observe using conventional probes such as inelastic neutron scattering, we conclude that local quantum quenches are an ideal setting for studying their properties. We comment on implications of our results for cold atom experiments.

arXiv:1112.3355Physical Review LettersFeb 17, 2012117 citations

Spinon shift current in a noncentrosymmetric quantum spin chain

Anonymous, Shintaro Takayoshi, Takahiro Morimoto

We theoretically study direct current generation in a quantum spin chain induced by spinon excitations by light irradiation. We consider a $S=1/2$ one-dimensional (1D) antiferromagnetic XXZ model with magnetoelectric coupling that describes multiferroics with broken inversion symmetry. We perform the real-time simulation using infinite time-evolving block decimation, and demonstrate the direct current generation under light irradiation. By comparing the second order nonlinear conductivity and the two-spinon excitation spectra of a 1D XXZ model, we confirm that the spinon excitations are the origin for the direct current generation in the quantum spin chain. We find that the bulk photovoltaic effect is driven by electric polarization carried by the spinons through the shift current mechanism, and thus is regarded as ``the spinon shift current.''We theoretically study direct current generation in a quantum spin chain induced by spinon excitations by light irradiation. We consider a $S=1/2$ one-dimensional (1D) antiferromagnetic XXZ model with magnetoelectric coupling that describes multiferroics with broken inversion symmetry. We perform the real-time simulation using infinite time-evolving block decimation, and demonstrate the direct current generation under light irradiation. By comparing the second order nonlinear conductivity and the two-spinon excitation spectra of a 1D XXZ model, we confirm that the spinon excitations are the origin for the direct current generation in the quantum spin chain. We find that the bulk photovoltaic effect is driven by electric polarization carried by the spinons through the shift current mechanism, and thus is regarded as ``the spinon shift current.''

arXiv:2604.16063Physical review. B./Physical review. BAug 11, 20260 citations

We consider gapped

{\mathbb{Z}}_{2}

spin liquids, where spinon quasiparticles may carry fractional quantum numbers of space-group symmetry. In particular, spinons can carry fractional crystal momentum. We show that such quantum number fractionalization has dramatic, spectroscopically accessible consequences, namely, enhanced periodicity of the two-spinon density of states in the Brillouin zone, which can be detected via inelastic neutron scattering. This effect is a sharp signature of certain topologically ordered spin liquids and other symmetry-enriched topological phases. Considering square lattice space-group and time-reversal symmetry, we show that exactly four distinct types of spectral periodicity are possible.

We theoretically study direct current generation in a quantum spin chain induced by spinon excitations by light irradiation. We consider a

S=1/2

one-dimensional (1D) antiferromagnetic XXZ model with magnetoelectric coupling that describes multiferroics with broken inversion symmetry. We perform the real-time simulation using infinite time-evolving block decimation, and demonstrate the direct current generation under light irradiation. By comparing the second order nonlinear conductivity and the two-spinon excitation spectra of a 1D XXZ model, we confirm that the spinon excitations are the origin for the direct current generation in the quantum spin chain. We find that the bulk photovoltaic effect is driven by electric polarization carried by the spinons through the shift current mechanism, and thus is regarded as ``the spinon shift current.''