Magnetic excitations and transport properties in frustrated ferromagnetic chain

フラストレート強磁性鎖の磁気励起と輸送特性

大西 弘明  

Onishi, Hiroaki

In a spin nematic state of a spin-1/2 frustrated ferromagnetic chain, low-energy excitations are governed by bound magnons, so that bound magnons carry spin current and thermal current. Regarding magnetic excitations, we find gapless longitudinal and gapped transverse spin excitation spectra, in accordance with quasi-long-range longitudinal and short-range transverse spin correlations, respectively, while we observe gapless quadrupole excitations, signaling quasi-long-range quadrupole correlations. In the present work, we investigate spin and thermal transport properties by exploiting numerical methods, such as exact diagonalization and density-matrix renormalization group. We will discuss the effects of bound magnon propagation in spin and thermal transport, based on detailed analyses of current-current correlation functions in the spin nematic ground state, and temperature and field dependencies of the spin Drude weight and the thermal Drude weight.