Spin current pumping in helical Luttinger liquids
  We study the DC spin current induced into an unbiased quantum spin Hall system through a two-point contacts setup with time dependent electron tunneling amplitudes. By means of two external gates, it is possible to drive a current with spin-preserving and spin-flipping contributions showing peculiar oscillations as a function of pumping frequency, electron-electron interaction and temperature. From its interference patterns as a function of the Fabry-Perot and Aharonov-Bohm phases, it is possible to extract information about the helical nature of the edge states and the intensity of the electron-electron interaction. 
Dario Ferraro, Giacomo Dolcetto, Roberta Citro, Francesco Romeo, Maura   Sassetti
cond-mat.mes-hall