Measuring the Kondo Cloud by Current Cross Correlations in Helical Liquids

The Kondo cloud, represented by the correlations between the magnetic moment and the spin density in the leads of a Kondo setup, is until now eluding its observation. We exploit the unique coupling of spin and direction of motion of the recently discovered helical liquids in a setup with two leads to establish a proportionality between the Kondo cloud and the time resolved current cross correlations. This relation holds around a specific choice of model parameters. Thereby, we provide a new and direct way to detect the Kondo cloud.