Localization of the Helical Edge States in the Absense of External Magnetic Field

Abstract

Theoretically, the helical edge states of two-dimensional topological insulators are protected from coherent backscattering due to nonmagnetic disorder provided electron interactions are not too strong. Experimentally, the edges typically do not demonstrate the systematic and robust quantization, at the same time little is known about the sub-Kelvin temperature behavior. Here, we report the surprising localization of the edge states in an 8 nm HgTe quantum well in zero magnetic field at millikelvin temperatures. Additionally, the magnetoresistance data at 0.5 K for the edges few micrometers long suggests the field-dependent localization length $l_B\propto B^{-\alpha }$, with $\alpha$ ranging approximately from $1.6$ to $2.8$ at fields $B\lesssim 0.1\text{T}$ and $\alpha \approx 1.1$ at higher fields up to $0.5\text{T}$. In the frame of disordered interacting edge, these values of $\alpha$ correspond to the Luttinger liquid parameters $K\approx 0.9-1.1$ and $K\approx 0.6$, respectively. We discuss possible scenarios which could result in the zero magnetic field localization.

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Cited by in corpus (3)

• Quantitative theory of backscattering in topological HgTe and (Hg,Mn)Te quantum wells: acceptor states, Kondo effect, precessional dephasing, and bound magnetic polaron
• Composite helical edges from Abelian fractional topological insulators
• Band manipulation and spin texture in interacting moiré helical edges