Quantum Hall effect and zero-resistance plateau in bulk HgTe

We investigate the quantum Hall effect (QHE) in a gated 1000-nm-thick HgTe film that nominally constitutes a three-dimensional system. Around the charge neutrality point (CNP), we observe a weak zero plateau in the Hall resistance, accompanied by a relatively small value of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:msub> <a:mi>R</a:mi> <a:mrow> <a:mi>x</a:mi> <a:mi>x</a:mi> </a:mrow> </a:msub> </a:math> on the order of <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mrow> <b:mi>h</b:mi> <b:mo>/</b:mo> <b:msup> <b:mi>e</b:mi> <b:mn>2</b:mn> </b:msup> </b:mrow> </b:math> . We demonstrate that the zero plateau arises from counterpropagating chiral electron-hole edge channels with suppressed interchannel scattering. This behavior resembles that of the quantum spin Hall effect; however, in our case, quasiballistic transport persists over macroscopic distances. We show that the QHE emerges within a two-dimensional (2D) accumulation layer near the gate, while the bulk of the film serves as an electron reservoir. Carrier exchange between the reservoir and the 2D layer gives rise to anomalous scaling of the QHE—not with respect to the CNP, but relative to the first electron plateau.