Non-local and non-linear transport in SnTe multi-terminal topological microstructures

Abstract We fabricated six- and eight-terminal planar structures comprising sub-micron etched cross-junctions aligned along the [10], [01] and [11] crystallographic directions in 20 nm CdTe/SnTe/CdTe [001] quantum wells. Low-temperature magnetotransport measurements were performed to quantify the influence of lateral confinement on topological carrier states. Numerical calculations demonstrate that narrow SnTe channels host nearly dispersionless subbands, with the [11]-oriented channels exhibiting states that are markedly localized at mesa boundaries. Experimentally, disorder was found to substantially constrict the current paths associated with trivial bulk states, thereby suppressing channel conductivity. The resulting high-resistance junctions provide a suitable platform for non-local transport measurements, which indicate that electrical conduction is predominantly confined to the device edges. Furthermore, the differential resistance <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>R</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">d</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mi>I</mml:mi> <mml:mrow> <mml:mi>DC</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> </mml:math> , where <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>I</mml:mi> <mml:mrow> <mml:mi>DC</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> is the direct current flowing through a selected pair of contacts, exhibits a non-monotonic dependence below 1 K, characterized by an initial rise followed by a minimum, consistent with hydrodynamic electron flow in narrow quantum channels. In SnTe, such channels are plausibly formed by edge-localized topological states, in agreement with carrier parameters obtained from mobility spectrum analysis of macroscopic CdTe/SnTe/CdTe heterostructures.