Signatures of dephasing by mirror-symmetry breaking in weak-antilocalization magnetoresistance across the topological transition in Pb1−xSnxSe

Abstract

Many conductors, including recently studied Dirac materials, show saturation of coherence length on decreasing temperature. This surprising phenomenon is assigned to external noise, residual magnetic impurities, or two-level systems specific to noncrystalline solids. Here, by considering the SnTe-class of compounds as an example, we show theoretically that breaking of mirror symmetry deteriorates Berry's phase quantization, leading to additional dephasing in weak-antilocalization magnetoresistance (WAL-MR). Our experimental studies of WAL-MR corroborate these theoretical expectations in (111) Pb 1−x Sn x Se thin film with Sn contents x corresponding to both topological crystalline insulator and topologically trivial phases. In particular, we find the shortening of the phase coherence length in samples with intentionally broken mirror symmetry. Our results indicate that the classification of quantum transport phenomena into universality classes should encompass, in addition to time-reversal and spin-rotation invariances, spatial symmetries in specific systems.

Weak antilocalization beyond the fully diffusive regime in Pb1−xSnxSe topological quantum wells

“…A dramatic improvement of the transport properties of TCI single QWs is thus achieved approaching what has been realized in multiquantum wells and bulk materials. 16,45 While elastic scattering is dramatically reduced compared to other works, the inelastic scattering length is comparable to what was recently measured by Kazakov et al 15 This corroborates the reasoning that phonons or morphological defects (domain boundaries, surface scattering…) play a role in limiting quantum coherence in Pb1-xSnxSe.…”

“…Their coexistence with the 𝑇 −1/2 exponent rule can yield an intermediate decay exponent. Decay exponents exceeding 𝑝 = 0.5 have been reported in previous measurements on Pb1-xSnxSe with lower mobility and high carrier density, 44,15 ruling out a mechanism that is highly density dependent and favoring electron-phonon scattering as a possible explanation. A saturation of 𝐿 𝑇ℎ is also observed at 2K, however, more measurements at low temperature are needed to further understand this mechanism.…”

“…7,8,9,10 Trivial PbSe, PbTe and the ternary non-trivial Pb1-xSnxSe and Pb1-xSnxTe have been synthesized with superior quality in the form of bulk epilayers and heterostructures. 11,12,13,14,15,16,17 However, there has not been any effort dedicated to the synthesis of high-quality single QWs of the nontrivial class of those materials. Thus, while WAL has been extensively studied in TIs and spin-orbit coupled systems, it remains underexplored in TCIs -especially in high mobility samples.…”

Corner states, hinge states, and Majorana modes in SnTe nanowires

“…The realization of a 2D topological crystalline insulator phase would be particularly interesting, because in these systems a tunable breaking of the mirror symmetries would open a path for new device functionalities [14]. Indeed, the recent experiments in thin films of SnTe materials indicate that the transport properties of these systems can be controlled by intentionally breaking the mirror symmetry [15]. Furthermore, SnTe materials are promising candidate systems for studying the higher order topology [16,17].…”

Observation of Coexisting Weak Localization and Superconducting Fluctuations in Strained Sn1–xInxTe Thin Films

“…This spin–orbit splitting could originate from several possible sources. In Pb 1– x Sn x Se quantum wells, its origin is attributed to surface inversion asymmetry that introduces a Rashba-like term in the Hamiltonian describing the system . Band bending introduced in a controlled way by growing quantum wells with asymmetric barriers can have a similar effect .…”