RQC Seminar

116th RQC Seminar

• Speaker

  Dr. Nicolò D'Anna
  ( The University of California San Diego (UCSD), USA )

• Date

  16:00-17:00, May 21, 2024 (Tuesday)

• Venue

  Hybrid(ZOOM・ Wako Main Research 3F 345-347 Seminar Room/ 研究本館3階 セミナー室(345-347) C01）

• Title

  Evidences of a hidden inhomogeneous phase in the world's most common semiconductor: temperature and density dependence of electron-transport in group-V doped silicon

• Inquiries

  rqc_info[at]ml.riken.jp

Abstract
We report on magneto-transport evidence of an inhomogeneous phase in two-dimensional dopant layers in silicon, near the metal-to-insulator transition, associated with an anomalous Hall response and hysteresis. In this work we use gas-phase dosing of dopant precursor molecules on silicon to create arsenic and phosphorus δ-layers as thin as 0.4 nm and as dilute as 10^13 cm−2. We show that for such low dopant densities electron-electron interactions play an important role in the magneto- transport through the isotropic (in magnetic field) Zeeman effect, and we show how the Zeeman and conventional weak-localisation effects combine additively to yield the net magnetoconductivity. In addition, we show that when the δ-layers are cooled below ≈ 300 mK, they cross over to an inhomogeneous state where more conducting and more localised/insulating regions coexist. The associated random anisotropy of the sample is reflected in a significant increase of the transverse voltage Vxy response (even in magnetic field). Inelastic scattering of the diffusive electrons on the insulating inclusions acts as a temperature independent cut-off to the coherence length, and causes the conductivity to saturate at low temperatures. For dilute layers, the low temperature phase is marked by a hysteretic longitudinal and transverse magneto-conductance, an anomalous even Vxy effect, and anisotropic conduction.