Metallic Behavior of Cyclotron Relaxation Time in Two-Dimensional Systems

Abstract

Cyclotron resonance of two-dimensional electrons is studied at low temperatures down to 0.4 K for a high-mobility Si/SiGe quantum well which exhibits a metallic temperature dependence of dc resistivity ρ. The relaxation time τ(CR) shows a negative temperature dependence, which is similar to that of the transport scattering time τ(t) obtained from ρ. The ratio τ(CR)/τ(t) at 0.4 K increases as the electron density N(s) decreases, and exceeds unity when N(s) approaches the critical density for the metal-insulator transition.

In-plane magnetic field dependence of cyclotron relaxation time in a Si two-dimensional electron system

“…Recently, Masutomi et al have performed cyclotron resonance (CR) measurements on high-mobility Si 2D electron systems (2DESs). 18 The relaxation time τ CR , obtained from the linewidth, was found to be comparable to the transport scattering time τ t . It increases with decreasing temperature in a fashion similar to τ t .…”

“…The sample was fabricated from the same wafer as the one studied in Ref. 18. It is a Si/SiGe heterostructure with a 20-nm-thick strained Si QW sandwiched between relaxed Si 0.8 Ge 0.2 layers.…”

“…A two-axis vector magnet system was used to apply inde-pendently B and the perpendicular magnetic field B ⊥ for CR measurements. Instead of using a bolometer, 18 we observe electron heating in the 2DES under excitation at 100 GHz. A Hall bar sample, whose channel width is 200 µm, was mounted inside an oversized waveguide with an 8-mm bore inserted into a liquid-helium cryostat.…”