Enhancement of spin susceptibility of low-density two-dimensional electrons in a high quality Si/SiGe quantum well

We report magneto-transport measurement results of two-dimensional electrons in a high quality Si/SiGe quantum well under tilted magnetic fields. The electron peak mobility reaches 2 x 10$^{6}$ cm$^{2}$/Vs and the density is varied from 0.8 to 2.1 x 10$^{11}$ cm$^{-2}$. Under tilted magnetic fields, two Landau levels with opposite spins are brought into energetic coincidence. From the coincidence angles we determine the effective spin susceptibility g*m*. At n $=$2.1 x 10$^{11}$ cm$^{-2}$, g*m* $\sim$ 4 (in units of m$_{\mathrm{b}}$g$_{\mathrm{b}})$, consistent with previous work [Lai et al, PRL 96, 076805 (2006)]. Our results further show that the spin susceptibility is enhanced by 20{\%} at 0.8 x 10$^{11}$ cm$^{-2}$ from its high density value. Surprisingly, unlike previous results in modulation doped Si/SiGe quantum wells, a resistance peak is observed at nu$=$3 when Landau level coincidence occurs in our undoped Si/SiGe field-effect transistor sample. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.