Evidence for a quantum phase transition in two dimensions

• Published in: Physica A 2001-12, Vol.302 (1), p.368-374
• Main Authors: Sarachik, M.P., Vitkalov, S.A.
• Format: Article
• Language: English
• Subjects: Dilute two-dimensional systems; Metal–insulator transitions; Quantum phase transitions; Silicon inversion layers
• ISSN: 0378-4371; 1873-2119
• DOI: 10.1016/S0378-4371(01)00455-1

For a broad range of electron densities n and temperatures T, data for the in-plane magnetoconductance of the two-dimensional system of electrons in silicon MOSFET's is shown to collapse onto a universal curve using a single parameter H σ ( n, T); the scaling parameter H σ obeys the empirical relation H σ = A( n)[ Δ( n) 2+ T 2] 1/2. The characteristic energy k B Δ associated with the magnetic field dependence of the conductivity decreases with decreasing density, and extrapolates to 0 at a critical density n 0, signaling the approach to a zero-temperature quantum phase transition. For densities near n 0 H σ = AT so that the magnetoconductance scales with H/ T. We suggest that this behavior is associated with a ferromagnetic instability.