What causes the metallic resistance drop in dilute 2D electron systems? · revision history
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- Title
- What causes the metallic resistance drop in dilute 2D electron systems?
- Plain
- In clean silicon devices with few electrons, resistance falls by up to about ten times on cooling below a few kelvin, the opposite of what weak-disorder theory predicts. Which physical process causes this drop is disputed.
- Precise
- In Si-MOSFETs, Si/SiGe and p-GaAs two-dimensional systems at $r_s \sim 10-40$ ($r_s$ = mean interparticle spacing in units of the effective Bohr radius), $\rho(T)$ on the metallic side falls by up to an order of magnitude for $T$ below roughly $0.1-0.3\,E_F$, and an in-plane field that polarizes the spins suppresses the drop. Identify the mechanism among temperature-dependent screening of charged impurities, ballistic interaction corrections (Zala, Narozhny and Aleiner), the two-parameter renormalization group of the disordered Fermi liquid (Finkelstein; Punnoose and Finkelstein), and Pomeranchuk-type physics of a Wigner-crystal and liquid mixture (Spivak and Kivelson). An answer is one framework that fits $\rho(T,n,B_{\mathrm{parallel}})$ quantitatively across materials with independently measured parameters.
- Settled by
- A quantitative fit of rho(T, n, B_parallel) in several materials, with impurity density and Fermi-liquid parameters fixed by independent measurements, that excludes the competing mechanisms.
- Kind
- phenomenon
- Answer type
- mechanism
- References
- (empty)
- Literature status
- contested
- Status note
- Groups still disagree on whether screening theory accounts for the data; a 2021 review of ultra-clean Si systems argues for interaction-driven physics (arXiv 2102.00114).
- Posed since
- 1994