Spin effect on the low-temperature resistivity maximum in a strongly interacting 2D electron system

Abstract

The increase in the resistivity with decreasing temperature followed by a drop by more than one order of magnitude is observed on the metallic side near the zero-magnetic-field metal-insulator transition in a strongly interacting two-dimensional electron system in ultra-clean SiGe/Si/SiGe quantum wells. We find that the temperature $$T_{\text {max}}$$ T max , at which the resistivity exhibits a maximum, is close to the renormalized Fermi temperature. However, rather than increasing along with the Fermi temperature, the value $$T_{\text {max}}$$ T max decreases appreciably for spinless electrons in spin-polarizing (parallel) magnetic fields. The observed behaviour of $$T_{\text {max}}$$ T max cannot be described by existing theories. The results indicate the spin-related origin of the effect.

How to Recognize the Universal Aspects of Mott Criticality?

“…On the metallic side, a pronounced resistivity drop (often by a factor of 10 or more) is observed [24,30] below the temperature T max ∼ |n − n c | which decreases as the transition is approached. Characteristic scaling of the resistivity maxima has been reported in several systems [30][31][32], see Figure 3, which has been interpreted as evidence for strong correlation effects. However, the expected T 2 dependence of the resistivity has not been observed, despite the reported effective mass enhancement (m * ) −1 ∼ |n − n c | [36], characteristic of correlated Fermi liquids.…”

“…This idea suggests [27][28][29] that the melting of a Wigner solid by increasing density should be viewed as a Wigner-Mott transition, possibly bearing many similarities to Mott transitions in narrow-band crystalline solids such as Mott organics or transition-metal oxides. If this viewpoint is correct, then the resulting metal above the transition should display resemble other strongly correlated Fermi liquids, a notion that is starting to gain acceptance on the base of recent experiments [30][31][32].…”