Are the interaction effects responsible for the temperature and magnetic field dependent conductivity in Si‐MOSFETs?

Pudalov, V. M.; Gershenson, M. E.; Kojima, H.; Brunthaler, G.; Bauer, G.

doi:10.1002/pssb.200303634

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“…By contrast, for the low-mobility samples Si-40 and Si-46, ρ(T ) varies by ≈ 15% only and its variation occurs at much higher temperatures and densities [67]. These well known features have been explored and understood earlier [58,59,62,[66][67][68].…”

Section: High-and Low-mobility Samplesmentioning

confidence: 99%

Novel energy scale in the interacting two-dimensional electron system evidenced from transport and thermodynamic measurements

2016

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We study how the non-Fermi-liquid two-phase state reveals itself in transport properties of highmobility Si-MOSFETs. We have found features in zero-field transport, magnetotransport, and thermodynamic spin magnetization in a 2D correlated electron system that may be directly related with the two-phase state. The features manifest above a density dependent temperature T * that represents a novel high-energy scale, apart from the Fermi energy. More specifically, in magnetoconductivity, we found a sharp onset of the novel regime δσ(B, T ) ∝ (B/T ) 2 above a density-dependent temperature T kink (n), a high-energy behavior that "mimics" the low-temperature diffusive interaction regime. The zero-field resistivity temperature dependence exhibits an inflection point T infl (n). In thermodynamic magnetization, the weak-field spin susceptibility per electron, ∂χ/∂n changes sign at T dM/dn (n). All three notable temperatures, T kink , T infl , and T dM/dn , behave critically ∝ (n − nc), are close to each other, and are intrinsic to high-mobility samples solely; we therefore associate them with an energy scale T * caused by interactions in the 2DE system. [5][6][7], metal-insulator transition (MIT) [1,5,[8][9][10], strong positive magnetoresistance (MR) in parallel field [11][12][13][14][15][16][17][18], strong renormalization of the effective mass and spin susceptibility [2,[19][20][21][22][23][24], etc.Far away from the critical MIT density n c , in the well "metallic regime," these effects are explained within the framework of the Fermi liquid theory -either in terms of interaction quantum corrections (IC) [25,26], or temperaturedependent screening of the disorder potential [27][28][29][30][31]. Both theoretical approaches so far are used to treat the experimental data on transport, and the former one -also to determine the Fermi liquid coupling constants from fitting the transport and magnetotransport data to the IC theory. In the close vicinity of the critical region, conduction is treated within the renormalization group [32][33][34][35][36], or the Wigner-Mott approach [37,38].On the other side, a number of theories predicts breakdown of the uniform paramagnetic 2D Fermi liquid state due to instability in the spin or charge channel, developing as interaction strength increases [39][40][41][42][43]. However, how the potential instabilities reveal themselves in charge transport remains an almost unexplored question.On the spin polarization of the 2D electron system Spin fluctuations are believed to play an important role in the 2DE system, especially near the apparent metalinsulator transition. Ferromagnetic instabilities result from the interplay of the electronic interactions and the Pauli principle. The interaction energy can be minimized when the fermion antisymmetry requirement is satisfied by the spatial wave function resulting in the alignment of spins and a large ground-state spin magnetization. In clean metals, the long-range part of the Coulomb interaction is screened, whereas its short-range part leads to s...

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