Interband Scattering and the “Metallic Phase” of Two-Dimensional Holes in GaAs<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>/</mml:mi></mml:math>AlGaAs

Yaish, Yuval; Prus, O.; Buchstab, E. I.; Shapira, Shachar; Yoseph, G. Ben; Sivan, Uri; Stern, Ady

doi:10.1103/physrevlett.84.4954

Cited by 47 publications

(57 citation statements)

References 25 publications

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“…ÿelds [145], inter-valley scattering [292], etc.-from the singular e ects due to impurities and interactions. The separation is at present a matter of some debate.…”

Section: Discussion Of the Experiments In Light Of The Theory Of Intementioning

confidence: 99%

Singular or non-Fermi liquids

2002

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“…ÿelds [145], inter-valley scattering [292], etc.-from the singular e ects due to impurities and interactions. The separation is at present a matter of some debate.…”

Section: Discussion Of the Experiments In Light Of The Theory Of Intementioning

confidence: 99%

Singular or non-Fermi liquids

2002

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“…The associated metal-toinsulator transition (MIT) has subsequently become the subject of intense interest and controversy [3]. While behavior similar to that of Ref.[2] has now been reported for a wide variety of 2D carrier systems such as n-AlAs, 10], and p-Si/SiGe [11,12], the origin of the metallic state and its transition into the insulating phase remain major puzzles in solid state physics.Several experiments have demonstrated the important role of the spin degree of freedom in the MIT problem, either in systems with a strong spin-orbit interaction [10,13,14], or via the application of an external magnetic field to spin polarize the carriers [15,16,17,18,19]. The latter experiments have shown that a magnetic field applied parallel to the 2DES plane suppresses the metallic temperature dependence, ultimately driving the 2DES into the insulating regime as the 2DES is spin polarized.…”

mentioning

confidence: 99%

“…Several experiments have demonstrated the important role of the spin degree of freedom in the MIT problem, either in systems with a strong spin-orbit interaction [10,13,14], or via the application of an external magnetic field to spin polarize the carriers [15,16,17,18,19]. The latter experiments have shown that a magnetic field applied parallel to the 2DES plane suppresses the metallic temperature dependence, ultimately driving the 2DES into the insulating regime as the 2DES is spin polarized.…”

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confidence: 99%

Spin–valley phase diagram of the two-dimensional metal–insulator transition

et al. 2007

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Using symmetry breaking strain to tune the valley occupation of a two-dimensional (2D) electron system in an AlAs quantum well, together with an applied in-plane magnetic field to tune the spin polarization, we independently control the system's valley and spin degrees of freedom and map out a spin-valley phase diagram for the 2D metal-insulator transition. The insulating phase occurs in the quadrant where the system is both spin-and valley-polarized. This observation establishes the equivalent roles of spin and valley degrees of freedom in the 2D metal-insulator transition.PACS numbers: 71.30.+h, 73.43.Qt, 73.50.Dn, The scaling theory of localization in two dimensions [1], which predicts an insulating phase for two-dimensional electron systems (2DESs) with arbitrarily weak disorder, was challenged by the observation of a metallic temperature dependence (dρ/dT > 0) of the resistivity, ρ, in low-disorder Si metal-oxide-semiconductor field-effect transistors (Si-MOSFETs) [2]. The associated metal-toinsulator transition (MIT) has subsequently become the subject of intense interest and controversy [3]. While behavior similar to that of Ref.[2] has now been reported for a wide variety of 2D carrier systems such as n-AlAs, 10], and p-Si/SiGe [11,12], the origin of the metallic state and its transition into the insulating phase remain major puzzles in solid state physics.Several experiments have demonstrated the important role of the spin degree of freedom in the MIT problem, either in systems with a strong spin-orbit interaction [10,13,14], or via the application of an external magnetic field to spin polarize the carriers [15,16,17,18,19]. The latter experiments have shown that a magnetic field applied parallel to the 2DES plane suppresses the metallic temperature dependence, ultimately driving the 2DES into the insulating regime as the 2DES is spin polarized. The relevance of multiple conduction-band valleys, on the other hand, is less known. Although it has been discussed theoretically that the occupation of multiple valleys may also be important [20,21], there has been no direct experimental demonstration. Here we show that the electrons' valley degree of freedom indeed plays a crucial role, analogous to that of spin. We study a 2DES, confined to an AlAs quantum well, in which we can independently tune both the spin and valley degrees of freedom. By studying the temperature dependence of ρ at various degrees of spin and valley polarization, we map out the metal-insulator phase diagram in this system at a constant density. The 2DES exhibits a metallic behavior when either the valley or spin are left fully unpolarized, and a minimum amount of both spin and valley polarization is required to enter the insulating phase.We performed experiments on 2DESs confined to modulation-doped, AlAs quantum wells of width 11 nm and 15 nm [22]. In these systems, the electrons occupy two conduction-band valleys of AlAs centered at the edges of the Brillouin zone along the [100] and [010] directions. We denote these valleys as X and Y...

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“…The hole density p in the 'metallic' region is varied by the gate voltage in the range (2.09 − 9.4) × 10 10 cm −2 , corresponding to the interaction parameter r s = 10 − 17 (with the effective mass m * taken as 0.38m e [9]). In [10,11] the 'metallic' character of a higher density 2DHG in GaAs was explained in terms of inelastic scattering between two hole subbands, split due to spin-orbit interaction. In our low-density structures the effect of the band splitting is negligible.…”

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Hole-Hole Interaction Effect in the Conductance of the Two-Dimensional Hole Gas in the Ballistic Regime

et al. 2002

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On a high mobility two-dimensional hole gas (2DHG) in a GaAs/GaAlAs heterostructure we study the interaction correction to the Drude conductivity in the ballistic regime, kBT τ /h > 1. It is shown that the 'metallic' behaviour of the resistivity (dρ/dT > 0) of the low-density 2DHG is caused by hole-hole interaction effect in this regime. We find that the temperature dependence of the conductivity and the parallelfield magnetoresistance are in agreement with this description, and determine the Fermi-liquid interaction constant F σ 0 which controls the sign of dρ/dT .It is well known that electron-electron interaction gives rise to a quantum correction to the classical (Drude) conductivity caused by impurity scattering [1]. Its manifestation can be quite different in the two regimes which relate the quasi-particle interaction time,h/k B T , to momentum relaxation time, τ : diffusive (k B T τ /h < 1), and ballistic (k B T τ /h > 1). So far the interaction correction to the conductivity of two-dimensional (2D) systems has been studied, both theoretically and experimentally, only in the diffusive regime, which is applicable to lowmobility (small τ ) systems [1]. Experimentally, the interaction correction was seen to be negative and produce a logarithmic decrease of the resistivity with increasing temperature, similar to the interference correction due to weak localisation (WL). Theory, however, suggests that the sign of the interaction effect in the diffusive regime can be different, dependent on the value of the interaction constant F σ 0 . Thus the correction can become positive and give rise to a 'metallic' temperature dependenceThe role of interactions in the conductance of 2D systems has now been intensely discussed, after the observation of the'metallic' behaviour in some low-density, highmobility 2D systems [3]. If one attempts to apply the conventional interaction theory, it can be seen that in high mobility structures the diffusion approximation becomes invalid even at low T . Recently, a theory of the interaction correction in the ballistic and intermediate regimes has been developed [4]. Stimulated by this theory, in this work we examine the role of the hole-hole interaction effects in a 2D hole gas (2DHG) which shows a 'metallic' ρ(T ). We analyse the temperature dependence of the conductivity and positive magnetoresistance in parallel field, and show that these two main features of the 'metallic' state can be explained by the interaction effect. It has the same origin as the logarithmic correction studied earlier [1], but now manifests itself in the ballistic regime.The interaction theory [4] considers elastic (coherent) electron scattering on the modulated density of other electrons (Friedel oscillation) caused by an impurity with a short-range potential. The phase of the Friedel oscillation, ∆p ∝ exp(i2k F r), is such that the wave scattered from the impurity interferes constructively with the wave scattered from the oscillation, Fig. 1 (a), leading to the quantum correction to the Drude conductivity σ...

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Interband Scattering and the “Metallic Phase” of Two-Dimensional Holes in GaAs/AlGaAs

Cited by 47 publications

References 25 publications

Singular or non-Fermi liquids

Singular or non-Fermi liquids

Spin–valley phase diagram of the two-dimensional metal–insulator transition

Hole-Hole Interaction Effect in the Conductance of the Two-Dimensional Hole Gas in the Ballistic Regime

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