Nonperturbative Scaling Theory of Free Magnetic Moment Phases in Disordered Metals

Zhuravlev, A. K.; Zharekeshev, I. Kh.; Gorelov, Evgeny; Lichtenstein, A. I.; Mucciolo, Eduardo R.; Kettemann, Stefan

doi:10.1103/physrevlett.99.247202

Cited by 33 publications

(42 citation statements)

References 43 publications

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“…This is the subject of ongoing work and will be published elsewhere. 11 On the experimental side, the relevance of the distribution of the Kondo temperature to the low-temperature anomaly of the dephasing rate could be established by utilizing samples with lower diffusion constants, such as the lowmobility samples of AuPd, examined in Ref. 61 (see also Ref.…”

Section: Dephasing Due To Free Magnetic Moments In Disordered Mmentioning

confidence: 99%

“…The finite-size rescaling will be investigated in a future work using a more refined numerical technique. 11 It is important to remark that a finite-size scaling analysis was performed in Ref. 29 in the strong disorder limit only.…”

Section: B the Distribution Of Tkmentioning

confidence: 99%

“…In weakly disordered metals it is possible in principle to extract T K by fitting physical quantities such as the spin susceptibility and the electron dephasing rate versus temperature against the corresponding universal scaling function. While that scaling function may be modified itself by the disorder, 8,11 the Kondo screening is still governed by T K , and one may study its sample-to-sample fluctuations. Below, we show that these fluctuations may have a significant impact on the low-temperature properties of a metallic sample even in the thermodynamic, infinite volume limit.…”

Section: Introductionmentioning

confidence: 99%

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Disorder-quenched Kondo effect in mesoscopic electronic systems

Kettemann

Mucciolo

2007

Phys. Rev. B

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Nonmagnetic disorder is shown to quench the screening of magnetic moments in metals, the Kondo effect. The probability that a magnetic moment remains free down to zero temperature is found to increase with disorder strength. Experimental consequences for disordered metals are studied. In particular, it is shown that the presence of magnetic impurities with a small Kondo temperature enhances the electron's dephasing rate at low temperatures in comparison to the clean metal case. It is furthermore proven that the width of the distribution of Kondo temperatures remains finite in the thermodynamic (infinite volume) limit due to wave function correlations within an energy interval of order 1/τ , where τ is the elastic scattering time. When time-reversal symmetry is broken either by applying a magnetic field or by increasing the concentration of magnetic impurities, the distribution of Kondo temperatures becomes narrower.

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Section: Dephasing Due To Free Magnetic Moments In Disordered Mmentioning

confidence: 99%

Section: B the Distribution Of Tkmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Disorder-quenched Kondo effect in mesoscopic electronic systems

Kettemann

Mucciolo

2007

Phys. Rev. B

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“…Critical exchange coupling. -Recently, it was shown that the distribution of the exchange couplings J nn′ results in a wide bimodal distribution of the Kondo temperature and free magnetic moments [9,19,20,21]. This was at first obtained by solving the 1-loop Nagaoka-Suhl equation (NSE) [22] of the Kondo model in the representation of the eigenstates of H 0 .…”

mentioning

confidence: 99%

“…where N I = D/∆ I is the number of localized states with a finite wave function amplitude at the magnetic impurity site [21].…”

mentioning

confidence: 99%

Critical Metal Phase at the Anderson Metal-Insulator Transition with Kondo Impurities

2009

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It is well-known that magnetic impurities can change the symmetry class of disordered metallic systems by breaking spin and time-reversal symmetry. At low temperature these symmetries can be restored by Kondo screening. It is also known that at the Anderson metal-insulator transition, wave functions develop multifractal fluctuations with power law correlations. Here, we consider the interplay of these two effects. We show that multifractal correlations open local pseudogaps at the Fermi energy at some random positions in space. When dilute magnetic impurities are at these locations, Kondo screening is strongly suppressed. We find that when the exchange coupling J is smaller than a certain value J * , the metal-insulator transition point extends to a critical region in the disorder strength parameter and to a band of critical states. The width of this critical region increases with a power of the concentration of magnetic impurities.Fifty years after its proposal, the Anderson metal-insulator transition (AMIT) of disordered noninteracting electrons [1] continues to be intensively studied [2,3,4,5]. The AMIT is a quantum phase transition of second order where the localization length diverges with a critical exponent ν. The critical state is multifractal and characterized by a wide distribution of wave function amplitudes with a log-normal shape [5]. One aspect which remains less understood is the interplay between the AMIT of conduction electrons and the dynamics of the spin of magnetic impurities. These can be induced by energy levels below the Fermi energy such as the d-levels of transition metal impurities [6] or by localized electronic states such as the dopant levels in semiconductors [7]. Magnetic moments can enhance the spin susceptibility and the specific heat as has been observed in Si:P close to the AMIT [8,9]. When local magnetic moments interact with the conduction electrons by an exchange interaction, they can break both spin degeneracy and time-reversal symmetry (TRS) of the conduction electrons. Therefore, they are expected to change the symmetry class of the electronic system from orthogonal to unitary [10], changing the critical exponent ν, the critical electron density n c , and the critical disorder strength W c at which the transition occurs [11,12]. At sufficiently low temperatures, an additional effect comes into play. The antiferromagnetic exchange interaction between spin-1/2 local moments and the conduction electrons in a metal leads to a correlated electron state where a Kondo singlet is formed, screening the local moments at temperatures below the Kondo temperature T K . In this limit, the magnetic susceptibility χ approaches a constant value, as indicated in the left inset of Fig. 1, and the magnetic moments cease to break the TRS of the conduction electrons. The situation is quite different in the insulating phase, where local spectral gaps ∆ I prevent the development of the Kondo screening whenever the exchange coupling J between local moments and conduction electrons is below a criti...

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The quantum Hall effect in narrow quantum wires

Struck

Kawarabayashi

Zhuravlev

et al. 2008

Physica Status Solidi (b)

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The quantum phase diagram of disordered quantum wires in a strong magnetic field is reviewed. For uncorrelated disorder potential the 2‐terminal conductance, as calculated with the numerical transfer matrix method, shows zero temperature discontinuous transitions between exactly integer plateau values and zero. This is explained by the dimensional crossover of the bulk localisation length, which drives a transition from delocalised to localised edge states. In the thermodynamic limit, fixing the aspect ratio of the wire, there is a transition from the one dimensional chiral metal of extended edge states to localisation along the wire. In the vicinity of this chiral metal insulator transition (CMIT), states are identified which are superpositions of edge states with opposite chirality. The bulk contribution of such states is found to decrease with increasing wire width. Based on exact diagonalisation results for the eigenstates and their participation ratios, we conclude that these states are characteristic for the CMIT, and have the appearance of nonchiral edges states. Thereby these states are distinguishable from other states in the quantum Hall wire, namely, extended edge states, two‐dimensionally (2D) localized, quasi‐1D localized, and 2D critical states. In the presence of spatially correlated random potential we find with the numerical transfermatrix method that the potential correlation results in a shift of quantized conductance plateaus in long wires proportional to the strength of the random potential. This shift is found to be insensitive to the strength of magnetic fields and the same for all plateaus. A semiclassical explanation of this effect is proposed. We conclude with an outlook on modfications of the quantum phase diagram due to the spin degree of freedom of the electrons and their interactions. We discuss the stability of the phase diagram at finite temperature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Nonperturbative Scaling Theory of Free Magnetic Moment Phases in Disordered Metals

Cited by 33 publications

References 43 publications

Disorder-quenched Kondo effect in mesoscopic electronic systems

Disorder-quenched Kondo effect in mesoscopic electronic systems

Critical Metal Phase at the Anderson Metal-Insulator Transition with Kondo Impurities

The quantum Hall effect in narrow quantum wires

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