scholarly journals Is there a Metallic State in Two Dimensions?

2000 ◽  
Vol 53 (4) ◽  
pp. 513
Author(s):  
A. R. Hamilton ◽  
M. Y. Simmons ◽  
M. Pepper ◽  
E. H. Linfield ◽  
P. D. Rose ◽  
...  
Keyword(s):  
Metallic Phase ◽  
Two Dimensions ◽  
Quantum Corrections ◽  
Metallic State ◽  
Hall Constant ◽  
Metal Insulator Transition ◽  
Parallel Magnetic Field ◽  
Metal Insulator ◽  
The One ◽  
Weak Electron

This paper reviews a series of experimental results on the metallic behaviour recently discovered in high quality, two-dimensional (2D) GaAs hole transistors. In particular, we address the question of what has happened to the two quantum corrections to the resistivity due to weak localisation and weak electron—electron interactions in the so-called metallic state. Detailed magnetoresistance data are presented just on the metallic side of the apparent metal—insulator transition, which show that both weak localisation (observed via negative magnetoresistance) and weak hole—hole interactions (giving a correction to the Hall constant) are present in the ‘metallic’ phase. The results suggest that as T→ 0 the resistivity will stop decreasing but turn up and tend towards infinity, in agreement with the early predictions of the one parameter scaling theory of localisation. The implication is that, even at high r s , there is no metallic phase at T = 0 in two dimensions. Other unexplained features of the anomalous ‘metallic’ state are also discussed, such as the destruction of metallic behaviour by a parallel magnetic field.

PERCOLATION APPROACH TO THE METAL–INSULATOR TRANSITION IN TWO DIMENSIONS

2001 ◽  
Vol 15 (19n20) ◽  
pp. 2641-2645
Author(s):  
YIGAL MEIR
Keyword(s):  
Magnetic Field ◽  
Critical Density ◽  
Metallic Phase ◽  
Two Dimensions ◽  
Insulator Transition ◽  
Exponential Dependence ◽  
Metal Insulator Transition ◽  
Electron Model ◽  
Metal Insulator ◽  
Model Combining

A simple non-interacting-electron model, combining local quantum tunneling via quantum point contacts and global classical percolation, is introduced in order to describe the observed "metal–insulator transition" in two dimensions.1 It is shown that many features of the experiments, such as the exponential dependence of the resistance on temperature on the metallic side, the linear dependence of the exponent on density, the e2/h scale of the critical resistance, the quenching of the metallic phase by a parallel magnetic field and the non-monotonic dependence of the critical density on a perpendicular magnetic field, can be naturally explained by the model.

scholarly journals A METAL–INSULATOR TRANSITION IN 2D: ESTABLISHED FACTS AND OPEN QUESTIONS

2010 ◽  
Vol 24 (12n13) ◽  
pp. 1640-1663 ◽  
Author(s):  
S. V. Kravchenko ◽  
M. P. Sarachik
Keyword(s):  
Two Dimensions ◽  
Insulator Transition ◽  
Metallic State ◽  
Electron Systems ◽  
Significant Progress ◽  
Metal Insulator Transition ◽  
Metallic Behavior ◽  
Metal Insulator ◽  
Open Questions ◽  
Experimental Findings

The discovery of a metallic state and a metal–insulator transition (MIT) in two-dimensional (2D) electron systems challenges one of the most influential paradigms of modern mesoscopic physics, namely, that "there is no true metallic behavior in two dimensions". However, this conclusion was drawn for systems of noninteracting or weakly interacting carriers, while in all 2D systems exhibiting the metal–insulator transition, the interaction energy greatly exceeds all other energy scales. We review the main experimental findings and show that, although significant progress has been achieved in our understanding of the MIT in 2D, many open questions remain.

Emergence of size induced metallic state in the ferromagnetic insulating Pr0.8Sr0.2MnO3 manganite: Breaking of surface polarons

2015 ◽  
Vol 8 (2) ◽  
pp. 2084-2093 ◽  
Author(s):  
PROLOY TARAN DAS ◽  
Arun Kumar Nigam ◽  
Tapan Kumar Nath
Keyword(s):  
Transport Properties ◽  
Metallic State ◽  
Temperature Dependent ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
System A ◽  
Surface Disorder ◽  
Bulk System ◽  
Magnetic Transport ◽  
Grain Surface

Nano-dimensional effects on electronic-, magneto-transport properties of granular ferromagnetic insulating (FMI) Pr0.8Sr0.2MnO3 (PSMO) manganite (down to 40 nm) have been investigated in details. From the electronic and magnetic transport properties, a metallic state has been observed in grain size modulation by suppressing the ferromagnetic insulating state of PSMO bulk system. A distinct metal-insulator transition (MIT) temperature around 150 K has been observed in all nanometric samples. The observed insulator to metallic transition with size reduction can be explained with surface polaron breaking model, originates due to enhanced grain surface disorder. This proposed phenomenological polaronic model plays a significant role to understand the polaronic destabilization process on the grain surface regime of these phase separated nano-mangnatie systems. Temperature dependent resistivity and magnetoresistance data in presence of external magnetic fields are investigated in details with various compatible models.

THE EFFECT OF HYDROSTATIC PRESSURE ON METAL–INSULATOR TRANSITION IN QUANTUM WELL SEMICONDUCTOR SYSTEMS II

2005 ◽  
Vol 04 (01) ◽  
pp. 45-53 ◽  
Author(s):  
A. JOHN PETER
Keyword(s):  
Hydrostatic Pressure ◽  
Quantum Well ◽  
Ionization Energy ◽  
Critical Concentration ◽  
Shallow Donor ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Mass Approximation ◽  
The One

Using a variational procedure within the effective mass approximation, the ionization energies of a shallow donor in a quantum well (QW) of GaAs/Ga 1-x Al x As superlattice system under the influence of pressure with the exact dielectric function are obtained. The vanishing of ionization energy initiating Mott transition is observed within the one-electron approximation. The effects of Anderson localization using a simple model, and exchange and correlation in the Hubbard model are included in this model. It is found that the ionization energy (i) increases when well width increases for a given pressure, (ii) decreases and reaches a bulk value for a larger well width, (iii) increases with increasing external hydrostatic pressure for a given QW thickness, and (iv) the critical concentration at which the metal–insulator transition (MIT) occurs is increased when pressure is applied. It also is demonstrated that MIT is not possible in a hydrostatic pressure in a quantum well supporting scaling theory of localization. All the calculations have been carried out with finite and infinite barriers and the results are compared with available data in the literature.

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