scholarly journals Many-body Spin Interactions in Semiconductor Quantum Wires

2000 ◽  
Vol 53 (4) ◽  
pp. 543 ◽  
Author(s):  
D. J. Reilly ◽  
L. N. Pfeiffer ◽  
G. R. Facer ◽  
K. W. West ◽  
A. S. Dzurak ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Applied Magnetic Field ◽  
Quantum Wires ◽  
Zero Magnetic Field ◽  
Point Contacts ◽  
Many Body ◽  
Temperature Dependent ◽  
Modulation Doping ◽  
Dominant Mechanism ◽  
Spin Interactions

Zero length quantum wires (or point contacts) exhibit unexplained conductance structure close to 0.7 � 2e 2 /h in the absence of an applied magnetic field. We have studied the density- and temperature-dependent conductance of ultra-low-disorder GaAs/AlGaAs quantum wires with nominal lengths l=0 and 2�m, fabricated from structures free of the disorder associated with modulation doping. In a direct comparision we observe structure near 0.7 � 2e 2 /h for l = 0, whereas thel = 2�m wires show structure evolving with increasing electron density to 0.5 � 2e 2 /h in zero magnetic field, the value expected for an ideal spin-split sub-band. Our results suggest the dominant mechanism through which electrons interact can be strongly affected by the length of the 1D region.

Point-contact spectroscopy probing the NbSe3 CDW gap in different crystallographic orientations

2002 ◽  
Vol 12 (9) ◽  
pp. 119-122
Author(s):  
A. A. Sinchenko ◽  
P. Monceau
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Applied Magnetic Field ◽  
Energy Gap ◽  
Point Contact ◽  
Point Contacts ◽  
Energy Gaps ◽  
Current Voltage ◽  
Current Voltage Characteristics ◽  
Crystallographic Orientations

We have measured the differential current-voltage characteristics of normal metal-NbSe3 direct point contacts (without insulating barrier) formed along different crystallographic orientations under applied magnetic field with different orientations. At low temperature two energy gaps, $\Delta_{p1}$ and $\Delta_{p2}$, corresponding to the high and the low-temperature CDW were observed simultaneously as a singulanty of the excess resistance which is attributed to an analog of Andreev reflection, in which the incident electron reflects on the Peierls energy gap barriers with its charge unchanged. An applied magnetic field up to 8.5 T does not lead to a change in the density of states and in the Peierls energy gaps, suggesting that the large magnetoresistance observed in NbSe3 might not result from the change in the CDW order parameter with magnetic field but rather from the increase of scattering of non-condensed to CDW carriers.

scholarly journals Nonsaturating large magnetoresistance in semimetals

2018 ◽  
Vol 115 (42) ◽  
pp. 10570-10575 ◽  
Author(s):  
Ian A. Leahy ◽  
Yu-Ping Lin ◽  
Peter E. Siegfried ◽  
Andrew C. Treglia ◽  
Justin C. W. Song ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Transport Properties ◽  
Applied Magnetic Field ◽  
Charge Compensation ◽  
Linear Dispersion ◽  
Dominant Mechanism ◽  
Temperature Dependences ◽  
Topological Semimetals ◽  
Different Origins

The rapidly expanding class of quantum materials known as topological semimetals (TSMs) displays unique transport properties, including a striking dependence of resistivity on applied magnetic field, that are of great interest for both scientific and technological reasons. So far, many possible sources of extraordinarily large nonsaturating magnetoresistance have been proposed. However, experimental signatures that can identify or discern the dominant mechanism and connect to available theories are scarce. Here we present the magnetic susceptibility (χ), the tangent of the Hall angle (tan⁡θH), along with magnetoresistance in four different nonmagnetic semimetals with high mobilities, NbP, TaP, NbSb2, and TaSb2, all of which exhibit nonsaturating large magnetoresistance (MR). We find that the distinctly different temperature dependences, χ(T), and the values of tan⁡θH in phosphides and antimonates serve as empirical criteria to sort the MR from different origins: NbP and TaP are uncompensated semimetals with linear dispersion, in which the nonsaturating magnetoresistance arises due to guiding center motion, while NbSb2 and TaSb2 are compensated semimetals, with a magnetoresistance emerging from nearly perfect charge compensation of two quadratic bands. Our results illustrate how a combination of magnetotransport and susceptibility measurements may be used to categorize the increasingly ubiquitous nonsaturating large magnetoresistance in TSMs.

EFFECT OF Ba SUBSTITUTION ON ELECTRICAL TRANSPORT AND MAGNETORESISTANCE OF La1.2Sr1.8Mn2O7

2009 ◽  
Vol 23 (03) ◽  
pp. 447-460 ◽  
Author(s):  
Y. S. REDDY ◽  
P. KISTAIAH ◽  
C. VISHNUVARDHAN REDDY
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Applied Magnetic Field ◽  
Electrical Transport ◽  
Sol Gel ◽  
Parent Compound ◽  
Temperature Dependent ◽  
Temperature Range ◽  
Anisotropic Lattice ◽  
Ba Substitution

Polycrystalline samples of double layered (DL) manganite system La 1.2( Sr 1-x Ba x)1.8 Mn 2 O 7(0.0≤×≤0.4) were prepared by the sol-gel method. The anisotropic lattice expansion is observed with the substitution of Ba 2+ into Sr 2+ sites. The electrical resistivity and magnetoresistance (MR) measurements were carried out over the temperature range 4.2 K–300 K. The substitution of Ba results in the suppression of T IM , insulator-to-metal transition temperature. A low temperature upturn of resistivity is seen in all the samples of the system, which is attributed to the spin-glass-like transition. The conduction mechanism above T IM is explained by Mott variable range hopping (VRH) mechanism. The variation of MR with temperature and applied magnetic field is discussed. From the temperature dependent MR curves, it is observed that the large MR values are present over a wide temperature range and the maximum MR values occur at [Formula: see text]. The x=0.4 sample exhibits ~31% of MR with the application of a mere 0.4 T field at 5 K, which accounts for ~35% enhancement of MR of parent compound (~23% of MR% at 0.4 T at 5 K). The MR — H data is fitted to the power law ρ = ρ0-αHn, and it is found that the low temperature MR varies as square root of the applied magnetic field, as expected in conventional metals.

Spin splitting of one-dimensional subbands in high quality quantum wires at zero magnetic field

2000 ◽  
Vol 62 (23) ◽  
pp. 15842-15850 ◽  
Author(s):  
K. S. Pyshkin ◽  
C. J. B. Ford ◽  
R. H. Harrell ◽  
M. Pepper ◽  
E. H. Linfield ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Quantum Wires ◽  
Spin Splitting ◽  
Zero Magnetic Field ◽  
High Quality ◽  
One Dimensional

scholarly journals Spin depolarization in quantum wires polarized spontaneously in zero magnetic field

2004 ◽  
Vol 70 (15) ◽  
Author(s):  
N. T. Bagraev ◽  
I. A. Shelykh ◽  
V. K. Ivanov ◽  
L. E. Klyachkin
Keyword(s):  
Magnetic Field ◽  
Quantum Wires ◽  
Zero Magnetic Field ◽  
Spin Depolarization

Large Magnetoresistance at Room Temperature in Organic Semiconductor Sandwich Devices

2005 ◽  
Vol 871 ◽  
Author(s):  
Govindarajan Veeraraghavan ◽  
Omer Mermer ◽  
Thomas Lee Francis ◽  
Yugang Sheng ◽  
Tho Duc Nguyen ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Film Thickness ◽  
Organic Semiconductors ◽  
Applied Magnetic Field ◽  
Room Temperature ◽  
Electrode Materials ◽  
Bulk Material ◽  
Temperature Dependent ◽  
Semiconducting Polymer ◽  
Mr Effect

AbstractWe describe a recently discovered magnetoresistance (MR) effect in semiconducting polymer and small molecule sandwich devices. The MR effect reaches up to 10% in a magnetic field of 10mT at room temperature. This MR effect is therefore amongst the largest of any bulk material. We characterize this effect and discuss its dependence on voltage, film thickness, temperature, electrode materials and (unintentional) impurity concentration in three different organic semiconductors. We found that the MR effect is only weakly temperature dependent and does not depend on sign and direction of the applied magnetic field. To the best of our knowledge, the discovered MR effect is not adequately described by any of the mechanisms known to date.

scholarly journals Fabrication and Characterisation of Magnetorheological Shear Thickening Fluids

2020 ◽  
Vol 7 ◽  
Author(s):  
Vladimir Sokolovski ◽  
Tongfei Tian ◽  
Jie Ding ◽  
Weihua Li
Keyword(s):  
Magnetic Field ◽  
Shear Rate ◽  
Magnetic Fields ◽  
Applied Magnetic Field ◽  
Iron Concentration ◽  
Shear Thickening ◽  
Zero Magnetic Field ◽  
Iron Particles ◽  
Shear Thickening Fluid ◽  
Iron Concentrations

In this article, a magnetorheological shear thickening fluid (MRSTF) was fabricated based on magnetorheological (MR) material and shear thickening fluid (STF). The STF was firstly fabricated as the liquid phase, and carbonyl iron particles were then mixed with the prefabricated STF to synthesise a series of MRSTFs with various iron concentrations. Then, a rheometer was used to measure their viscosities by varying the shear rate under various magnetic fields. Both static and dynamic tests were conducted to study the rheology of MRSTFs under different magnetic fields. The tested results revealed that the MRSTF showed shear thickening under zero magnetic field and MR effect with increasing applied magnetic field. It was also noted that the viscosity of the MRSTFs can be controlled by both shear rate and the applied magnetic field. The concentration of iron particles played an important role in the MRSTFs’ rheological properties. The MRSTFs with higher iron particle concentrations revealed lower shear thickening effects but higher MR effects, which means the MRSTF with higher iron concentration can be treated as an effective MR fluid. Meanwhile, the MRSTF with low iron concentration displays good shear thickening effect under weak magnetic field. To summarise the behavior of MRSTFs with various iron concentrations and under different magnetic fields, three regions were proposed to provide guidelines to design MRSTFs and assist in their applications.

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