PHOTON-ASSISTED INTERSUBBAND TRANSITIONS IN A QUANTUM WIRE

NANO ◽  
2006 ◽  
Vol 01 (03) ◽  
pp. 213-218 ◽  
Author(s):  
MONICA GUDWANI ◽  
VINOD PRASAD ◽  
PRADEEP KUMAR JHA ◽  
MAN MOHAN

We investigate the response of electrons confined in a quantum wire in the presence of intense terahertz (THz) electric field. An exact and powerful nonperturbative fundamental approach of Floquet theory is employed to solve the equation of motion for resonantly driven intersubband transitions. Several interesting features namely dynamic Stark shift, power broadening and hole-burning are observed with the variation in electric field strength. In addition, the degeneracy between several excited states is found to be removed in the presence of high electric field.

2020 ◽  
Vol 95 (7) ◽  
pp. 075805
Author(s):  
S A Safwan ◽  
Nagwa El Meshad ◽  
Assma Saleh ◽  
Hekmat M Hassanein

1970 ◽  
Vol 25 (3) ◽  
pp. 406-411
Author(s):  
F. J. Comes ◽  
U. Wenning

Molecules in certain excited states can be forced to predissociate in an external electric field. This effect will be shown to occur with H2 and D2. The molecular dissociation is made possible by an altered coupling mechanism as compared to the mechanism considered for the Kronig's selection rules. The interaction is a linear function of the field strength. It is further demonstrated that also molecular fields (van der Waal's fields) may cause the effect which is shown by the collision induced predissociation of the excited molecular states under consideration


2016 ◽  
Vol 136 (10) ◽  
pp. 1420-1421
Author(s):  
Yusuke Tanaka ◽  
Yuji Nagaoka ◽  
Hyeon-Gu Jeon ◽  
Masaharu Fujii ◽  
Haruo Ihori

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
Swati Baruah ◽  
U. Sarma ◽  
R. Ganesh

Lane formation dynamics in externally driven pair-ion plasma (PIP) particles is studied in the presence of external magnetic field using Langevin dynamics (LD) simulation. The phase diagram obtained distinguishing the no-lane and lane states is systematically determined from a study of various Coulomb coupling parameter values. A peculiar lane formation-disintegration parameter space is identified; lane formation area extended to a wide range of Coulomb coupling parameter values is observed before disappearing to a mixed phase. The different phases are identified by calculating the order parameter. This and the critical parameters are calculated directly from LD simulation. The critical electric field strength value above which the lanes are formed distinctly is obtained, and it is observed that in the presence of the external magnetic field, the PIP system requires a higher value of the electric field strength to enter into the lane formation state than that in the absence of the magnetic field. We further find out the critical value of electric field frequency beyond which the system exhibits a transition back to the disordered state and this critical frequency is found as an increasing function of the electric field strength in the presence of an external magnetic field. The movement of the lanes is also observed in a direction perpendicular to that of the applied electric and magnetic field directions, which reveals the existence of the electric field drift in the system under study. We also use an oblique force field as the external driving force, both in the presence and absence of the external magnetic field. The application of this oblique force changes the orientation of the lane structures for different applied oblique angle values.


2020 ◽  
Vol 75 (11) ◽  
pp. 937-962
Author(s):  
Heinz-Jürgen Schmidt

AbstractWe consider the solution of the equation of motion of a classical/quantum spin subject to a monochromatical, elliptically polarized external field. The classical Rabi problem can be reduced to third-order differential equations with polynomial coefficients and hence solved in terms of power series in close analogy to the confluent Heun equation occurring for linear polarization. Application of Floquet theory yields physically interesting quantities like the quasienergy as a function of the problem’s parameters and expressions for the Bloch–Siegert shift of resonance frequencies. Various limit cases are thoroughly investigated.


Author(s):  
Dhaval Solanki ◽  
Zeynab Rezaee ◽  
Anirban Dutta ◽  
Uttama Lahiri

Abstract Background Investigation of lobule-specific electric field effects of cerebellar transcranial direct current stimulation (ctDCS) on overground gait performance has not been performed, so this study aimed to investigate the feasibility of two lobule-specific bilateral ctDCS montages to facilitate overground walking in chronic stroke. Methods Ten chronic post-stroke male subjects participated in this repeated-measure single-blind crossover study, where we evaluated the single-session effects of two bilateral ctDCS montages that applied 2 mA via 3.14 cm2 disc electrodes for 15 min targeting (a) dentate nuclei (also, anterior and posterior lobes), and (b) lower-limb representations (lobules VIIb-IX). A two-sided Wilcoxon rank-sum test was performed at a 5% significance level on the percent normalized change measures in the overground gait performance. Partial least squares regression (PLSR) analysis was performed on the quantitative gait parameters as response variables to the mean lobular electric field strength as the predictors. Clinical assessments were performed with the Ten-Meter walk test (TMWT), Timed Up & Go (TUG), and the Berg Balance Scale based on minimal clinically important differences (MCID). Results The ctDCS montage specific effect was found significant using a two-sided Wilcoxon rank-sum test at a 5% significance level for 'Step Time Affected Leg' (p = 0.0257) and '%Stance Time Unaffected Leg' (p = 0.0376). The changes in the quantitative gait parameters were found to be correlated to the mean electric field strength in the lobules based on PLSR analysis (R2 statistic = 0.6574). Here, the mean electric field strength at the cerebellar lobules, Vermis VIIIb, Ipsi-lesional IX, Vermis IX, Ipsi-lesional X, had the most loading and were positively related to the 'Step Time Affected Leg' and '%Stance Time Unaffected Leg,' and negatively related to the '%Swing Time Unaffected Leg,' '%Single Support Time Affected Leg.' Clinical assessments found similar improvement in the TMWT (MCID: 0.10 m/s), TUG (MCID: 8 s), and BBS score (MCID: 12.5 points) for both the ctDCS montages. Conclusion Our feasibility study found an association between the lobular mean electric field strength and the changes in the quantitative gait parameters following a single ctDCS session in chronic stroke. Both the ctDCS montages improved the clinical outcome measures that should be investigated with a larger sample size for clinical validation. Trial registration: Being retrospectively registered.


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