arXiv subjects

M. Dutta

Publications and source records attributed to M. Dutta.

3 recordsLinked to original sources

arXiv2014

Hysteresis in the Conductance of Asymmetrically Biased GaAs Quantum Point Contacts with in-plane Side Gates

We have observed hysteresis between the forward and reverse sweeps of a common mode bias applied to the two in-plane side gates of an asymmetrically biased GaAs quantum point contact. The size of the hysteresis loop increases with the amount of bias asymmetry between the two side gates and depends on the polarity of the bias asymmetry. It is argued that hysteresis may constitute another indirect proof of spontaneous spin polarization in the narrow portion of the quantum point contact.

cond-mat.mes-hall↗

arXiv2000

Applicability of Fermi golden rule and possibility of low-field runaway transport in nitrides

In order to justify applicability of the standard approach of perturbation theory for the description of transport phenomena in wide-band polar semiconductors with strong electron-phonon interactions, we have compared dependences of energy losses to the lattice on the electron drift velocity obtained for different materials in the frameworks of (a) a perturbative approach based on calculation of the scattering rates from Fermi's golden rule and (b) a non-perturbative approach based on the path-integral formalism of Thornber and Feynman. Our results reveal that despite strong electron-phonon coupling in GaN and AlN such that intercollision times become of the order of the period of phonon oscillation, standard perturbative treatment can still be applied successfully for this type of material. Our findings also indicate possibility for unique long-distance runaway transport in nitrides which may occur at the pre-threshold electric fields. Polaron ground state energy and effective masses are calculated for GaN and AlN as well as for GaAs and Al_2 O_3.

cond-mat↗

arXiv1996

Instability, Intermittency and Multiscaling in Discrete Growth Models of Kinetic Roughening

We show by numerical simulations that discretized versions of commonly studied continuum nonlinear growth equations (such as the Kardar-Parisi-Zhang equation and the Lai-Das Sarma equation) and related atomistic models of epitaxial growth have a generic instability in which isolated pillars (or grooves) on an otherwise flat interface grow in time when their height (or depth) exceeds a critical value. Depending on the details of the model, the instability found in the discretized version may or may not be present in the truly continuum growth equation, indicating that the behavior of discretized nonlinear growth equations may be very different from that of their continuum counterparts. This instability can be controlled either by the introduction of higher-order nonlinear terms with appropriate coefficients or by restricting the growth of pillars (or grooves) by other means. A number of such ``controlled instability'' models are studied by simulation. For appropriate choice of the parameters used for controlling the instability, these models exhibit intermittent behavior, characterized by multiexponent scaling of height fluctuations, over the time interval during which the instability is active. The behavior found in this regime is very similar to the ``turbulent'' behavior observed in recent simulations of several one- and two-dimensional atomistic models of epitaxial growth. [pacs{61.50.Cj, 68.55.Bd, 05.70.Ln, 64.60.Ht}]

cond-mat↗