Random matrix theory:Disordered nanostructures like quantum wires pose a challenge to the way we normally think of a macroscopic object. It is not enough to understand the `average' properties of various observables in such a system, because often the distributions are so broad that just the mean or the variance fails to provide any meaningful description of the system. Understanding various novel phenomena associated with such broad distributions in electronic transport properties as well as developing theoretical tools to describe their surprising universality is one of my long-term interests. One powerful tool in understanding the universal features in disparate physical systems is the application of random matrix theory. Understanding the implications of the original Wigner-Dyson ensembles and the Dorokhov-Mello-Pereyra-Kumar equation for transport in disordered conductors as well as their generalizations to include aspects of metal-insulator transitions and criticality has been one of the recurrent themes. Recent interests include the so-called Muttalib-Borodin ensemble and its generalizations. [See e.g. publications 15-18, 20-32, 34-36, 38-40, 43, 45, 47-49, 53-56, 59, 65-67, 69, 73, 76, 88]
Thermoelectricity:While the idea of generating electricity from a temperature difference has been known for a long time and has been pursued vigorously from a technological point of view, it turns out that non-linear effects in nanowires have been overlooked, where devices with high efficiency and large power output are found to be possible in principle. Practical applications require nanowires with high electrical but low thermal conductivity and the effects of surface disorder has been shown to be important. An exact mapping of the surface disorder to a smooth wire with additional phonon interactions has proved useful to understand the broad features of thermal conduction seen experimentally in silicon nanowires. [See e.g. publications 75, 79, 81, 84, 85, 87]
Electron transport in disordered magnets:Understanding the temperature and disorder dependence of the longitudinal as well as the (anomalous) Hall conductivities in thin ferromagnetic as well as antiferromagnetic films can in principle provide quantitative estimates of the spin dependent transport coefficients in magnetic materials. From a fundamental point of view, this will provide insights into the role of spin in transport phenomena. From a technological point of view, this could be important in the context of device technology based on spintronics. In particular, weak localization effects in anomalous Hall effect have been found to be important. [See e.g. publications 57, 58, 60, 64, 68, 70, 71, 77, 78]
Exact solutions of Ising systems:Exact solutions of toy models often provide insights that are useful for more complicated realistic systems. Studies of simple magnetic systems have shown that the two-dimensional Ising antiferromagnetic interactions can lead to distinctly different disordered ground states. The usual Ising antiferromagnet with only pair interactions lead to a highly degenerate frustrated ground state, while the Ising model with only triplet interactions lead to a less degenerate disordered ground state but with no frustration. The difference shows up in magnetic susceptibility. This has led to a useful quantitative description of frustration in disordered systems. In addition, exact solutions of Ising systems with both pair and triplet interactions in a magnetic field has provided interesting magnetic field induced transitions in two-dimensional ferromagnetic systems. [See e.g publications 46, 61, 72, 82, 86]
Geometric frustration and long range order in molecular solids:This is a collaboration with N. Sullivan's experimental group studying the effects of geometrical frustration on orientational ordering in molecular solids. The group (with J. Hamida and S. Pilla) has observed strong memory and aging effects in pure solid nitrogen, induced by a very small ac electric field in the audio frequency range. Understanding the origin of such effects and their consequences is an important goal. [See e.g. publications 37, 41, 42, 44, 50, 51, 62, 63, 80, 83]
Superconductivity and other correlated electron systems:Superconductivity has been of great interest for a variety of reasons. Earlier interests include universal effects of non-magnetic impurities on the transition temperature as well as the upper critical field. Other interests involve strongly disordered systems and Bohm-Aharonov effects with half-flux quanta. [See e.g. publications 2-4, 6-8, 10-14, 19, 33, 74]
Surface diffusion:Surface diffusion of adatoms play important role in determining the properties of surfaces. In particular phonon-adatom interactions lead to concentration dependent diffusion coefficients. [See publications 5, 9]
Collaborators:A. Abbout, S. Abhinav, K. Alam, P.W. Anderson, B. Andraka, Y. Avishai, J.H. Barry, C. Blecken, D. Bowman, D. Browne, S. Buvaev, J.P. Carinin, Y. Chen, J. Choi, L. Coffey, T. Costi, A. Douglas, V.J. Emery, S.B. Field, G. Fleury, A. Garcia-Martin, E. Genio, S. Ghosh, R. Gomer, V. Gopar, K.E. Gray, J. Hamida, A. Hebard, S. Hershfield, P.J. Hirschfeld, M.E.H. Ismail, R.T. Kampwirth, J. Klauder, V.E. Kravtsov, J. Kroha, K. Levin, P. Markos, P. Mello, P. Mitra, R. Misra, S.R. Nagel, T. Nakayama, B.J. Nartowt, V.N. Nicopoulos, P. Ostrovsky, J-L. Pichard, S. Pilla, T.V. Ramakrishnan, T.B. Rosenbaum, J.P. Sethna, K. Slevin, A.D. Stone, N. Sullivan, Y. Takano, T. Tanaka, M. Tringides, H. Tsujii, D. Wang, P. Woelfle, S. Yadav. K. A. Muttalib / muttalib@phys.ufl.edu / Last modified: Jan, 2020 |