Prof. Kumar's Homepage

Pradeep Kumar

Emeritus Professor

Department of Physics
PO Box 118440
University of Florida
Gainesville FL, 32611-8440 
New Physics Building (NPB2160)

(352) 672-1931 phone
(352) 392-5339 Fax
(352) 392-8754 Prog. Assist.

I am affiliated with the National High Magnetic Field Laboratory as well as with the Institute for Fundamental Theory 

My research interests are in the field of condensed matter theory.  The current activities are in the area of (the numbers refer to the papers in the list of publications):

Metamagnetism (112, 113, 114, 116, 117):   Metamagnetism  refers to a discontinous change in the magnetization at a critical field Bc.  It happens at low temperatures and is associated with a peak in the temperature dependence of the low field linear susceptibility.  Shivaram et al discovered that nonlinear susceptibilities also contained peaks in their temperature dependence which scales with the critical field.  One could say that in spite of the complex electronic structure  of the materials involved, there is really only one energy scale that dominates metamagnetic behavior.  A model built with a single energy scale shows many of the observed features.  There are thermodynamic identities that help understand several different experimental results.

Multiferroics  (107, 110, 111, 115):  Maxwell was the first to note that in vacuum, a coupling between electric and magnetic fields is possible only at a finite frequency and wave vector.  Thus came the electromagnetic waves.  In a material there are exceptions and interesting consequences.  One finds a magnetoelectric effect (a magnetization caused by a magnetic field or an electric dipole moment  arising from a magnetic field) under special conditions. 

Higher Order Phase Transition:  Was Ehrenfest right ? (79, 85, 90, 92,  97, 102,  104): Until the early 1930's, all thermodynamic phase transitions were supposed to involve a latent heat and a change in density (or some equivalent observable).  What we now call a first order phase transition.  Paul Ehrenfest came across two transitions, superconductivity in metals and superfluidity in Helium where there was no latent heat and no change in density, instead there was a change in specific heat and compressibility.  He built a thermodynamic framework to describe those transitions as second order phase transitions and thereby opening door to yet higher order phenomena.  Landau's description based on broken symmetry and the expansion of the free energy provided an alternative framwork.  That has been misunderstood to conclude that there is something wrong with the Ehrenfest picture.  Ehrenfest was entirely correct.

Are there phase transitions of order infinity?