Professor Nandini Trivedi's Research
The Big
Picture
My area of research is theoretical condensed matter physics. The major
effort in this field is to understand how many degrees of
freedom—many particles for example—organise
themselves. What are the types of organizations or phases
that they
form? What new properties emerge in these phases that are not present
at the few particle level? Little at the atomic scale prepares us for
at this rich variety, such as the existence and properties of metals,
semiconductors, insulators, magnets, superconductors, and many more.
While particle physics and string theory aim to explore the physics of
the very small and astrophysics and cosmology the physics of the very
large, condensed matter physics is the fundamental physics of the
emergence of complexity from constituents or laws that at the
elementary level are simple.
Quantum
Monte Carlo Simulations of Strongly Interacting Bose and Fermi Atoms
Fermions in Optical Lattices
Normal state pseudogaps
We were the first to provide a credible and natural explanation for
gap-like features seen above Tc in the underdoped cuprates in terms of
precursor pairing correlations. We demonstrated that Fermi liquid
behavior in simple models of short coherence length
superconductors is explicitly violated between a new temperature scale
T* where the pairing amplitude builds up, which is larger than the Tc
at which phase coherence sets in. Our results are in remarkable qualitative agreement with density of
states, spin susceptibility and NMR relaxation rate experiments in the
pseudogap regime.
“Pairing
and Spin Gap in the Normal State of Short Coherence Length
Superconductors”, M. Randeria, N. Trivedi, A.
Moreo, and R. Scalettar, Phys. Rev. Lett. 69, 2001 (1992).
“Deviations
From Fermi-Liquid Behavior above Tc in 2D Short Coherence Length
Superconductors”, N. Trivedi and M. Randeria, Phys.
Rev. Lett. 75,
312 (1995).
“Pairing Correlations above Tc and Pseudogaps in Underdoped
Cuprates”,
M. Randeria and N. Trivedi, J. Phys. Chem. of Solids, 59, 1754 (1998).
High Tc Superconductivity
We have developed a
variational formulation of the strongly correlated superconducting
state that has given insight into a major puzzle about the cuprates:
the existence of two energy scales, the gap and Tc, with qualitatively
different doping dependences, quite unlike BCS theory. We show that
such behavior arises as a natural consequence of strong correlations
near a Mott insulator.
“Projected Wavefunctions and High Temperature Superconductivity”, Arun Paramekanti, Mohit Randeria and Nandini Trivedi, Phys. Rev. Lett. 87, 217002 (2001).
“High Tc superconductors: A Variational Theory of the Superconducting State”, A. Paramekanti, M. Randeria and N. Trivedi, Phys. Rev. B 70, 054504 (2004).
We have calculated the nontrivial doping dependences of the
superconducting order parameter, correlation length, momentum
distribution, nodal quasiparticle weights and dispersion, optical
spectral weight and superfluid density, previously thought to be not
possible within a variational approach. The remarkable quantitative
agreement of our results with experiments, and several new predictions,
have proved to be vital in the revival of interest in RVB wave
functions.
“The Physics Behind High-Temperature Superconducting Cuprates: The `Plain Vanilla’ Version Of RVB”,
P. W. Anderson, P. A. Lee, M. Randeria, T. M. Rice, N. Trivedi, and F.
C. Zhang; J. Phys. Cond. Mat. 16, R755–R769 (2004).
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