Profile
Educational Background
Ph.D., Physics, University of California, Los Angeles, 2003
M. Sc, Physics, Indian Institute of Technology, Kanpur, India, 1997
Research Interests
Condensed matter theory, Majorana fermions and topological quantum computation, physics of high-temperature superconductors, cold atom systems in optical traps and lattices:
Majorana fermions and topological quantum computation: We are interested in topological superconducting (TS) states to realize Majorana fermion (MF) quasiparticles in the order parameter defects of systems with strong spin-orbit (SO) interactions for use in quantum computation. MFs, which were introduced in high energy physics by the Italian physicist E. Majorana more than seven decades ago, have recently made a decisive and convincing comeback to condensed matter physics in part due to the efforts of my work and those of my collaborators in the last few years. The TS states I focus on support a certain kind of unusual zero energy quantum states in various order parameter defects which satisfy the Majorana condition. The Majorana condition is at the heart of non-Abelian quantum statistics and, as proposed by Kitaev, can potentially serve as building blocks for a topological quantum computer. In this sense, this research is intimately connected to research in quantum computation. In past works, I proposed schemes for realizing TS states and MFs in semiconductor heterostructures spurring leading experimental groups worldwide to experimentally look for MF excitations in the proposed systems. This body of work has given rise to a new sub-field - TS states in spin-orbit coupled semiconductor heterostructures - and has recently seen a great flurry of activities.
Cuprate high-temperature superconductivity: In my Ph. D work we helped develop the theory and phenomenology of the d-density wave state (DDW, a version of the staggered flux state) applicable to the underdoped regime of the cuprates. I have been able to explain many exciting experimental results in the framework of the DDW theory of the pseudogap phase. These include pronounced Nernst and other thermoelectric effects, diamagnetism, aspects of the neutron scattering, and the polar Kerr effect (an indication of broken time-reversal symmetry) above T_c in the underdoped regime of the cuprates. I plan on exploring aspects of the DDW state such as the collective mode spectrum and the neutron scattering signatures in the pseudogap regime of the cuprates. Additionally, we will also consider other candidate phases for the pseudogap regime which are close in energy with the DDW state. These include the electronic nematic state, charge density wave state, and the loop current state within the CuO unit cell without broken translational symmetry. We will focus on the magnetic excitation spectrum of these states that follows from their collective mode spectrum and compare it with the neutron scattering experiments. These states will also be investigated with regard to their Fermi surface topology, the quantum oscillation signatures of the Fermi surfaces, and the diamagnetic response/Nernst effect, as well as their transport signatures in the pseudogap phase.
Cold atom systems in optical traps and lattices: Past experimental breakthrough at NIST realizing spin-orbit coupling for ultra-cold atoms opened exciting new possibilities for the observation of novel topological superfluid phases in cold atomic systems. In these systems, I wrote the very first paper on using an artificially generated spin-orbit coupling, Zeeman field, and s-wave superfluid interactions to create topological superfluid states and MFs (this paper, Physical Review Letters 101, 160401 (2008), in fact, had the genesis of the idea that was later applied to the condensed matter systems to propose Majorana fermions in semiconductor-superconductor heterostructures). We will continue to develop concrete schemes for realizing TS states and the associated topological phase transitions using experimental techniques which have already been realized. These include spin-orbit coupling in 1D systems, photoemission spectroscopy, etc.
With the important techniques already developed, the realization of topological physics in cold atomic systems now seems tantalizingly close to experimental reach. Note, however, that in the cold fermion systems with a Feshbach resonance, the superfluidity is interaction-generated (rather than proximity induced as in the proposals for condensed matter systems). This implies that, even at zero temperature, one needs weak coupling among various 1D chains to stabilize BCS superfluid states. Whether or not the MFs at the chain ends survive such weak couplings among the chains is an important open question that will be addressed in the framework of chiral symmetry. In addition, we will address various methods for the actual observation/demonstration of nontrivial excitations such as MFs in degenerate Fermi gases. More generally we will be interested in the BCS-BEC crossover physics in the spin-orbit coupled degenerate Fermi gases in all dimensions. In recent work, we showed that in 3D systems the Rashba-type spin-orbit coupling allows the observation of a so-called 3D Weyl superfluid phase on the BCS side of the phase diagram. The Weyl phase is separated from the regular s-wave superfluid phase by a topological phase transition. An interesting question we will investigate involves the thermodynamic signatures of such a topological superfluid transition that are measurable in the cold atom experiments.
Research Group (Lab)
Current graduate students: Binayyak Roy, Srimayi Korrapati; Past graduate students and postdocs: Eugene Dumitrescu (ORNL), Girish Sharma (IIT, Mandi), Chuanchang Zeng (Beijing Academy of Quantum Information), Christopher Moore, Kangjun Seo
Selected Publications
Five selected recent publications:
(1) Jay Sau, Sumanta Tewari, “From Majorana fermions to topological quantum computation in semiconductor/superconductor heterostructures”,
Book Chapter “ Topological Insulator and Related Topics”, Ed. L. Li and K. Sun, Elsevier (2021); arXiv: 2105.03769
(2) S. Nandy, Chuanchang Zhang, Sumanta Tewari, “Chiral anomaly induced nonlinear Hall effect in multi-Weyl semimetals”, Phys. Rev. B 104, 205124 (2021)
(3) G. Sharma, S. Nandy, K. V. Raman, S. Tewari, “Revisiting magnetotransport in Weyl semimetals”, arXiv:2201.09922
(4) S. Tewari, T. D. Stanescu, “Majorana fermions go for a ride”, Perspective Article, Science 367, Issue 6473 pp 23 (2019); https://doi.org/10.1126/science.aaz6961
(5) C. Moore, Chuanchang Zeng, T. D. Stanescu, Sumanta Tewari, “Quantized zero bias conductance plateau in semiconductor-superconductor heterostructures without non-Abelian Majorana zero modes” Phys. Rev. B 98, 155314 (2018)
Memberships
American Physical Society
Honors and Awards
Grant Awards from DARPA, NSF, ARO, ONR
Links
Google Scholar Page
My comments on quantum realms and particles carried by Marvel Comicbook
arXiv e-print page
