Professor of Physics and Astronomy
Venkat Chandrasekhar's research interests lie in the fabrication, characterization and measurement of a wide variety of nanometer scale devices, with an emphasis on understanding how the small size of these devices affects their electrical and magnetic properties. A key element is investigating how different phenomena such as superconductivity and magnetism interact at these length scales. His group is currently focused on four main research areas:
The first area involves the study of quantum correlations in mesoscopic devices with normal-metal, superconducting and ferromagnetic elements. In particular, they are interested in measuring how interactions with a superconductor can lead to long-range coherent correlations between spatially separated electrons, with potential applications to quantum information.
The second area deals with investigating the properties of a novel class of synthesized complex oxide structures that combine ferromagnetic, ferroelectric and superconducting properties using electron-beam lithography and home-built low temperature scanning probe microscopes, including an atomic force microscope, a magnetic force microscope, and an electrostatic force microscope. While the focus here is on understanding the fundamental interactions between these sometimes competing phenomena, these new materials have significant potential as the basis for novel devices.
The goal of the third area of interest is to understand how size affects the dynamic magnetic properties of ferromagnets. Small ferromagnetic particles (or nanomagnets) behave differently than the large ferromagnetic films that form the basis of the current generation of magnetic storage media. In order to use these nanomagnets for the next generation of magnetic storage media, it is important to understand their dynamic magnetic properties. Our group's focus is on investigating the radiofrequency and microwave properties of arrays of nanomagnets.
The final and newest area of investigation is on the electrical and thermal properties of carbon nanotubes and graphene. Using a CVD furnace in our group, we are able to fabricate long, high-quality single-walled carbon nanotubes. These tubes are being used to make devices to study the potential of efficient thermal transport devices from carbon nanotubes. In addition, Chandrasekhar's group is making graphene devices using mechanical exfoliation, with the primary interest being the investigation of fundamental quantum phenomena.
Chandrasekhar's group interacts with the groups of Ketterson and Sauls in Physics, Lauhon, Dravid and Chang in Materials Science and Engineering, and with Grayson in EECS, as well as with local companies (NanoInk) and Argonne National Laboratory. He is also the Director of the new High Frequency Cryogenic Facility that is currently being set up at Northwestern with funding from the National Science Foundation.
A hybrid analog-digital phase-locked loop for frequency mode non-contact scanning probe microscopy, M.M. Mehta and V. Chandrasekhar, Rev. Sci. Instrum. 85, 013707 (2014). [pdf]
RTSPM: Real-time Linux control software for scanning probe microscopy, V. Chandrasekhar and M.M. Mehta, Rev. Sci. Instrum. 84, 013705 (2013).
Evidence for charge–vortex duality at the LaAlO3/SrTiO3 interface, M.M. Mehta, D.A. Dikin, C.W. Bark, S. Ryu, C.M. Folkman, C.B. Eom and V. Chandrasekhar, Nature Communications 3, 955 (2012).
Coherent nonlocal correlations in Andreev interferometers, P. Cadden-Zimansky, J. Wei, and V. Chandrasekhar, New J. Phys. 14 043004 (2012).
Positive noise cross-correlation in hybrid superconducting and normal-metal three-terminal devices, Jian Wei and Venkat Chandrasekhar, Nature Physics, Published online: 16 May 2010 | doi:10.1038/nphys1669.
dc and high frequency magnetic properties of nanopatterned CoFeO4 arrays fabricated using sol-gel precursors, Goutam Sheet, Alexandra R. Cunliffe, Erik J. Offerman, Chad M. Folkman, Chang-Beom Eom, and Venkat Chandrasekhar, J. App. Phys. 107, 104309 (2010).
Controllable Patterning and CVD Growth of Isolated Carbon Nanotubes with Direct Parallel Writing of Catalyst Using Dip-Pen Nanolithography, Irma Kuljanishvili, Dmitriy A. Dikin, Sergey Rozhok, Scott Mayle, and Venkat Chandrasekhar, Small 5, 2523 (2009).
Thermal transport in superconductor/normal-metal structures, Venkat Chandrasekhar, Superconducting Science and Technology 22, 083001 (2009).