TITLE : Seeing hidden Currents and exploring their behavior in Quantum Materials
ABSTRACT :
Electrical current is one of the most fundamental observables in condensed matter physics, yet directly visualising how it flows through quantum materials remains remarkably challenging. In many modern quantum systems—including topological insulators, correlated electron materials and superconductors—the current distribution contains valuable information about the underlying electronic states, often inaccessible through conventional electrical transport measurements alone. In this seminar, I will describe our efforts in my lab at IIT Kanpur to develop non-contact electrodynamic techniques capable of imaging and probing current flow with high sensitivity. Using magneto-optical imaging and inductive measurements, we directly visualise current distributions and investigate how charge transport evolves in a variety of quantum materials.
I will first discuss current imaging in topological insulators, where we directly observe the competition between surface and bulk conduction. I will then present our recent work on the topological Kondo insulator SmB₆, where non-contact electrodynamic measurements reveal evidence for a correlated low-temperature surface state that exhibits two-fluid-like behaviour beyond the conventional topological insulator picture. Time permitting, I will briefly illustrate how these experimental approaches are being extended to superconductors and other strongly correlated quantum materials, highlighting opportunities for developing new electrodynamic probes of quantum matter.
References:
[1] Sayantan Ghosh, Sugata Paul, Tamoghna Chattoraj, Amit Jash, Zachary Fisk and S. S. Banerjee*: Low Temperature Two Fluid State in SmB6, Phys. Rev. Materials.-Letters, 10 (4), L042001 (2026).
[2] Sayantan Ghosh, Sugata Paul, Amit Jash, Zachary Fisk and S. S. Banerjee*: Exploration of strongly correlated states in SmB6 through a comparison of its two-coil pick-up response to that of Bi2Se3, Phys. Rev. B 108, 205101 (2023)
[3] Amit Jash, Ankit Kumar, Sayanta Ghosh, A Bharathi, S. S. Banerjee*: Imaging current distribution in a topological insulator Bi2Se3 in the presence of competing surface and bulk contributions to conductivity, Scientific Reports 11, 7445 (2021)
[4] Amit Jash, Sayantan Ghosh, A. Bharathi, and S. S. Banerjee*: Coupling-decoupling of conducting topological surface states in thick Bi2Se3 single crystals, Physical Review B, 101, 165119 (2020)
[5] N Roy, S Ghosh, S Saha, GL Prajapati, R Dagar, DS Rana, S. S. Banerjee*:Imaging of current crowding effect across the metal to insulator transition in a thin film with thickness gradient, Physical Review B 105 (8),085143 (2022)
[6] Ankit Kumar, Amit Jash, Tsuyoshi Tamegai, S. S. Banerjee*:Imaging the effect of drive on the low-field vortex melting phenomenon in Ba0. 6K0. 4Fe2As2 single crystal, Physical Review B, 101,184516(2020)
ABOUT THE SPEAKER :
MEETING DETAILS :
Speaker: Prof. Satyajit Banerjee, Dept of Physics, IIT Kanpur
Venue: A1-NKN, South Campus, IIT Mandi
Date and Time: July 31, 2026, Friday at 4:00 pm