I am an assistant professor at the Department of Physics and Astronomy at Purdue University. Our group is interested in problems of theoretical physics at the intersection of quantum information science, condensed matter physics, and AMO physics. We also collaborate closely with experimental groups.
In particular, our group studies topological quantum materials such as topological insulators and quantum Hall states motivated by their use for topologically protected quantum computing. We are also interested in superconductor-semiconductor hybrids for conventional quantum computing.
We are looking for motivated students interested in theoretical quantum condensed matter physics for quantum information applications. Our group uses a mixture of analytical and numerical tools such as bosonization techniques, Green functions, conformal field theory, random matrix theory, exact diagonalization and DMRG.
2/10/2023 New preprint: Superconducting diode effect in quasi-one-dimensional systems. In this paper with Purdue grad student Tatiana de Picoli, REU student Zane Blood, and my Purdue colleague Yuli Lyanda-Geller, we introduce a theory of an intrinsic superconducting diode effect in quasi-1D systems, such as narrow wires. We find that confinement plays an important role in the diode "efficiency" -- there is an optimal wire width that maximizes the effect!
10/29/2022 New preprint: Topological symplectic Kondo effect. Kondo models with unitary [such as SU(2) of conventional magnetic impurities] and orthogonal symmetries [SO(M), which can be realized with Majorana modes] have been proposed in mesoscopic devices; the former in the late 1980s and the latter in early 2010s. Here we propose a mesoscopic device to realize a Kondo model of symplectic symmetry [Sp(2N)], "completing" the Kondo models of classical Lie algebras. The proposed device has the advantages that it does not require Majorana modes and can provide additional stability to the emergent anyons! This work was done with Purdue grad student Guangjie Li and Prof. Elio König from Max Planck Stuttgart.
7/20/2022 New preprint: Multichannel topological Kondo effect. In this paper, with Purdue grad student Guangjie Li and Yuval Oreg from Weizmann Institute of Science, we introduce a multichannel generalization to the so-called topological Kondo model. By considering the limit of large number of channels, we can move the low-temperature fixed point to weak coupling and study it perturbatively, which was not possible in the earlier "single-channel" version of the model. [Published version in Phys. Rev. Lett. and associated Purdue News story]
7/8/2022 New preprint: Supercurrent non-reciprocity and vortex formation in superconductor heterostructures. In this paper, with the experimental group of Leonid Rokhinson (grad student Ananthesh Sundaresh) and theorist Yuli Lyanda-Geller, we show experimentally and theoretically that the formation of Josephson vortices can lead to a "superconducting diode effect" in a superconducting heterostructure. [2/2023: Accepted in Nature Communications]
6/1/2022 Jukka receives the 2021 DEPSCoR award from the US Department of Defense! In close collaboration with Purdue experimentalist Leonid Rokhinson, the project aims at dispersive detection of charge state of a superconducting vortex and could be a measurement technique for future quantum computers.
12/8/2021 New preprint: Edge spin transport in disordered WTe2 two-dimensional topological insulator. It is quite well known that spin Hall conductance is not quantized in generic 2D topological insulators, due to non-conservation of spin current. In this paper, with Purdue undergrad Justin Copenhaver, we elucidate the conditions for breaking the conservation of spin current and quantify this with numerical simulations of spin conductance in disordered WTe2 topological insulator. [Published version in Phys. Rev. B]
6/7/2021 New preprint out on how to gap out edge neutral modes in quantum Hall systems: Gapping neutral modes in engineered quantum Hall edges. Neutral modes are semions which makes gap-opening perturbations rather different from the cases of fermions or bosons. For example, the analogue of BCS pairing involves a quartet of neutral modes. [Published version in Phys. Rev. B]
5/28/2021 Recent activity on super-semi hybrids and Coulomb blockade: 1. preprint experimenting different methods to probe an Andreev bound state (with Marcus group in Copenhagen), 2. our paper on Majorana signatures in Coulomb blockaded transport has been published in Physical Review B!
3/28/2021 Congratulations to Justin Copenhaver for being awarded the Barry Goldwater Scholarship! Justin is a Purdue undergraduate in the group and does research on topological insulators.
11/13/2020 Our paper on signatures of topological ground state degeneracy has been published in Physical Review Research!
10/13/2020 Our new preprint is out! We study theoretically sequential tunneling transport in a Majorana double island. This allows one to probe the interisland Majorana hybridization in dc and ac current.
8/1/2020 Website opening! Welcome!