Staff Directory

Our Team

Describe your team here.

  • Srijan Deoraj
  • Raquel Queiroz
  • Peter Ding

    I'm a graduate student, and my focus is understanding how disorder affects topological phenomena. In our research, we're looking at how Landau levels react to disorder that keeps certain symmetries intact, like chiral symmetry. Interestingly, the zeroth Landau level of a Dirac particle stays strong even when faced with chiral disorder. This resilience is connected to a math concept called an index theorem of elliptical differential operators. We're working to apply this idea to different real-world situations. Our first application involves studying two-dimensional transition metal dichalcogenides, comparing them to graphene. We're also exploring twisted bilayer graphene's Moire potential to understand the implications of the index theorem.

    In another aspect of our research, we're looking at disorder-induced phase transitions in topological systems. In the quantum Hall system, we observe critical delocalized states that separate different quantum Hall plateaus due to both disorder and topology. The variety of topological materials nowadays adds an interesting layer to studying these transitions. Depending on a material's symmetry class and its specific topological features, we see different critical behaviors, such as multifractal critical states or even a whole critical phase.

  • Nishchhal Verma

    Background:
    Ph.D. Physics, Ohio State University 2017-22;
    B.S. M.S. Physics, IISER Kolkata, India 2012-17


    Research Interests:
    Topological Phenomenon in Quantum Matter

  • Kiril Kolevski
  • Julian Ingham

    I’m a graduate student working in theoretical condensed matter physics, specialising in unconventional superconductivity and topological matter. My recent work is investigating the role disorder plays in the transport properties of topological materials, but I also work on several more long-standing research themes.

    One key research direction lies in the study of kagome metals. Recent interest in quasi-two-dimensional metallic kagome systems, instigated with the study of Fe3Sn2, has undergone a crescendo with the discovery of the superconducting compounds AV3Sb5 (A=Rb,K,Cs), notable for the rich series of electronic phase transitions in the normal state above Tc. A number of interesting features of the AV3Sb5 family remain to be further explored: the materials appear to exhibit multiple superconducting phases as a function of doping and pressure, extreme sensitivity to applied strain and fields, and smectic ordering coexisting with quasi-one-dimensional excitations. Additionally, the materials are highly exfoliable and can be reduced to the few-layer limit. In parallel, an ongoing deluge of experiments continue to report the discovery of new kagome metals, including 166 compounds such as ScV6Sn6, and the titanium-based 135 family ATi3Bi5 (A=Cs,Rb), which as yet remain less thoroughly studied.

    A second focus is on moiré heterostructures. By stacking two layers and aligning them with a relative twist, the resulting structure has a different periodicity to the individual layers, forming an effective lattice with a larger periodicity known as a moiré superlattice. The field of `twistronics' - the study of heterostructures of twisted two-dimensional materials - was initiated with the spectacular discovery of superconductivity and correlated insulators in magic angle twisted bilayer graphene, two layers of graphene twisted by an angle at which the bandwidth is drastically reduced. I am interested in studying the nature of correlated phases which appear in these systems as well as their response to various perturbations, such as proximity-induced spin-orbit coupling.

    Online Talks:

    “Quadratic Dirac fermions and the competition of ordered states in twisted bilayer graphene”, Virtual Science Forum https://www.youtube.com/watch?v=Ac6-U-aef4U.

    “Excitonic order and the puzzle of time-reversal-symmetry in kagome metals“, Rice Quantum Matter Seminar https://www.youtube.com/watch?v=EB1OOTYQuX0.

    Selected publications:

    "Chiral excitonic order from twofold van Hove singularities in kagome metals”, Nature Communications 14, 605 (2023).

    “Quadratic Dirac fermions and the competition of ordered states in twisted bilayer graphene”, arXiv:2308.00748 [cond-mat.str-el].

     

  • Harshitra Mahalingam
  • Daniel Muñoz-Segovia

    I am a postdoctoral researcher working in theory of condensed matter physics. In general, I am interested in the effects of correlations, topology and disorder in electron systems, and the interesting phases arising from their interplay. While my research is theoretical, trying to understand the phenomenology found in experiments is an important source of motivation behind several of my works.

    I did my PhD at the Donostia International Physics Center in Spain, where I studied correlated phases in transition metal dichalcogenides and topological phases in amorphous materials. In particular, we have predicted doping-induced nematic and stripe charge density wave (CDW) transitions in TiSe2, which might explain the apparently contradictory experimental observations of its symmetry. Based on the signatures of subleading unconventional superconductivity, we have also studied the collective mode spectrum of NbSe2, proposing a Leggett mode to explain the STM experiments. Finally, we have also introduced the structural spillage, a novel efficient topological indicator applicable to noncrystalline systems.

    My current research follows on from my previous investigations, and also combines several of the above topics. A promising research line deals with moiré heterostructures, where the interplay between correlations, topology and disorder becomes crucial to explain the rich phase diagrams. Information about these exotic phases might be revealed in their collective mode spectrum, such as charge and spin collective modes, which might be experimentally accessible by local techniques coupling to the relevant degrees of freedom.

    Another interesting avenue is the study of superconductivity and topology in disordered and amorphous systems. On the one hand, topological wavefunctions might exhibit interesting critical properties when disorder is added, which might enhance the superconducting critical temperature. On the other hand, I am interested in analyzing the possibility of realizing topological superconductivity in amorphous systems, where Anderson’s theorem might be overcome by the local order present in a family of these systems.

    Online talks:

    Selected publications:

  • Carolina Paiva
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