Publications

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• Tunable quantum transport in flux-driven designer rings: Role of hopping dimerization, electron filling, and phase architecture

  Souvik Roy, Ranjini Bhattacharya

  SciPost Phys. Core 8, 090 (2025) · published 8 December 2025 | Toggle abstract · pdf

  We explore quantum transport in a one-dimensional Su-Schrieffer-Heeger (SSH) ring threaded by an Aharonov-Bohm flux, incorporating a quasiperiodic site potential based on a generalized cosine modulation with both primary and secondary components. Focusing on spinful, non-interacting electrons, we analyze persistent current behavior across a broad range of filling factors, Aubry-André-Harper (AAH) phase shifts, and hopping dimerizations. Our results uncover a rich interplay of localization-delocalization transitions, driven by the secondary modulation strength, leading to highly tunable and non-monotonic transport signatures. Persistent current is markedly enhanced near the symmetric hopping regime, where quantum interference dominates. In spin-imbalanced configurations, we identify regimes exhibiting pure spin current without net charge flow, suggesting potential for dissipationless spintronic functionalities. To the best of our knowledge, this is the first systematic study to examine quantum transport in such a flux-threaded SSH ring with dual-component quasiperiodic modulations, unifying re-entrant localization, spin-current generation, current stabilization, and phase-selective control. The inverse and normalized participation ratios, together with the state-resolved current, reveal the interplay between eigenstate localization and transport, providing insight into the microscopic mechanisms underlying current suppression and enhancement. For completeness, we also present the system-size dependence of the current. These findings position the quasiperiodic SSH ring as a versatile platform for realizing controllable quantum interference and spin-resolved transport in low-dimensional systems.

• Annual modulation of dark matter signals: Experimental results and new ideas

  Felix Kahlhoefer

  SciPost Phys. Proc. 12, 004 (2023) · published 3 July 2023 | Toggle abstract · pdf

  Direct detection experiments searching for the scattering of dark matter particles off nuclei expect an annual modulation in their event rate. In this presentation, I will review the theoretical predictions and the experimental status of the search for annual modulations, with a focus on ongoing and planned experiments using NaI detectors. In particular, I will discuss the interpretation of the DAMA signal and related model-building efforts.

• MEG final results and progress towards MEG II

  Toshiyuki Iwamoto on behalf of the MEG II collaboration

  SciPost Phys. Proc. 1, 040 (2019) · published 21 February 2019 | Toggle abstract · pdf

  The MEG experiment, which is to search for lepton flavor violating muon decay, had been successfully finished in 2013. The final sensitivity of the experiment was 5.3 × 10−13, and since the experiment did not find any signal, the upper limit of the branching ratio of the μ+ → e+γ was set to be 4.2 × 10−13 at 90% CL. The MEG II experiment will improve the sensitivity by an order of magnitude with three years data taking, and the target sensitivity is 6×10−14. In 2018 after the detector integration, the muon beam data taking will be planned with limited number of readout channels. In 2019, the engineering run and the physics run will be started.

• Solar neutrino physics with Borexino

  Andrea Pocar, M. Agostini, K. Altenmüller, S. Appel, V. Atroshchenko, Z. Bagdasarian, D. Basilico, G. Bellini, J. Benziger, G. Bonfini, D. Bravo, B. Caccianiga, F. Calaprice, A. Caminata, L. Cappelli, S. Caprioli, M. Carlini, P. Cavalcante, F. Cavanna, A. Chepurnov, K. Choi, L. Collica, D. D’Angelo, S. Davini, A. Derbin, X. F. Ding, A. Di Ludovico, L. Di Noto, I. Drachnev, K. Fomenko, A. Formozov, D. Franco, F. Gabriele, C. Galbiati, M. Gschwender, C. Ghiano, M. Giammarchi, A. Goretti, M. Gromov, D. Guffanti, T. Houdy, E. Hungerford, Aldo Ianni, Andrea Ianni, A. Jany, D. Jeschke, S. Kumaran, V. Kobychev, G. Korga, T. Lachenmaier, M. Laubenstein, E. Litvinovich, P. Lombardi, L. Ludhova, G. Lukyanchenko, L. Lukyanchenko, I. Machulin, G. Manuzio, S. Marcocci, J. Maricic, J. Martyn, E. Meroni, M. Meyer, L. Miramonti, M. Misiaszek, V. Muratova, B. Neumair, M. Nieslony, L. Oberauer, V. Orekhov, F. Ortica, M. Pallavicini, L. Papp, Ö. Penek, L. Pietrofaccia, N. Pilipenko, A. Porcelli, G. Raikov, G. Ranucci, A. Razeto, A. Re, M. Redchuk, A. Romani, N. Rossi, S. Rottenanger, S. Schönert, D. Semenov, M. Skorokhvatov, O. Smirnov, A. Sotnikov, L. F. F. Stokes, Y. Suvorov , R. Tartaglia, G. Testera, J. Thurn, E. Unzhakov, A. Vishneva, R. B. Vogelaar, F. von Feilitzsch, S. Weinz, M. Wojcik, M. Wurm, O. Zaimidoroga, S. Zavatarelli, K. Zuber, G. Zuzel

  SciPost Phys. Proc. 1, 025 (2019) · published 20 February 2019 | Toggle abstract · pdf

  We present the most recent solar neutrino results from the Borexino experiment at the Gran Sasso underground laboratory. In particular, refined measurements of all neutrinos produced in the {\it pp} fusion chain have been made. It is the first time that the same detector measures the entire range of solar neutrinos at once. These new data weakly favor a high-metallicity Sun. Prospects for measuring CNO solar neutrinos are also discussed.

• Light sterile neutrinos: a critical overview

  Ivan Esteban

  SciPost Phys. Proc. 1, 026 (2019) · published 20 February 2019 | Toggle abstract · pdf

  Light sterile neutrinos, first proposed after the results of the LSND experiment, have been a polemical topic for the last decades after seemingly contradictory data appeared from different experiments. In this overview, I review the experimental hints that point towards sterile neutrinos as well as their statistical compatibility. Even though the muon neutrino disappearance experiments strongly rule out vanilla sterile neutrinos, each oscillation channel remains internally mostly consistent. In any case, in the near future a series of independent and precise experiments should finally settle down this issue.

• Recent results from reactor antineutrino experiments

  Hyunkwan Seo

  SciPost Phys. Proc. 1, 027 (2019) · published 20 February 2019 | Toggle abstract · pdf

  The smallest neutrino mixing angle $\theta_{13}$ has been successfully measured by the disappearance of reactor antineutrinos at RENO, Daya Bay, and Double Chooz. The oscillation frequency is also measured based on energy and baseline dependent disappearance probability of reactor antineutrinos. Recent results fi nd a variation in the observed reactor antineutrino flux as a function of the reactor fuel evolution. We report more precisely measured values of $\theta_{13}$ and $\Delta m^2_{ee}$ and results on the evolution of observed reactor antineutrino yield and spectrum.

• Reference measurements for indirect dark matter searches with p+C collisions at the NA61/SHINE experiment

  Michał Naskręt on behalf of the NA61/SHINE Collaboration

  SciPost Phys. Proc. 12, 068 (2023) · published 5 July 2023 | Toggle abstract · pdf

  NA61/SHINE is a large-acceptance fixed-target experiment located at the CERN SPS, which studies final hadronic states in interactions of various particles and nuclei. It is unique in terms of providing data on a variety of collision systems at different collision energies. This allows for wide deuteron, antiproton and antideuteron production cross-section studies. The latter are currently considered a possible dark matter interaction signal with exceptionally small background. The measurements on carbon targets are important to reduce systematic experimental effects due to experiment-internal antideuteron production, as the most abundant element in the path of an incoming particle for the AMS-02 experiment is carbon. This manuscript will focus on analysis of NA61/SHINE data on p+C thin target collisions in the context of light (anti)nuclei production. A preliminary analysis of experimental data and the particle identification method as well as current deuteron and antideuteron yields will be described.

• Spectral solutions for the Schrödinger equation with a regular singularity

  Pushkar Mohile, Ayaz Ahmed, T. R. Vishnu, Pichai Ramadevi

  SciPost Phys. Core 7, 041 (2024) · published 5 July 2024 | Toggle abstract · pdf

  We propose a modification in the Bethe-like ansatz to reproduce the hydrogen atom spectrum and the wave functions. Such a proposal provided a clue to attempt the exact quantization condition (EQC) for the quantum periods associated with potentials $V(x)$ which are of the form $(V(x) = |x| + a/|x| + b/|x|^2 )$. We validate the EQC proposal by showing that our computed Voros spectrum in the limit $a,b → 0$ is matching well with the true spectrum of the familiar $|x|$ potential. Thus we have given a route to obtain the spectral solution for the one dimensional Schrödinger equation involving potentials with regular singularity at the origin.

• A brief note on the G$_2$ Affleck-Kennedy-Lieb-Tasaki chain

  Hosho Katsura, Dirk Schuricht

  SciPost Phys. Core 8, 052 (2025) · published 15 August 2025 | Toggle abstract · pdf

  We consider the valence bond solid (VBS) state built of singlet pairs of fundamental representations and projected onto adjoint representations of the exceptional Lie group G$_2$. The two-point correlation function in the VBS state is non-vanishing only for nearest neighbours, but possesses finite string order. We construct a parent Hamiltonian for the VBS state, which constitutes the G$_2$ analog of the famous AKLT chain.

• Impurity effect and vortex cluster phase in mesoscopic type-1.5 superconductors

  Tian-Yi Han, Guo Wang, Jie Li, Hai Huang

  SciPost Phys. 19, 140 (2025) · published 28 November 2025 | Toggle abstract · pdf

  Based on two-band time-dependent Ginzburg-Landau theory, we study the electromagnetic properties of two-band mesoscopic superconductors. We perform the numerical simulations with the finite element method, and determine the minimum sample size $L_c$ for the existence of the type-1.5 superconductivity from the obtained phase diagram in the absence of impurity. Meanwhile in the presence of an isotropic impurity, our numerical results reveal that the vortex cluster state induced by the attractive defect potential will gradually appear in the mesoscopic system with the sample size $L < L_c$, and the critical defect strength is about 0.2 in the $T_c$ disorder model. In addition, we also investigate the effect of anisotropic defect structures and multiple correlated disorders on the patterns of magnetic vortex distributions. Our theoretical study thus indicates that the diversity of impurity depositions has a significant influence on the semi-Meissner state in mesoscopic type-1.5 superconductors.