Persistent currents circulate continuously without requiring external power sources. Here, we extend their theory to include dissipation within the framework of non-Hermitian quantum Hamiltonians. Using Green's function formalism, we introduce a non-Hermitian Fermi-Dirac distribution and derive an analytical expression for the persistent current that relies solely on the complex spectrum. We apply our formula to two dissipative models supporting persistent currents: (i) a phase-biased superconducting-normal-superconducting junction; (ii) a normal ring threaded by a magnetic flux. We show that the persistent currents in both systems exhibit no anomalies at any emergent exceptional points, whose signatures are only discernible in the current susceptibility. We validate our findings by exact diagonalization and extend them to account for finite temperatures and interaction effects. Our formalism offers a general framework for computing quantum many-body observables of non-Hermitian systems in equilibrium, with potential extensions to nonequilibrium scenarios.Persistent currents circulate continuously without requiring external power sources. Here, we extend their theory to include dissipation within the framework of non-Hermitian quantum Hamiltonians. Using Green's function formalism, we introduce a non-Hermitian Fermi-Dirac distribution and derive an analytical expression for the persistent current that relies solely on the complex spectrum. We apply our formula to two dissipative models supporting persistent currents: (i) a phase-biased superconducting-normal-superconducting junction; (ii) a normal ring threaded by a magnetic flux. We show that the persistent currents in both systems exhibit no anomalies at any emergent exceptional points, whose signatures are only discernible in the current susceptibility. We validate our findings by exact diagonalization and extend them to account for finite temperatures and interaction effects. Our formalism offers a general framework for computing quantum many-body observables of non-Hermitian systems in equilibrium, with potential extensions to nonequilibrium scenarios.

arXiv:2403.09569Physical Review LettersAug 23, 202432 citations

Supercurrents in Josephson junctions with chiral molecular potentials

Oleg Kuliashov, Alberto Cappellaro, Oded Millo +3 more

The influence of chiral molecular potentials on phase-coherent transport in superconducting Josephson junctions is investigated. Within a Bogoliubov--de Gennes tight-binding framework, a superconducting--normal--superconducting (SNS) junction functionalized by adsorbed chiral molecules is modeled, where electrostatic gradients generated by the molecules induce spin--orbit coupling in the normal region. The equilibrium charge current--phase relation is found to remain largely insensitive to molecular chirality in symmetric, zero-field configurations. In contrast, the spin-polarized equilibrium current exhibits a pronounced chirality-dependent response, with opposite enantiomers producing distinct and anisotropic spin-polarized Josephson currents. The resulting handedness contrast can be enhanced through control parameters such as molecular orientation and the strength of the induced spin--orbit coupling. The temperature dependence of these currents further shows that the chirality-dependent signatures persist across a range of temperatures well below the superconducting critical temperature. These results identify Josephson interferometry as a phase-sensitive setting for probing chirality-dependent spin structure and highlight spin-polarized superconducting transport as a controlled route toward integrating chiral molecular functionality into superconducting spintronic devices.The influence of chiral molecular potentials on phase-coherent transport in superconducting Josephson junctions is investigated. Within a Bogoliubov--de Gennes tight-binding framework, a superconducting--normal--superconducting (SNS) junction functionalized by adsorbed chiral molecules is modeled, where electrostatic gradients generated by the molecules induce spin--orbit coupling in the normal region. The equilibrium charge current--phase relation is found to remain largely insensitive to molecular chirality in symmetric, zero-field configurations. In contrast, the spin-polarized equilibrium current exhibits a pronounced chirality-dependent response, with opposite enantiomers producing distinct and anisotropic spin-polarized Josephson currents. The resulting handedness contrast can be enhanced through control parameters such as molecular orientation and the strength of the induced spin--orbit coupling. The temperature dependence of these currents further shows that the chirality-dependent signatures persist across a range of temperatures well below the superconducting critical temperature. These results identify Josephson interferometry as a phase-sensitive setting for probing chirality-dependent spin structure and highlight spin-polarized superconducting transport as a controlled route toward integrating chiral molecular functionality into superconducting spintronic devices.

cond-mat.supr-conCross-listedarXiv:2603.10925Mar 12, 2026

Stability of a superconductive atom chip with persistent current

Christoph Hufnagel, T. Mukai, Fujio Shimizu

The lifetime of $^{87}\text{R}\text{b}$ atoms trapped in a $\mathbsf{z}$ wire trap generated by a closed-circuit superconductive current on a ${\text{MgB}}_{2}$ strip is measured as a function of the distance between the atom and the strip. The lifetime is found to be longer than 10 s at a distance of $40\text{ }\ensuremath{\mu}\text{m}$. This value is an order of magnitude longer than the lifetime of a trap generated by a normal current at the same distance. However, it is many orders of magnitude shorter than the theoretical decay rate induced by the spin-flip transition caused by the fluctuation of the current. This shows that for a type-II superconductor the dominant trap loss mechanism is not the spin-flip transition caused by noise as with a normal current atom trap. An analysis of our measurement suggests that magnetic field distortion resulting from flux penetration into the superconductor leads to much faster decay.The lifetime of $^{87}\text{R}\text{b}$ atoms trapped in a $\mathbsf{z}$ wire trap generated by a closed-circuit superconductive current on a ${\text{MgB}}_{2}$ strip is measured as a function of the distance between the atom and the strip. The lifetime is found to be longer than 10 s at a distance of $40\text{ }\ensuremath{\mu}\text{m}$. This value is an order of magnitude longer than the lifetime of a trap generated by a normal current at the same distance. However, it is many orders of magnitude shorter than the theoretical decay rate induced by the spin-flip transition caused by the fluctuation of the current. This shows that for a type-II superconductor the dominant trap loss mechanism is not the spin-flip transition caused by noise as with a normal current atom trap. An analysis of our measurement suggests that magnetic field distortion resulting from flux penetration into the superconductor leads to much faster decay.

Physical Review AMay 29, 200932 citations

Strange behavior of persistent currents in small Hubbard rings

Santanu K. Maiti, Jayeeta Chowdhury, Samit Karmakar

arXiv:cond-mat/0310556Physics Letters AOct 21, 200431 citations

The lifetime of

^{87}\text{R}\text{b}

atoms trapped in a $\mathbsf{z}$ wire trap generated by a closed-circuit superconductive current on a

{\text{MgB}}_{2}

strip is measured as a function of the distance between the atom and the strip. The lifetime is found to be longer than 10 s at a distance of $40\text{ }\ensuremath{\mu}\text{m}$. This value is an order of magnitude longer than the lifetime of a trap generated by a normal current at the same distance. However, it is many orders of magnitude shorter than the theoretical decay rate induced by the spin-flip transition caused by the fluctuation of the current. This shows that for a type-II superconductor the dominant trap loss mechanism is not the spin-flip transition caused by noise as with a normal current atom trap. An analysis of our measurement suggests that magnetic field distortion resulting from flux penetration into the superconductor leads to much faster decay.