© 2026 Aqora Quantum S.A.S.

Terms Privacy Legal Notice

arXiv:2512.01415

Field-free diode effects in one-dimensional superconductor: a complex interplay between Fulde-Ferrell pairing and altermagnetism

SVS Sai Ruthvik, Tanay Nag

cond-mat.mes-hallquant-phSubmitted Dec 1, 2025• Announced Dec 2, 2025

Abstract

We investigate the emergence of nonreciprocal dissipationless supercurrents in one-dimension manifested through the superconducting diode effect (SDE) and the Josephson diode effect (JDE) in the absence of any external magnetic field, where inversion symmetry (IS) and time-reversal symmetry (TRS) can be intrinsically broken by spin-orbit coupling (SOC), and altermagnetism (AM), respectively. We investigate Ising and Rashba SOC separately in two models where two-component AM, assembled with crystallographic angle, can lead to qualitatively similar indirect band-gap closing and non-reciprocal supercurrent in a Fulde-Ferrell (FF) superconductor. Interestingly, in the absence of the above SOCs, SDE persists and the sign of efficiency can be altered by tuning the angle only. Parallel spin components with complementary momentum functions, ensuring the breaking of IS and TRS, can induce SDE in the presence of FF pairing. Continuing the analysis in the context of JDE, we explore the interplay between SOCs and AM with the p-wave and Fulde-Ferrell superconductivity in three different setups. The bulk bands contributes to the non-reciprocity in the case of p-wave superconductivity while JDE is dominated by Andreev bound states for FF superconductivity. Importantly, JDE continues to exist due to finite momentum Cooper pair even without AM and SOC unlike the p-wave superconductivity. The sign of JD efficiency can be tuned with angle for p-wave superconductivity while absence of such sign reversal is a hallmark signature of FF superconductivity. Similar to SDE, parallel spin components in conjunction with p-wave superconductivity can lead to JDE that can also be mediated by only FF pairing in the absence of SOC and AM.

Comments: 18 pages and 16 figures

Related papers

Many-body Josephson diode effect in superconducting quantum interferometers

Zelei Zhang, Jianxiong Zhai, Yi Zhang +1 more

We propose a many-body mechanism for a strong Josephson diode effect (JDE) in an interacting nanoscale SQUID formed by two parallel quantum dots coupled to superconducting leads. Unlike conventional diode behavior, where nonreciprocity originates from a skewed current-phase relation within a single, continuously evolving ground state, the JDE reported here is \emph{branch selected}: the positive and negative critical currents are optimized on different many-body branches across the $0$-$π$ phase boundary, yielding a substantial enhancement of the diode efficiency. We further show that a \emph{nonlocal} Cooper-pair tunneling channel, which binds the two electrons on different arms, is essential: it reshapes the $0$-$π$ boundary and produces a pronounced ``diode band'' in parameter space, in sharp contrast to the fragile hotspot obtained when only local Cooper-pair transfer is available. While the key physics is captured by an effective model in the superconducting atomic limit, our conclusions remain robust for realistic finite-gap devices, as demonstrated within a generalized atomic-limit framework.

arXiv:2603.25558•Mar 26, 2026•0 citations

Altermagnetism-driven FFLO superconductivity in finite-filling 2D lattices

Xia-Ji Liu, Hui Hu

We systematically investigate the emergence of finite-momentum Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconductivity in a square lattice Hubbard model with finite filling, driven by either $$d_{xy}$$ -wave or $$d_{x^{2}-y^{2}}$$ -wave altermagnetic order in the presence of on-site $$s$$ -wave attractive interactions. Our study combines mean-field calculation in the superconducting phase with pairing instability analysis of the normal state, incorporating the next-nearest-neighbor hopping in the single-particle dispersion relation. We demonstrate that the two types of altermagnetism have markedly different impacts on the stabilization of FFLO states. Specifically, $$d_{xy}$$ -wave altermagnetism supports FFLO superconductivity over a broad parameter regime at low fillings, whereas $$d_{x^{2}-y^{2}}$$ -wave altermagnetism only induces FFLO pairing in a narrow range at high fillings. Furthermore, we find that the presence of a Van Hove singularity in the density of states tends to suppress FFLO superconductivity. These findings may provide guidance for experimental exploration of altermagnetism-induced FFLO states in real materials with more complex electronic structures.

arXiv:2601.06735•AAPPS bulletin•May 6, 2026•4 citations

From Traveling Waves to Synthetic Gauge Fields: A Field-Free Route to Superconducting Diode Effect

Latu Kalita, Koustav Roy, Bilal Tanatar +1 more

The superconducting diode effect requires the forward and reverse bias currents to differ, a scenario achieved via inversion and time-reversal symmetries broken together. The latter, and the more crucial one, is inevitably achieved by a magnetic field. Here, we show that a spatio-temporally driven chemical potential of the form, $μ_j(t)=μ+V\cos(ωt+\kd j)$, achieves both at once. Applied to a helical Shiba chain, the drive transmutes a traveling Peierls phase via generating an odd-in-momentum term, equivalent to an imaginary next-nearest-neighbour Haldane-like hopping in real space. Remarkably, the protocol is spin-blind, which renders the time-reversal breaking via a synthetic gauge flux rather than an effective Zeeman field. The rectification is odd in the drive wavevector, with exact zeros at $\kd=nπ$ and an analytical optimum at $\kd=2π/3$. It is however, even in the exchange coupling, $J$ and persists even at $J=0$. Furthermore, the rectification scales inversely with the pair-breaking gap, yielding approximately $50\%$ rectification in the topological phase and $10\%$ in the trivial phase. Symmetry breaking is thus drive-controlled, allowing it to be switched on, tuned, and reversed without an external magnetic field.

cond-mat.mes-hallCross-listedarXiv:2610.29865•Oct 22, 2026

Fate of a strongly correlated d -wave superconductor in a Zeeman field: The Fulde-Ferrel-Larkin-Ovchinnikov perspective

Anushree Datta, Kun Yang, Amit Ghosal

The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase is an unconventional superconducting state found under the influence of a strong Zeeman field. This phase is identified by finite center-of-mass momenta in the Cooper pairs, causing the pairing amplitude to oscillate in real space. Repulsive correlations, on the other hand, smear out spatial inhomogeneities in $d$-wave superconductors. We investigate the FFLO state in a strongly correlated $d$-wave superconductor within a consolidated framework of Hartree-Fock-Bogoliubov theory and the Gutzwiller approximation. We find that the crucial effects of strong correlations lie in shifting the BCS-FFLO phase boundary towards a lower Zeeman field and thereby enlarging the window of the FFLO phase. In the FFLO state, our calculation features a sharp midgap peak in the density of states, indicating the formation of strongly localized Andreev bound states. We also find that the signatures of the FFLO phase survive even in the presence of an additional translational-symmetry-breaking competing order in the ground state. This is demonstrated by considering a broken-symmetry ground state with a simultaneous presence of the $d$-wave superconducting order and a spin-density wave order, often found in unconventional superconductors.

arXiv:1902.02758•Physical review. B./Physical review. B•Jul 16, 2019•6 citations

On the Fulde–Ferrell State in Spatially Isotropic Superconductors

Yoji Ohashi

Effects of superconducting fluctuations on the Fulde-Ferrell (FF) state are discussed in a spatially isotropic three-dimensional superconductor under a magnetic field. For this system, Shimahara recently showed that within the phenomenological Ginzburg-Landau theory, the long-range order of the FF state is suppressed by the phase fluctuation of the superconducting order parameter. [H. Shimahara: J. Phys. Soc. Jpn. {\bf 67} (1998) 1872, Physica B {\bf 259-261} (1999) 492] In this letter, we investigate this instability of the FF state against superconducting fluctuations from the microscopic viewpoint, employing the theory developed by Noziéres and Schmitt-Rink in the BCS-BEC crossover field. Besides the absence of the second-order phase transition associated with the FF state, we show that even if the pairing interaction is weak, the shift of the chemical potential from the Fermi energy due to the fluctuations is crucial near the critical magnetic field of the FF state obtained within the mean-field theory.

arXiv:cond-mat/0606369•Journal of the Physical Society of Japan•Nov 15, 2002•38 citations

Practical field-free superconducting diode for AC–DC rectification

Feng Li, Taichi Sato, Masamitsu Tanaka +1 more

We demonstrate a practical, field-free superconducting diode based on conventional Nb thin-film technology by integrating an intrinsic superconducting phase battery with an asymmetric DC superconducting quantum interference device. Unlike other approaches that require external magnetic fields or gate voltages to break time-reversal symmetry, our design achieves nonreciprocal supercurrents with on-chip phase bias, making it highly suitable for practical applications. The critical operational parameters, including the backward breakdown voltage and reverse resistance, are well defined by the Nb film gap voltage (∼2.8 mV) and the sub-gap resistance of the un-shunted Nb/Al–AlOx/Nb Josephson junctions. The resulting diode exhibits a forward supercurrent of 168 μA at 4.2 K, with a diode efficiency reaching 40%, a comprehensive performance exceeding prior field-free superconducting diodes. To validate its practicality, we fabricate and characterize a superconducting full-wave rectifier consisting of four such diodes. The demonstration of this rectifier highlights its potential as a DC source for superconducting digital circuits, paving the way for scalable, energy-efficient superconducting electronics.

Applied Physics Letters•Aug 18, 2025•1 citation

We investigate the emergence of nonreciprocal dissipationless supercurrents in one-dimension manifested through the superconducting diode effect (SDE) and the Josephson diode effect (JDE) in the absence of any external magnetic field, where inversion symmetry (IS) and time-reversal symmetry (TRS) can be intrinsically broken by spin-orbit coupling (SOC), and altermagnetism (AM), respectively. We investigate Ising and Rashba SOC separately in two models where two-component AM, assembled with crystallographic angle, can lead to qualitatively similar indirect band-gap closing and non-reciprocal supercurrent in a Fulde-Ferrell (FF) superconductor. Interestingly, in the absence of the above SOCs, SDE persists and the sign of efficiency can be altered by tuning the angle only. Parallel spin components with complementary momentum functions, ensuring the breaking of IS and TRS, can induce SDE in the presence of FF pairing. Continuing the analysis in the context of JDE, we explore the interplay between SOCs and AM with the p-wave and Fulde-Ferrell superconductivity in three different setups. The bulk bands contributes to the non-reciprocity in the case of p-wave superconductivity while JDE is dominated by Andreev bound states for FF superconductivity. Importantly, JDE continues to exist due to finite momentum Cooper pair even without AM and SOC unlike the p-wave superconductivity. The sign of JD efficiency can be tuned with angle for p-wave superconductivity while absence of such sign reversal is a hallmark signature of FF superconductivity. Similar to SDE, parallel spin components in conjunction with p-wave superconductivity can lead to JDE that can also be mediated by only FF pairing in the absence of SOC and AM.

We propose a many-body mechanism for a strong Josephson diode effect (JDE) in an interacting nanoscale SQUID formed by two parallel quantum dots coupled to superconducting leads. Unlike conventional diode behavior, where nonreciprocity originates from a skewed current-phase relation within a single, continuously evolving ground state, the JDE reported here is \emph{branch selected}: the positive and negative critical currents are optimized on different many-body branches across the

0

-

π

phase boundary, yielding a substantial enhancement of the diode efficiency. We further show that a \emph{nonlocal} Cooper-pair tunneling channel, which binds the two electrons on different arms, is essential: it reshapes the

0

-

π

boundary and produces a pronounced ``diode band'' in parameter space, in sharp contrast to the fragile hotspot obtained when only local Cooper-pair transfer is available. While the key physics is captured by an effective model in the superconducting atomic limit, our conclusions remain robust for realistic finite-gap devices, as demonstrated within a generalized atomic-limit framework.

We systematically investigate the emergence of finite-momentum Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconductivity in a square lattice Hubbard model with finite filling, driven by either

d_{xy}

-wave or

d_{x^{2}-y^{2}}

-wave altermagnetic order in the presence of on-site

s

-wave attractive interactions. Our study combines mean-field calculation in the superconducting phase with pairing instability analysis of the normal state, incorporating the next-nearest-neighbor hopping in the single-particle dispersion relation. We demonstrate that the two types of altermagnetism have markedly different impacts on the stabilization of FFLO states. Specifically,

d_{xy}

-wave altermagnetism supports FFLO superconductivity over a broad parameter regime at low fillings, whereas

d_{x^{2}-y^{2}}

-wave altermagnetism only induces FFLO pairing in a narrow range at high fillings. Furthermore, we find that the presence of a Van Hove singularity in the density of states tends to suppress FFLO superconductivity. These findings may provide guidance for experimental exploration of altermagnetism-induced FFLO states in real materials with more complex electronic structures.

The superconducting diode effect requires the forward and reverse bias currents to differ, a scenario achieved via inversion and time-reversal symmetries broken together. The latter, and the more crucial one, is inevitably achieved by a magnetic field. Here, we show that a spatio-temporally driven chemical potential of the form, $μ_j(t)=μ+V\cos(ωt+\kd j)$, achieves both at once. Applied to a helical Shiba chain, the drive transmutes a traveling Peierls phase via generating an odd-in-momentum term, equivalent to an imaginary next-nearest-neighbour Haldane-like hopping in real space. Remarkably, the protocol is spin-blind, which renders the time-reversal breaking via a synthetic gauge flux rather than an effective Zeeman field. The rectification is odd in the drive wavevector, with exact zeros at $\kd=nπ$ and an analytical optimum at $\kd=2π/3$. It is however, even in the exchange coupling,

J

and persists even at

J=0

. Furthermore, the rectification scales inversely with the pair-breaking gap, yielding approximately

50\%

rectification in the topological phase and

10\%

in the trivial phase. Symmetry breaking is thus drive-controlled, allowing it to be switched on, tuned, and reversed without an external magnetic field.

The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase is an unconventional superconducting state found under the influence of a strong Zeeman field. This phase is identified by finite center-of-mass momenta in the Cooper pairs, causing the pairing amplitude to oscillate in real space. Repulsive correlations, on the other hand, smear out spatial inhomogeneities in

d

-wave superconductors. We investigate the FFLO state in a strongly correlated

d

-wave superconductor within a consolidated framework of Hartree-Fock-Bogoliubov theory and the Gutzwiller approximation. We find that the crucial effects of strong correlations lie in shifting the BCS-FFLO phase boundary towards a lower Zeeman field and thereby enlarging the window of the FFLO phase. In the FFLO state, our calculation features a sharp midgap peak in the density of states, indicating the formation of strongly localized Andreev bound states. We also find that the signatures of the FFLO phase survive even in the presence of an additional translational-symmetry-breaking competing order in the ground state. This is demonstrated by considering a broken-symmetry ground state with a simultaneous presence of the

d

-wave superconducting order and a spin-density wave order, often found in unconventional superconductors.

Effects of superconducting fluctuations on the Fulde-Ferrell (FF) state are discussed in a spatially isotropic three-dimensional superconductor under a magnetic field. For this system, Shimahara recently showed that within the phenomenological Ginzburg-Landau theory, the long-range order of the FF state is suppressed by the phase fluctuation of the superconducting order parameter. [H. Shimahara: J. Phys. Soc. Jpn. {\bf 67} (1998) 1872, Physica B {\bf 259-261} (1999) 492] In this letter, we investigate this instability of the FF state against superconducting fluctuations from the microscopic viewpoint, employing the theory developed by Noziéres and Schmitt-Rink in the BCS-BEC crossover field. Besides the absence of the second-order phase transition associated with the FF state, we show that even if the pairing interaction is weak, the shift of the chemical potential from the Fermi energy due to the fluctuations is crucial near the critical magnetic field of the FF state obtained within the mean-field theory.

We demonstrate a practical, field-free superconducting diode based on conventional Nb thin-film technology by integrating an intrinsic superconducting phase battery with an asymmetric DC superconducting quantum interference device. Unlike other approaches that require external magnetic fields or gate voltages to break time-reversal symmetry, our design achieves nonreciprocal supercurrents with on-chip phase bias, making it highly suitable for practical applications. The critical operational parameters, including the backward breakdown voltage and reverse resistance, are well defined by the Nb film gap voltage (∼2.8 mV) and the sub-gap resistance of the un-shunted Nb/Al–AlOx/Nb Josephson junctions. The resulting diode exhibits a forward supercurrent of 168 μA at 4.2 K, with a diode efficiency reaching 40%, a comprehensive performance exceeding prior field-free superconducting diodes. To validate its practicality, we fabricate and characterize a superconducting full-wave rectifier consisting of four such diodes. The demonstration of this rectifier highlights its potential as a DC source for superconducting digital circuits, paving the way for scalable, energy-efficient superconducting electronics.