arXiv subjects

Jin-Xing Hou

Publications and source records attributed to Jin-Xing Hou.

8 recordsLinked to original sources

arXiv2026

Nonreciprocal Superconducting Transport from Chiral Edge States

Nonreciprocal superconducting transport enables dissipationless rectification and has attracted considerable interest, yet its microscopic origin is typically sought in bulk electronic states. Here, we show that boundary-controlled chiral edge states in topological systems provide a simple yet largely overlooked mechanism for nonreciprocal superconducting transport. Focusing on chiral kagome antiferromagnets, we demonstrate that out-of-plane spin canting or spin-orbit coupling opens a high-Chern-number bulk gap, giving rise to multiple chiral edge modes. Strikingly, sublattice-dependent boundary termination selects a single-valley character for the edge states, leading to asymmetric edge spectra at opposite edges. This boundary asymmetry directly yields observable nonreciprocal signatures in Josephson junctions oriented transverse to the edges, including asymmetric Andreev spectra, Josephson diode effect, and anomalous Fraunhofer interference patterns. These findings broaden the microscopic understanding of superconducting nonreciprocity and highlight boundary engineering as a tunable route toward superconducting diode devices.

cond-mat.supr-con↗

arXiv2026

Enhancement of Josephson Supercurrent in a $π$-Junction state by Chiral Antiferromagnetism

Magnetic order typically disrupts superconductivity, reducing the supercurrent. Here, we show that chiral antiferromagnetism, with non-relativistic spin-split bands and distinctive valley-locked spin texture, can instead significantly enhance Josephson supercurrents. This enhancement stems from the emergence of dominant equal-spin triplet pairing and strong fluctuations of singlet pairing in momentum space, both induced by chiral antiferromagnetism. We demonstrate these results in Josephson junctions composed of chiral antiferromagnetic metals and conventional superconductors on kagome lattices. Furthermore, we show that the enhanced Josephson supercurrent is stabilized in a $π$-junction state. These phenomena persist across a broad energy range and remain stable for different temperatures and junction lengths. Our results unveil a previously unexplored mechanism for enhancing supercurrent by strong magnetic order and provide crucial insights into the large Josephson currents observed in Mn$_3$Ge.

cond-mat.supr-con↗

arXiv2026

Altermagnetic Even-Odd Effects in CsV$_2$Te$_2$O Josephson Junctions

The interplay between conventional superconductivity and unconventional magnetism offers an exciting platform for realizing exotic superconducting phenomena. Here, we investigate Josephson effects in planar and vertical junctions based on CsV$_2$Te$_2$O-family materials, which host hidden $d$-wave altermagnetism with G-type antiferromagnetic order. In monolayer-based planar junctions, the quasi-1D, nearly flat, spin-polarized bands of the altermagnet, when coupled to $s$-wave superconductors, produce a \textit{fully} spin-polarized supercurrent with strong directional anisotropy -- a spin-selective Josephson effect. In multilayers, we uncover an \textit{altermagnetic even-odd effect}: spin-polarized supercurrents persist only in odd-layer planar junctions but cancel exactly in even layers. Thus, layer parity acts as a switch for spin-polarized supercurrent. In vertical junctions, odd-layer barriers enhance equal-spin triplet transport while even layers favor opposite-spin transport, yielding a robust period-two oscillation in the total supercurrent with layer number. These layer-parity-dependent responses represent a general even-odd effect in hidden altermagnets, applicable to diverse magnetic and transport phenomena.

cond-mat.supr-con↗

arXiv2025

Field-free Josephson diode and tunable $ϕ_0$-junction in chiral kagome antiferromagnets

The recent realization of superconducting proximity effect in chiral antiferromagnets (cAFMs) opens a new route to nonreciprocal superconducting transport of fundamental interest and practical importance. Using microscopic modeling and symmetry analysis, we show that Josephson junctions formed by conventional $s$-wave superconductors (SCs) and cAFMs on the kagome lattice exhibit Josephson diode effects and anomalous phase shifts ($ϕ_0$-junction state) when space inversion $\mathcal{I}$, time-reversal $\mathcal{T}$, and combined mirror-time-reversal $\mathcal{TM}_z$ symmetries are simultaneously broken. We propose two setups to realize these phenomena and achieve high diode efficiency. (i) An SC/cAFM/SC junction with spin-orbit coupling, which enables a field-free diode effect with a robust tunable $ϕ_0$-junction state. (ii) An SC/cAFM/cAFM$^\prime$/SC junction, where two cAFM layers with different in-plane order orientations, under an out-of-plane Zeeman exchange field, produces significant diode effect and anomalous phase shifts. These results establish a direct link between $\mathcal{TM}_z$ symmetry breaking and nonreciprocal superconductivity, suggesting cAFMs as versatile platforms for symmetry-engineered Josephson diodes and tunable $ϕ_0$-junctions.

cond-mat.supr-con↗

arXiv2025

Spin-Polarized Josephson Supercurrent in Nodeless Altermagnets

Long-range propagation of equal-spin triplet Cooper pairs typically occurs in ferromagnet/$s$-wave superconductor junctions, where net magnetization plays a crucial role. Here, we propose a fundamentally different scenario in which Josephson supercurrents mediated exclusively by spin-triplet pairings emerge in systems with \textit{zero} net magnetization. We identify collinear altermagnets, particularly a subclass termed nodeless altermagnets, as ideal platforms to realize this phenomenon. These materials host spin-split Fermi surfaces that do not intersect altermagnetic nodal lines and support maximal spin-valley polarization, yielding fully spin-polarized electronic states at each valley. Consequently, Josephson junctions based on nodeless altermagnets sustain supercurrents solely through spin-polarized triplet pairing correlations, simultaneously contributed by spin-up Cooper pairs from one valley and spin-down Cooper pairs from the other. Furthermore, controlling the relative local inversion-symmetry breaking at the two interfaces enables a robust 0--$π$ transition without fine tuning, while adjusting the junction orientation allows a crossover between pure triplet and mixed singlet-triplet states. Our work thus establishes nodeless altermagnets as a unique platform for altermagnetic superconductors with magnetization-free spin-polarized supercurrents.

cond-mat.supr-con↗

arXiv2024

Embedded Majorana Islands

Mesoscopic superconducting islands hosting Majorana zero modes (MZMs), or Majorana islands in short, offer a prototype of topological qubits. In this work we investigate theoretically the model of a generic Majorana island tunneling-coupled to a single-piece metallic substrate, hence an \textit{embedded Majorana island}. We show the crucial consequences of an interplay between the topological ground states nonlocally addressed by the MZMs and the metallic bath with coherent electron propagation: on the one hand, the topological degeneracy on the Majorana island can be preserved, by virtue of the particle-hole symmetry, despite the apparent bath-induced coupling between MZMs; on the other hand, the electronic interference in the metallic bath may lead to profound alterations to the renormalization group behavior of the hybrid system towards low energy/temperature compared with conventional Kondo physics. This work serves to establish the model of embedded Majorana islands as an experimentally relevant and theoretically intriguing problem particularly in the direction of topological quantum computation.

cond-mat.mes-hall↗

arXiv2017

The Geometric Structure of Quantum Resources for Bell-diagonal states

Two-qubit Bell-diagonal states can be depicted as a tetrahedron in three dimensions. We investigate the structure of quantum resources, including coherence and quantum discord, in the tetrahedron. The ordering of different resources measures is a common problem in resource theories, and which measure should be chosen to investigate the structure of resources is still an open question. We consider the structure of quantum resources which is not affected by the choice of measure. Our work provides a complete structure of coherence and quantum discord for Bell-diagonal states. The pictorial approach also indicates how to explore the structure of resources even when we don't have consistent measure of a concrete quantum resource.

quant-ph↗

arXiv2017

The role of coherence during classical and quantum decoherence

The total correlations in a bipartite quantum system are measured by the quantum mutual information $\mathcal{I}$, which consists of quantum discord and classical correlation. However, recent results in quantum information shows that coherence, which is a part of total correlation, is more general and more fundamental than discord. The role of coherence in quantum resource theories is worthwhile to investigate. We first study the relation between quantum discord and coherence by reducing the difference between them. And then, we consider the dynamics of quantum discord, classical correlations and quantum coherence under incoherent quantum channels. We discover that coherence indicate the behavior of quantum discord (classical correlation) for times $t<\bar t$, and indicate the decoherence of classical correlation (quantum discord) for times $t>\bar t$. What is more, the coherence frozen and decay indicate the quantum discord and classical correlation frozen and decay respectively.

quant-ph↗