Publications
Peer-reviewed work across graphene, Kagome lattices, topology, spectroscopy, and correlated quantum phases.
7 publications
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2026
Symmetry Origins of the Field-Free Superconducting Diode Effect in the Kagome Superconductor CsV3Sb5
Abstract
Field-free superconducting diode effects require both inversion-symmetry breaking and an internal time-reversal-symmetry (TRS) breaking field, making them sensitive probes of hidden order in superconductors. In centrosymmetric kagome AV3Sb5, inversion symmetry should generally preclude the observation of the superconducting diode effect. Furthermore, though TRS breaking has been reported in the superconducting regime of CsV3Sb5, whether it is generated by superconductivity or inherited from charge-density-wave (CDW) order remains unresolved. Here we show that pristine CsV3Sb5 devices exhibit no intrinsic field-free superconducting diode effect, whereas surface oxidation or asymmetric etching activates a large nonreciprocal supercurrent. Moreover, the response is stochastic, with sweep-dependent polarity and magnitude, indicating metastable TRS-breaking domain configurations. Small out-of-plane magnetic fields stabilize the superconducting diode response, consistent with field selection of such domains. Finally, when long-range CDW order is suppressed by Ti doping, the SDE disappears. Our results establish the symmetry requirements for the field-free SDE in CsV3Sb5, reveal its stochastic domain-controlled character, and link superconducting-state TRS breaking to CDW-related order.
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2026
Large Field-Free Superconducting Diode Effect with Nonmonotonic Polarity Reversals in NbSe2/CrBr3 Heterostructures
Abstract
The superconducting diode effect (SDE), characterized by nonreciprocal dissipationless supercurrent, offers a promising route toward ultralow-power superconducting electronics. Yet most realizations require an external magnetic field, and achieving a large, controllable SDE at zero field remains challenging. Here we report a field-free SDE with an efficiency reaching 35.7% in a van der Waals NbSe2/CrBr3 heterostructure, whose polarity is programmable by magnetic-field history. Unlike conventional mechanisms based on finite-momentum pairing, the SDE originates from the leading symmetry-allowed cubic term odd in Cooper-pair momentum, which yields unequal critical currents while leaving the equilibrium condensate at zero momentum. Remarkably, upon sweeping a perpendicular magnetic field, the diode polarity undergoes nonmonotonic and hysteretic reversals that cannot be explained by Meissner screening or conventional ferromagnetic proximity. Combining transport measurements, micromagnetic simulations, and a generalized Ginzburg-Landau theory, we attribute these unconventional behaviors to layered ferrimagnetism in CrBr3, where coexisting ferromagnetic and antiferromagnetic interlayer couplings produce a history-dependent interfacial exchange field acting on NbSe2. Our results reveal a distinct mechanism for nonreciprocal superconductivity and establish layered van der Waals magnetism as a versatile platform for high-efficiency, programmable, field-free superconducting diodes.
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2026
Unconventional hysteresis due to time-reversal symmetry breaking superconductivity in RbV3Sb5
Abstract
The study of kagome materials has recently attracted much attention due to the presence of many electron-electron interaction-driven phases in a single material. In this work, we report time-reversal symmetry-breaking superconductivity in the thin-flake kagome material RbV3Sb5. Firstly, when an in-plane magnetic field is swept in opposite directions, we observe an unconventional form of hysteresis in magnetoresistance, which is different from the hysteresis induced by extrinsic mechanisms. In contrast, no such hysteresis is observed in CsV3Sb5 samples below their superconducting transition temperature. Strikingly, at a fixed magnetic field, the finite-resistance state in RbV3Sb5 can be transitioned into the superconducting state by applying and subsequently removing a large current. Secondly, at temperatures around 400 mK, the re-entrance of superconductivity occurs during an in-plane field-sweeping process with a fixed sweeping direction. The observations of the unconventional hysteresis and re-entrance suggest the existence of time-reversal symmetry-breaking superconducting states in RbV3Sb5.
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2025
Switchable half-quantum flux states in a ring of the kagome superconductor CsV3Sb5
Abstract
Magnetic flux quantization in units of Phi0 = h/2e is a defining feature of superconductivity, rooted in the charge-2e nature of Cooper pairs. In a ring geometry, the flux quantization leads to oscillations in the critical temperature with magnetic flux, known as the Little-Parks effect. While the maximal critical temperature is conventionally at zero flux, departures from this rule, for instance shifts by a half-quantum flux Phi0/2, clearly signal unconventional superconducting states and require sign-changing order parameters. Historically, such pi-phase shifts in Little-Parks oscillations have been found in tricrystals or engineered ring structures that intentionally incorporate a pi-phase shift. Here we report the discovery of switchable half-quantum flux states in rings made from single crystals of the kagome superconductor CsV3Sb5. We observe Little-Parks oscillations with a pi-phase shift at zero bias current, which can be reversibly tuned to conventional Little-Parks oscillations upon applying a bias current. Between the pi-phase and 0-phase regimes, h/4e periodic oscillations appear. Our observations suggest unconventional pairing, potentially in the form of a multicomponent order parameter in the kagome superconductor CsV3Sb5, and reveal an electrically tunable landscape of competing superconducting condensates and fractional flux states.
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2025
Tunable Anomalous Hall Effect in Non-Magnetic Topological Semimetal Cd3As2 Nanoplates
Abstract
The emergence of topology has profoundly transformed condensed matter physics, driving the discovery of topological materials, including topological semimetals. Here, we report the observation of gate-tunable anomalous Hall effect (AHE) in the non-magnetic Dirac semimetal Cd3As2. The anomalous Hall conductivity reaches the maximum when the gate voltage is near the Dirac point. Fitting the anomalous Hall resistivity using the scaling relationship of AHE reveals that the AHE in Cd3As2 is dominated by the intrinsic contribution of Berry curvature. Our results are valuable for understanding AHE in topological semimetals and could have possible potential applications in topological devices.
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2025
Pseudo-spin-polarized topological superconductivity in kagome RbV3Sb5
Abstract
Kagome superconductors AV3Sb5 (A = K, Rb, Cs) have sparked considerable interest due to the presence of several intertwined symmetry-breaking phases within a single material. Interestingly, in a recent experiment, magnetic hysteresis was observed in the superconducting state through magnetoresistance measurements in RbV3Sb5 (Nature Communications 17, 1310, 2026), providing strong evidence of a spontaneous time-reversal symmetry-breaking superconducting state. The magnetic hysteresis, combined with crystalline symmetry, imposes strong constraints on the possible pairing symmetries of the superconducting state. In this work, we propose that RbV3Sb5 is a nodal topological superconductor with pseudo-spin-polarized Cooper pairs. The pseudo-spin-polarized superconducting domains resemble the properties of ferromagnetic domains and induce hysteresis. Moreover, the nodal topological superconducting state possesses Majorana flat-band modes at the sample boundary, which can be detected by tunneling experiments.
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2024
Two-fold symmetric superconductivity in the Kagome superconductor RbV3Sb5
Abstract
The recently discovered kagome superconductors offer a promising platform for investigating intertwined orders and novel states, including topology, superconductivity, charge density waves, and more. The interplay among these orders can spontaneously break rotational symmetry, giving rise to exotic phenomena such as nematicity or even nematic superconductivity. Here we present our findings on the two-fold symmetric superconductivity in thin-flake RbV3Sb5 in response to direction-dependent in-plane magnetic fields, in contrast to the inherent six-fold structural symmetry of the crystal lattice. The two-fold symmetry was evidenced through a combination of magnetoresistance transport experiments, critical magnetic field measurements, and observations of anisotropic superconducting gaps. Additionally, by altering the experimental configuration, we also detected the presence of six-fold symmetric components superimposed on the two-fold symmetry at the boundary between normal and superconducting states. Our results underscore the correlation-driven symmetry-breaking phenomena and emphasize the potential of this correlated kagome family as a promising platform for investigating intertwined orders, including unconventional superconductivity.