Interplay of Competing Quantum Phases in Layered Superconductors: A Multi-Technique Study

Date

Apr 16, 2025

Time

11:00 AM - 12:00 PM

Speaker

Vahid Sazgari Ardakani

Affiliation

Paul Scherrer Institut Villigen

Language

en

Main Topic

Materialien

Host

Rita Taubert

Description

Understanding the tunability and interplay between various quantum states such as superconductivity, charge order, magnetic order, and anomalous transport phenomena in complex quantum materials is central to condensed matter physics. These intertwined phases not only challenge our fundamental understanding of electron correlations but also offer pathways for engineering novel quantum functionalities [1, 2, 3]. In this seminar, I will present a multi-technique investigation employing muon spin rotation (µSR) and transport measurements, combined with uniaxial strain and hydrostatic pressure, to explore competing electronic orders in two distinct layered superconductors. Our study on 6R-TaS2 reveals a competition among charge density wave (CDW), superconductivity, and a hidden order phase associated with an anomalous Hall effect and large magnetoresistance [4]. Under hydrostatic pressure, the CDW order is progressively suppressed, with its onset temperature reduced by 50% at 2 GPa, while superconductivity is enhanced—transitioning from a nodal to a nodeless pairing state with increasing superfluid density. Notably, the hidden order phase is highly sensitive to external perturbations indicating its fragile nature compared to the CDW state. The suppression of both CDW and hidden order frees electronic states, reinforcing superconductivity. Similarly, uniaxial strain experiments on La2−xBaxCuO4 [5] reveal an anisotropic response: c-axis compression suppresses 3D superconductivity while preserving spin-stripe order, whereas in-plane stress enhances superconductivity and destabilizes stripe order [5, 6]. This underscores the critical role of crystallographic anisotropy in governing quantum phase competition in cuprates. These findings highlight the intricate balance between superconductivity, charge order, and emergent electronic phases in strongly correlated materials. Moreover, they demonstrate how external tuning parameters—pressure and strain—can be leveraged to manipulate competing orders, offering new insights into unconventional superconductivity and the broader design principles for quantum materials. References [1] Z. Guguchia et al. Designing the stripe-ordered cuprate phase diagram through uniaxial-stress. Proceedings of the National Academy of Sciences, 121(1):e2303423120, 2024. [2] R. Khasanov, et.al., V. Sazgari, et al., and Z. Guguchia. Pressure-enhanced splitting of density wave transitions in La3Ni2O7−δ. Nature Physics, pages 1–7, 2025. [3] V. Sazgari, et.al., and Z. Guguchia. Pressure-induced enhancement of superfluid density in transition metal dichalcogenides with and without charge density wave. Phys Rev. Res. In Press, 2025. [4] V. Sazgari, et.al., and Z. Guguchia. Competing quantum orders in 6R-TaS2: Unconventional superconductivity, charge order, and an anomalous hall effect phase. arXiv:2503.13944, 2025. [5] SS. Islam, V. Sazgari, et al., and Z. Guguchia. Contrasting c-axis and in-plane uniaxial stress effects on superconductivity and stripe order in La1.885Ba0.115CuO4. arXiv preprint arXiv:2503.09236, 2025. [6] V. Sazgari, et al., and Z. Guguchia. The effect of in-plane uniaxial stress on superconductivity, structural transition, and stripe order in La2−xBaxCuO4. Under Preparation, 2025.

Links

• Seminars at the IFW

Last modified: Apr 16, 2025, 7:39:57 AM