arXiv subjects

Shuzhang Chen

Publications and source records attributed to Shuzhang Chen.

5 recordsLinked to original sources

arXiv2026

Reaching Quantum Critical Point by Adding Non-magnetic Disorder in Single Crystals of Superconductor $(\text{Ca}_x\text{Sr}_{1-x})_3\text{Rh}_4\text{Sn}_{13}$

The Remeika series superconductor, $(\text{Ca}_x\text{Sr}_{1-x})_3\text{Rh}_4\text{Sn}_{13}$, shows a rare nonmagnetic quantum critical point (QCP) associated with the continuous charge-density wave (CDW) and structural transition under the ``dome'' of superconductivity achieved by tuning composition and applying pressure. Here we use a nonmagnetic point-like disorder induced by 2.5 MeV electron irradiation to suppress the CDW and drive the system to and even beyond the QCP. This conclusion is based on a clear evolution of temperature-dependent resistivity, $\rho\left(T\right)$, from the Fermi liquid to the non-Fermi liquid regime with increasing amount of disorder. Starting on the CDW side, below the suggested QCP concentration of $x_c=0.9$, added disorder resulted in a progressively larger linear term and a reduced quadratic term in $\rho\left(T\right)$. Nearly perfect $T-$linear dependence is observed at the dose at which long-range CDW order is suppressed to $T=$0, consistent with the expectations. We refine the QCP location in this system and place it in the interval between $x=$0.75 and 0.85. Our results strongly support the concept that the disorder can tune the system to the quantum critical regime and even beyond. It follows from the argument by Imry and Ma that any ordered phase is unstable toward quenched disorder. Introduced in a controlled way, this disorder becomes a novel non-thermal tuning parameter likely applicable to a variety of different systems.

cond-mat.supr-con↗

arXiv2024

Spin-orbit-splitting-driven nonlinear Hall effect in NbIrTe4

The Berry curvature dipole (BCD) serves as a one of the fundamental contributors to emergence of the nonlinear Hall effect (NLHE). Despite intense interest due to its potential for new technologies reaching beyond the quantum efficiency limit, the interplay between BCD and NLHE has been barely understood yet in the absence of a systematic study on the electronic band structure. Here, we report NLHE realized in NbIrTe4 that persists above room temperature coupled with a sign change in the Hall conductivity at 150 K. First-principles calculations combined with angle-resolved photoemission spectroscopy (ARPES) measurements show that BCD tuned by the partial occupancy of spin-orbit split bands via temperature is responsible for the temperature-dependent NLHE. Our findings highlight the correlation between BCD and the electronic band structure, providing a viable route to create and engineer the non-trivial Hall effect by tuning the geometric properties of quasiparticles in transition-metal chalcogen compounds.

cond-mat.mtrl-sci↗

arXiv2024

Reaching quantum critical point by adding nonmagnetic disorder in single crystals of (Ca$_{x}$Sr$_{1-x}$)$_{3}$Rh$_{4}$Sn$_{13}$ superconductor

The quasi-skutterudites (Ca$_{x}$Sr$_{1-x}$)$_{3}$(Rh, Ir)$_{4}$Sn$_{13}$ show a rare nonmagnetic quantum critical point associated with the second-order charge-density-wave (CDW) and structural distortion transition extended under the superconducting "dome". So far, the non-thermal tuning parameters for accessing the QCP included changing stoichiometry, pressure, and a magnetic field. Here we add another parameter -- a nonmagnetic point-like disorder induced by 2.5 MeV electron irradiation. The non-Fermi liquid regime was inferred from the analysis of the temperature-dependent resistivity, $\rho\left(T\right)$, in single crystals of (Ca$_{x}$Sr$_{1-x}$)$_{3}$Rh$_{4}$Sn$_{13}$. Starting at compositions below the known QCP concentration of $x_c=0.9$, added disorder resulted in a progressively larger linear term and a reduced quadratic term in $\rho\left(T\right)$. This behavior is supported by theoretical analysis based on the idea of superconducting fluctuations encompassing the crossover from quantum to thermal regimes. Our results strongly support the concept that the nonmagnetic disorder can drive the system toward the quantum critical regime.

cond-mat.supr-con↗

arXiv2024

Creep-enhanced vortex pinning revealed through nonmonotonic relaxation of the Campbell length

We study the effects of flux creep on the linear AC response of the vortex lattice in single crystals Ca$_3$Ir$_4$Sn$_{13}$ by measuring the Campbell penetration depth, $\lambda_{\rm \scriptscriptstyle C}(T,H,t)$. Thermal fluctuations release vortices from shallow pinning sites, only for them to become re-trapped by deeper potential wells, causing an initial increase of the effective Labusch parameter, which is proportional to the pinning well curvature. This effect cannot be detected in conventional magnetic relaxation measurements but is revealed by our observation of a nonmonotonic time evolution of $\lambda_{\rm \scriptscriptstyle C}(T,H,t)$, which directly probes the average curvature of the occupied pinning centers. The time evolution of $\lambda_{\rm \scriptscriptstyle C}(T,H,t)$ was measured at different temperatures in samples with different densities of pinning centers produced by electron irradiation. The curves can be collapsed together when plotted on a logarithmic time scale $t \to T\ln{(t/t_0)}$ confirming that the time evolution is driven by flux creep. The $\lambda_{\rm \scriptscriptstyle C}(T,H,t)$ is hysteretic with a noticeable nonmonotonic relaxation in the presence of a vortex density gradient (after zero-field cooling), but is monotonic after field cooling, where the vortex density is uniform. This result quantitatively corroborates the novel picture of vortex creep based on the strong pinning theory.

cond-mat.supr-con↗

arXiv2023

Robust superconductivity and the suppression of charge-density wave in $\text{Ca}_{3}(\text{Ir}_{1-x}\text{Rh}_{x})_{4}\text{Sn}_{13}$ single crystals at ambient pressure

Single crystals of Ca$_3$(Ir$_{1-x}$Rh$_x$)$_4$Sn$_{13}$ (3-4-13) were synthesized by flux growth and characterized by X-ray diffraction, EDX, magnetization, resistivity and radio frequency magnetic susceptibility tunnel diode resonator (TDR) techniques. Compositional variation of the Rh/Ir ratio was used to study the coexistence and competition between the charge density wave (CDW) and superconductivity. The superconducting transition temperature varies from approximately 7 K in pure Ir ($x=0$) to approximately 8.3 K in pure Rh ($x=1$). Temperature-dependent electrical resistivity reveals monotonic suppression of the CDW transition temperature, $T_{\text{CDW}}(x)$. The CDW starts in pure Ir, $x=0$, with $T_{\text{CDW}}\approx40$~K and extrapolates roughly linearly to zero at $x_c=0.58$ under the dome of superconductivity. Magnetization and transport measurements show a significant influence of CDW on the superconducting and normal state. Vortex pinning is substantially enhanced in the CDW region, and the resistivity is larger in this part of the phase diagram. The London penetration depth is attenuated exponentially upon cooling at low temperatures for all compositions, indicating a fully-gapped Fermi surface. We conclude that a novel $\text{Ca}_3(\text{Ir}_{1-x}\text{Rh}_x)_4\text{Sn}_{13}$ alloy with coexisting/competing CDW and superconductivity, is a good candidate to look for a composition-driven quantum critical point at ambient pressure.

cond-mat.supr-con↗