Anomalous Low-temperature Magnetotransport in Kagome Metal CsCr$_3$Sb$_5$ under Pressure

Abstract: As a unique kagome superconductor displaying clear signatures of strong electronic correlations, CsCr$_3$Sb$_5$ has drawn much attention. Its rich temperature-pressure phase diagram features intertwined orders including pressure-induced superconductivity and two density-wave-like phases, making it an outstanding platform to explore the complex coexistence and competition of multiple quantum orders. At around 30 K, which we designate as $T_3$, a possible anomaly manifesting as a hump in the resistivity has been observed, yet its nature remains largely unexplored due to limited supporting evidence from other probes. Here, we conducted systematic magnetotransport experiments under hydrostatic pressure to investigate the nature of this anomaly. Our results reveal an abundance of intriguing magnetotransport signatures below $T_3$, including a non-trivial temperature dependence of the Hall coefficient, multi-band characteristics, and pressure-enhanced anomalous-Hall-like effect. These signatures bear resemblance to those observed in the charge-density-wave state in the sister compound CsV$_3$Sb$_5$. These findings suggest the possibility of an additional, exotic electronic order in CsCr$_3$Sb$_5$, calling for further detailed investigations.

• The paper demonstrates that CsCr₃Sb₅ under pressure exhibits three distinct transport anomalies (T1, T2, T3) linked to unconventional electronic ordering.
• It employs hydrostatic pressure experiments, in-plane resistivity, Hall effect measurements, and mobility spectrum analysis to reveal multiband carrier dynamics.
• Enhanced AHLE and high-mobility carriers observed suggest novel quantum phases, potentially advancing the understanding of superconductivity and correlated states.

Anomalous Magnetotransport in Pressure-tuned CsCr$_3$Sb$_5$: Evidence for Exotic Electronic Order

Context: Kagome Lattice Physics and CsCr$_3$Sb$_5$

Kagome metals, featuring flat bands, Dirac points, and van Hove singularities, provide a fertile ground for emergent quantum orders and correlated phenomena. In the AV$_3$Sb$_5$ family, intertwined density waves, electronic nematicity, and superconductivity have been intensively scrutinized, with anomalous Hall-like effects (AHLE) frequently attributed to broken time-reversal symmetry or Berry curvature. The recently synthesized isostructural compound CsCr$_3$Sb$_5$ exhibits its Fermi energy near the flat band, distinguishing it from CsV$_3$Sb$_5$ (with Fermi energy near vHs) and underscoring its strong electronic correlations. The resulting phase diagram for CsCr$_5$0Sb$_5$1 is notably rich, with pressure-induced superconductivity, non-Fermi-liquid transport, and multiple density-wave transitions.

Experimental Approach and Magnetotransport Signatures

Single crystals of CsCr$_5$2Sb$_5$3 were subjected to hydrostatic pressures (5~kbar, 19~kbar) and magnetotransport was characterized via in-plane resistivity and Hall effect measurements across wide temperature and field ranges. Three distinct transport anomalies were observed: two density-wave-like transitions at $_5$4 and $_5$5, and a less understood resistivity hump at $_5$6~K.

Figure 1: Temperature dependence of resistivity, its derivative, and magnetoresistance (MR) for CsCr$_5$7Sb$_5$8 at 5~kbar and 19~kbar, showing anomalies at $_5$9, $_3$0, and $_3$1.

At 5~kbar, resistivity remains constant above 100~K but features a pronounced peak at $_3$2 and a well-resolved hump at $_3$3, with an inflection in $_3$4. MR increases sub-linearly with field and reaches 16% at 2~K. Pressure increase to 19~kbar shifts $_3$5 lower, introduces $_3$6, and preserves the hump at $_3$7. The low-temperature resistivity drops significantly ($_3$8 reduced by ~70%), and MR at 14~T grows to 230%, a 14-fold enhancement.

Hall Effect: Multiband Response and Anomalous Hall Features

Hall resistivity ($_3$9) exhibits temperature and field-dependent nonlinearities. Above $_5$0, $_5$1 is linear in $_5$2, and $_5$3 (Hall coefficient) becomes more negative with cooling, indicative of electron-like carriers. Cooling through $_5$4 and towards $_5$5 causes a sharp decrease and then a pronounced positive upturn in $_5$6, eventually crossing zero and becoming hole-like at lowest temperatures. Below $_5$7, $_5$8 develops pronounced nonlinerity and AHLE, which are strongly pressure-enhanced.

Figure 2: Hall resistivity vs. magnetic field and temperature dependence of $_5$9 at different pressures, highlighting a sharp upturn coincident with $_3$0, and comparison to CsV$_3$1Sb$_3$2.

The AHLE becomes particularly abrupt at 19~kbar, with stronger nonlinearity in $_3$3. Analogous signatures in CsV$_3$4Sb$_3$5 below its CDW transition suggest a possible link to density wave ordering. The AHLE onset correlates precisely with $_3$6, and its pressure dependence points to enhanced carrier mobility and multiband correlations.

Mobility Spectrum Analysis: Role of High-Mobility Carriers

To dissect the carrier contributions, mobility spectrum analysis (MSA) was employed on the magnetotransport data. The MSA reveals multiple carrier populations, with the high-pressure spectrum broadening and prominently featuring high-mobility carriers ($_3$7~cm$_3$8/Vs) below $_3$9. Warming attenuates these carriers and weakens the AHLE, reinforcing their association.

Figure 3: Extraction of nonlinear Hall components, comparison of Hall resistivity and conductivities, and mobility spectra at different pressures and temperatures, evidencing high-mobility carrier enhancement below $_5$0.

These findings mirror the re-interpretation of AHLE in CsV$_5$1Sb$_5$2 as arising from tiny Fermi pockets with ultra-high mobility, rather than intrinsic anomalous Hall physics alone.

Microscopic Origins and Competing Hypotheses

While the enhanced AHLE and transport mechanisms strongly implicate high-mobility carriers and multiband effects, several other origins are considered—altermagnetic order yielding internal fields and TRS breaking, kagome lattice loop currents, and nonzero Berry curvature from topologically significant band structures. The precise interplay among these remains unresolved, and multifaceted future experiments are warranted to untangle their respective contributions.

Implications and Future Directions

The anomalous transport properties below $_5$3 in CsCr$_5$4Sb$_5$5, especially under pressure, suggest the activation of exotic electronic orders and additional carrier channels with enhanced mobility. The robustness of $_5$6 against pressure, its synchronous manifestation in resistivity, Hall coefficient, and AHLE, and its close resemblance to density wave-related phenomena in AV$_5$7Sb$_5$8 identify it as a central feature of the correlated phase diagram. These results advance understanding of Kagome metals as platforms for quantum criticality, unconventional transport, and symmetry-broken phases—

potentially relevant for engineering emergent superconductivity or topological quantum states. Theoretical modeling and complementary spectroscopic probes (e.g., ARPES, NMR, STM) will be critical for distinguishing the microscopic mechanisms and their effects on the Fermi surface topology.

Conclusion

A systematic pressure-tuned magnetotransport study of CsCr$_5$9Sb$_3$0 reveals unprecedented anomalous low-temperature behaviors intimately tied to the $_3$1 anomaly. Enhanced AHLE, multiband response, and pressure-dependent high-mobility carrier spectra signal possible new electronic ordering. The linkage between $_3$2 and unconventional transport points to nontrivial carrier dynamics and further enriches the phase diagram of Kagome metals. Ongoing investigations are essential to fully elucidate the origins and implications of these phenomena for correlated quantum matter (2604.13553).