Abstract
At ambient pressure, CrAs undergoes a first-order transition into a double-helical magnetic state at TN=265 K, which is accompanied by a structural transition. The recent discovery of pressure-induced superconductivity in CrAs makes it important to clarify the nature of quantum phase transitions out of the coupled structural/helimagnetic order in this system. Here, we show, via neutron diffraction on the single-crystal CrAs under hydrostatic pressure (P), that the combined order is suppressed at Pc≈10 kbar, near which bulk superconductivity develops with a maximal transition temperature Tc≈2 K. We further show that the coupled order is also completely suppressed by phosphorus doping in CrAs1-xPx at a critical xc≈0.05, above which inelastic neutron scattering evidenced persistent antiferromagnetic correlations, providing a possible link between magnetism and superconductivity. In line with the presence of antiferromagnetic fluctuations near Pc(xc), the A coefficient of the quadratic temperature dependence of resistivity exhibits a dramatic enhancement as P (x) approaches Pc(xc), around which ρ(T) has a non-Fermi-liquid form. Accordingly, the electronic specific-heat coefficient of CrAs1-xPx peaks around xc. These properties provide clear evidence for quantum criticality, which we interpret as originating from a nearly second-order helimagnetic quantum phase transition that is concomitant with a first-order structural transition. Our findings in CrAs highlight the distinct characteristics of quantum criticality in bad metals, thereby bringing out new insights into the physics of unconventional superconductivity such as those occurring in the high-Tc iron pnictides.
| Original language | English |
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| Article number | 031017 |
| Journal | Physical Review X |
| Volume | 8 |
| Issue number | 3 |
| DOIs | |
| State | Published - Jul 20 2018 |
Funding
Work at IOP, CAS was supported by the National Science Foundation of China (Grants No. 11574377, No. 11025422, No. 11674375, No. 11634015); the National Key R&D Program of China (Grants No. 2018YFA0305700, No. 2014CB921500, No. 2015CB921303, and No. 2017YFA0302901); and the Strategic Priority Research Program and Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (Grants No. XDB07020100, No. XDB01020300, No. QYZDB-SSW-SLH013). Work at ISSP, UT was partially supported by a Grant-in-Aid for Scientific Research, KAKENHI (Grants No. 23340101, No. 252460135) and the JSPS fellowship for foreign researchers (Grant No. 12F02023). R. Y. was partially supported by the National Science Foundation of China (Grants No. 11374361, No. 11674392), and the National Program on Key Research Project (Grant No. 2016YFA0300504). Work at Rice University was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award No. DE-SC0018197, and the Robert A. Welch Foundation Grant No. C-1411. Research conducted at ORNL's High Flux Isotope Reactor and Spallation Neutron Source is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Synthesis of polycrystalline samples at ORNL was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Division of Materials Sciences and Engineering. This study was supported in part by the U.S.-Japan Cooperative Program on Neutron Scattering. We are grateful to Drs. Kazuki Komatsu (University of Tokyo) and Yoshihiko Yokoyama (IMR, Tohoku University) for use of the Zr-based amorphous pressure cell.
| Funders | Funder number |
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| U.S. Department of Energy |