Motivated by the possibility of observing the co-existence between magnetism and unconventional superconductivity in heavy-fermion Ce$_{1-x}$Sm$_x$CoIn$_5$ alloys, we studied how the samarium substitution on the cerium site affects the magnetic field-tuned-quantum criticality of stoicheometric CeCoIn$_5$ by performing specific heat and resistivity measurements. By applying an external magnetic field, we have observed Fermi-liquid to non-Fermi-liquid crossovers in the temperature dependence of the electronic specific heat normalized by temperature and of the resistivity. We obtained the magnetic-field-induced quantum critical point (QCP) by extrapolating to zero temperature the temperature - magnetic field dependence at which the crossovers take place. Furthermore, a scaling analysis of the electronic specific heat is used to confirm the existence of the QCP. We have found that the magnitude of the magnetic-field-induced QCP decreases with increasing samarium concentration. Our analysis of heat capacity and resistivity data reveals a zero-field QCP for $x_\textrm{cr} \approx 0.15$, which falls inside the region where Sm ions antiferromagnetism and superconductivity co-exist.
Perfect $T$-linear resistivity associated with universal scattering rate: $1/τ=αk_B T/\hbar$ with $α\sim 1$, so-called Planckian metal state, has been observed in the normal state of a variety of strongly correlated superconductors close to a quantum critical point. However, the microscopic origin of this intriguing phenomena and its link to quantum criticality still remains an outstanding open problem. In this work, we observe the quantum-critical $T/B$-scaling of the Planckian metal state in the resistivity and heat capacity of heavy-electron superconductor Ce$_{1-x}$Nd$_x$CoIn$_5$ in magnet…
Nambu-Eliashberg theory for multi-scale quantum criticality : Application to ferromagnetic quantum criticality in the surface of three dimensional topological insulators
Time reversal invariant (TRI) topological superfluids (TSFs) and topological superconductors (TSCs) are robust symmetry protected gapped topological states. In this article, we study the evolution of these topological states in the presence of time reversal symmetry breaking (TRB) fields and/or sufficiently large TRI fields. Physically, one of the realizations of TRB fields can be internal spin exchange fields due to background magnetic ordering. We find that the fully gapped TSFs and TSCs are generically separated from other nodal states by various zero temperature quantum critical points tha…
Wide Quantum Critical Region of Valence Fluctuations: Origin of Robust Quantum Criticality in Quasicrystal Yb15Al34Au51 under Pressure
从理论上分析了重电子准晶Yb_（15）Al_（34）Au_（51）中强量子临界的产生机制。通过对含有Yb和Al-Au团簇的同心壳结构准晶及其近似晶体建立极小模型，我们发现Yb的一级价跃迁的量子临界点在基态相图中以点的形式出现.它们的临界区相互重叠，从而产生宽的量子临界区。这很好地解释了在Yb 15 Al 34 Au51中观察到的压力下的鲁棒临界性，并预测了在压力下的晶体近似物中的共同临界性的出现。在T-P相图中，准晶中的临界区比晶态近似体中的临界区宽，在T-H相图中，准晶中的临界区将出现场诱导的价键交叉“区”。
The mysterious universal line revealing an independence of spin fluctuation contributions to the heat capacity of (Mn,Co)Si on impurity contents and its nature is discovered. This situation probably declares an invariance of the spin subsystem energy that may provide by the response of itinerant electron system on the volume change at doping.
Motivated by recent experimental realizations of polar metals with broken inversion symmetry, we explore the emergence of strong correlations driven by criticality when the polar transition temperature is tuned to zero. Overcoming previously discussed challenges, we demonstrate a robust mechanism for coupling between the critical mode and electrons in multiband metals. We identify and characterize several novel interacting phases, including non-Fermi liquids, when band crossings are close to the Fermi level and present their experimental signatures for three generic types of band crossings.
The phenomenology of quantum phase transitions concerns physics at low temperatures and energies, and corresponding solid-state experiments often reach millikelvin temperatures. However, this is a scale where in many solids the influence of nuclear spins and their hyperfine interaction is no longer negligible. This may limit the observability of electronic quantum critical phenomena. Here we discuss how continuous magnetic quantum phase transitions get influenced, modified, or destroyed by the coupling to nuclear spins. We use simple yet paradigmatic spin models for magnetic quantum criticalit…
Field Driven Quantum Criticality in the Spinel Magnet ZnCr$_2$Se$_4$
我们报告详细的直流和交流磁化率，比热，和热导率测量的受抑磁体ZnCr $_2$ Se $_4$。在低温下，随着磁场的增加，这种尖晶石材料经历了一系列从螺旋自旋态到螺旋自旋态再到全极化态的自旋态转变。我们的结果表明从螺旋自旋态到全极化态存在直接的量子相变。当系统接近量子临界时，我们发现自旋的量子涨落具有非常规的$T^2$依赖的比热和与温度无关的热输运平均自由程等行为.我们完成了完整的相图ZnCr $_2$ Se $_4$下的外部磁场，并提出了挫折的量子临界扩展密度的临界模式的可能性，占不寻常的低能量激发附近的临界。我们的研究结果表明，ZnCr $_2$ Se $_4$是一个罕见的例子，三维磁体表现出非常规性能的场驱动量子临界。
The observation of quantum criticality in diverse classes of strongly correlated electron systems has been instrumental in establishing ordering principles, discovering new phases, and identifying the relevant degrees of freedom and interactions. At focus so far have been insulators and metals. Semimetals, which are of great current interest as candidate phases with nontrivial topology, are much less explored in experiments. Here we study the Kondo semimetal CeRu$_4$Sn$_6$ by magnetic susceptibility, specific heat, and inelastic neutron scattering experiments. The power-law divergence of the m…
