arXiv subjects

K. G. Popov

Publications and source records attributed to K. G. Popov.

43 records · Page 3Linked to original sources

arXiv2008

Magnetoresistance of the heavy-fermion metal CeCoIn5

The magnetoresistance (MR) of CeCoIn5 is notably different from that expected for orbital MR due to the Lorentz force and described by Kohler's rule which holds in many conventional metals. We show that a pronounced crossover from negative to positive MR of CeCoIn5 that occurs at elevated temperatures is determined by the dependence of the effective mass M*(B,T) on both magnetic field B and temperature T. Thus, the crossover is regulated by the universal behavior of M*(B,T) observed in heavy-fermion metals. This behavior is exhibited by M*(B,T) when a strongly correlated electron system transits from the Landau Fermi liquid behavior induced by the application of magnetic field to the non-Fermi liquid behavior taking place at rising temperatures. Our calculations of MR are in good agreement with facts and reveal new scaling behavior of MR.

cond-mat.str-el↗

arXiv2008

Universal Behavior of Two-Dimensional 3He at Low Temperatures

On the example of two-dimensional (2D) 3He we demonstrate that the main universal features of its experimental temperature T - density x phase diagram [see M. Neumann, J. Nyéki, J. Saunders, Science 317, 1356 (2007)] look like those in the heavy-fermion metals. Our comprehensive theoretical analysis of experimental situation in 2D 3He allows us to propose a simple expression for effective mass M^*(T,x), describing all diverse experimental facts in 2D 3He in unified manner and demonstrating that the universal behavior of M^*(T,x) coincides with that observed in HF metals.

cond-mat.str-el↗

arXiv2007

Universal low-temperature behavior of the CePd_{1-x}Rh_x ferromagnet

The heavy-fermion metal CePd_{1-x}Rh_x evolves from ferromagnetism at x=0 to a non-magnetic state at some critical concentration x_c. Utilizing the quasiparticle picture and the concept of fermion condensation quantum phase transition (FCQPT), we address the question about non-Fermi liquid (NFL) behavior of ferromagnet CePd_{1-x}Rh_x and show that it coincides with that of both antiferromagnet YbRh_2(Si_{0.95}Ge_{0.05})_2 and paramagnet CeRu_2Si_2 and CeNi_2Ge_2. We conclude that the NFL behavior being independent of the peculiarities of specific alloy, is universal, while numerous quantum critical points assumed to be responsible for the NFL behavior of different HF metals can be well reduced to the only quantum critical point related to FCQPT.

cond-mat.str-el↗

arXiv2007

Universal behavior of $\rm CePd_{1-x}Rh_x$ Ferromagnet at Quantum Critical Point

The heavy-fermion metal $\rm CePd_{1-x}Rh_x$ can be tuned from ferromagnetism at $x=0$ to non-magnetic state at some critical concentration $x_c$. The non-Fermi liquid behavior (NFL) at $x\simeq x_c$ is recognized by power low dependence of the specific heat $C(T)$ given by the electronic contribution, magnetic susceptibility $χ(T)$ and volume expansion coefficient $α(T)$ at low temperatures: $C/T\proptoχ(T)\proptoα(T)/T\propto1/\sqrt{T}$. We also demonstrate that the behavior of normalized effective mass $M^*_N$ observed in $\rm CePd_{1-x}Rh_x$ at $x\simeq 0.8$ agrees with that of $M^*_N$ observed in paramagnetic $\rm CeRu_2Si_2$ and conclude that these alloys exhibit the universal NFL thermodynamic behavior at their quantum critical points. We show that the NFL behavior of $\rm CePd_{1-x}Rh_x$ can be accounted for within frameworks of quasiparticle picture and fermion condensation quantum phase transition, while this alloy exhibits a universal thermodynamic NFL behavior which is independent of the characteristic features of the given alloy such as its lattice structure, magnetic ground state, dimension etc.

cond-mat.str-el↗

arXiv2006

Asymmetric tunneling, Andreev reflection and dynamic conductance spectra in strongly correlated metals

Landau Fermi liquid theory predicts that the differential conductivity between metallic point and metal is a symmetric function of voltage bias V. This symmetry holds if the particle-hole symmetry is preserved. We show that the situation can be different when one of the two metals is a strongly correlated one whose electronic system can be represented by a heavy fermion liquid. When the heavy fermion liquid undergoes fermion condensation quantum phase transition, the particle-hole symmetry is violated making both the differential tunneling conductivity and dynamic conductance asymmetric as a function of applied voltage. This asymmetry can be observed when the strongly correlated metal is either normal or superconducting. We show that at small values of $V the asymmetric part of the dynamic conductance is a linear function of V and inversely proportional to the maximum value of the gap and does not depend on temperature provided that metal is superconducting, when it becomes normal the asymmetric part diminishes at elevated temperatures.

cond-mat.str-el↗

arXiv2005

Universal Cause of High-Tc Superconductivity and Anomalous Behavior of Heavy Fermion Metals

Unusual properties of strongly correlated liquid observed in the high-$T_c$ superconductors and heavy-fermion (HF) metals are determined by quantum phase transitions taking place at their critical points. Therefore, direct experimental studies of these transitions and critical points are of crucial importance for understanding the physics of high-$T_c$ superconductors and HF metals. In case of high-$T_c$ superconductors such direct experimental studies are absent since at low temperatures corresponding critical points are occupied by the superconductivity. Recent experimental data on the behavior of HF metals illuminate both the nature of these critical points and the nature of the phase transitions. We show that it is of crucial importance to simultaneously carry out studies of both the high-$T_c$ superconductivity and the anomalous behavior of HF metals. Our general consideration suggests that FCQPT and the emergence of novel quasiparticles near and behind FCQPT are distinctive features of strongly correlated substances such as the high-$T_c$ superconductors and HF metals. We show that the main properties and universal behavior of the high-$T_c$ superconductors and HF metals can be understood within the framework of presented here theory based on FCQPT. A large number of the experimental evidences in favor of the existence of FCQPT in high-$T_c$ superconductors and HF metals is presented.

cond-mat.str-el↗

arXiv2005

Hall coefficient in heavy fermion metals

Experimental studies of the antiferromagnetic (AF) heavy fermion metal $\rm YbRh_2Si_2$ in a magnetic field $B$ indicate the presence of a jump in the Hall coefficient at a magnetic-field tuned quantum state in the zero temperature limit. This quantum state occurs at $B\geq B_{c0}$ and induces the jump even though the change of the magnetic field at $B=B_{c0}$ is infinitesimal. We investigate this by using the model of heavy electron liquid with the fermion condensate. Within this model the jump takes place when the magnetic field reaches the critical value $B_{c0}$ at which the ordering temperature $T_N(B=B_{c0})$ of the AF transition vanishes. We show that at $B\to B_{c0}$, this second order AF phase transition becomes the first order one, making the corresponding quantum and thermal critical fluctuations vanish at the jump. At $T\to0$ and $B=B_{c0}$, the Grüneisen ratio as a function of temperature $T$ diverges. We demonstrate that both the divergence and the jump are determined by the specific low temperature behavior of the entropy $S(T)\propto S_0+a\sqrt{T}+bT$ with $S_0$, $a$ and $b$ are temperature independent constants.

cond-mat.str-el↗