Link between magnetic field-induced quantum criticality and phase formation in (original) (raw)

Magnetic-field-induced critical behavior in the hidden-order compound URu2Si2

Journal of Alloys and Compounds, 2004

We investigate the temperature and magnetic field dependences of the specific heat (C), magnetization and resistivity of URu 2 Si 2 from T ≈ 0.5 to 20 K in continuous and pulsed magnetic fields up to 45 T. The specific heat versus temperature at constant magnetic field shows that the transition at T 0 = 17 K is shifted to lower temperatures and sharpened when the magnetic field increases, and is completely suppressed at H ≈ 35.5 T. Between ∼36 and ∼39 T we observe a new first-order anomaly in the specific heat versus temperature. Above 40 T a Schottky-like contribution develops. We also find evidence of metamagnetism at H ≈ 38 T. In the close proximity of the metamagnetic transition we observe evidence of quantum critical behavior in the temperature dependence of the resistivity. We use our data to construct a revised (H,T) phase diagram for this fascinating compound. (M. Jaime).

Magnetic Field-Tuned Quantum Criticality in the Metallic Ruthenate Sr3Ru2O7

Science, 2001

The concept of quantum criticality is proving to be central to attempts to understand the physics of strongly correlated electrons. Here, we argue that observations on the itinerant metamagnet Sr 3 Ru 2 O 7 represent good evidence for a new class of quantum critical point, arising when the critical end point terminating a line of first-order transitions is depressed toward zero temperature. This is of interest both in its own right and because of the convenience of having a quantum critical point for which the tuning parameter is the magnetic field. The relationship between the resultant critical fluctuations and novel behavior very near the critical field is discussed.

Magnetic-field-induced quantum critical point in YbPtIn and YbPt_ {0.98} In single crystals

2006

A comprehensive transport study, as a function of both temperature and magnetic field in continuous magnetic fields up to 45 T reveals that URu2Si2 possesses all the essential hallmarks of quantum criticality at temperatures above 5.5 K and fields around 38 T, but then collapses into multiple low temperature phases in a hierarchically-organized phase diagram as the temperature is reduced. Although certain generic features of the phase diagram are very similar to those in the cuprates and heavy fermion superconductors, the existence of multiple ordered hysteretic phases near the fieldtuned quantum critical point is presently unique to URu2Si2. This finding suggests the existence of many competing order parameters separated by small energy difference in URu2Si2.

Quantum magnetism and criticality

Nature Physics, 2008

Magnetic insulators have proved to be fertile ground for studying new types of quantum many body states, and I survey recent experimental and theoretical examples. The insights and methods transfer also to novel superconducting and metallic states. Of particular interest are critical quantum states, sometimes found at quantum phase transitions, which have gapless excitations with no particle-or wave-like interpretation, and control a significant portion of the finite temperature phase diagram. Remarkably, their theory is connected to holographic descriptions of Hawking radiation from black holes.

Entropic topography associated with field-induced quantum criticality in a magnetic insulator DyVO4

Scientific Reports

Exploration of low temperature phase transitions associated with quantum critical point is one of the most mystifying fields of research which is under intensive focus in recent times. In this work, through comprehensive experimental evidences, we report the possibility of achieving quantum criticality in the neighborhood of a magnetic field-tuned tricritical point separating paramagnetic, antiferromagnetic and metamagnetic phases in a magnetic insulator, DyVO4. Magnetic susceptibility and heat capacity indicate to the presence of a long-range second order antiferromagnetic transition at TN ~ 3.2 K. Field variation of Magnetic susceptibility and heat capacity, along with differential magnetic susceptibility and DC field dependent AC susceptibility gives evidence of the modification of the antiferromagnetic structure below the tricritical point; implying the presence of a field-induced first order metamagnetic transition which persists down to 1.8 K. Further, the magnetic field depen...

Ferromagnetic Quantum Critical Endpoint in UCoAl

Journal of the Physical Society of Japan, 2011

Resistivity and magnetostriction measurements were performed at high magnetic fields and under pressure on UCoAl. At ambient pressure, the 1st order metamagnetic transition at H m ∼ 0.7 T from the paramagnetic ground state to the field-induced ferromagnetic state changes to a crossover at finite temperature T 0 ∼ 11 K. With increasing pressure, H m linearly increases, while T 0 decreases and is suppressed at the quantum critical endpoint (QCEP, P QCEP ∼ 1.5 GPa, H m ∼ 7 T). At higher pressure, the value of H m identified as a crossover continuously increases, while a new anomaly appears above P QCEP at higher field H * in resistivity measurements. The field dependence of the effective mass (m *) obtained by resistivity and specific heat measurements exhibits a step-like drop at H m at ambient pressure. With increasing pressure, it gradually changes into a peak structure and a sharp enhancement of m * is observed near the QCEP. Above P QCEP , the enhancement of m * is reduced, and a broad plateau is found between H m and H *. We compare our results on UCoAl with those of the ferromagnetic superconductor UGe 2 and the itinerant metamagnetic ruthenate Sr 3 Ru 2 O 7 .

Ferromagnetic quantum critical point in URhGe doped with Ru

Physical Review B, 2007

We have investigated the thermal, transport and magnetic properties of URh1−xRuxGe alloys near the critical concentration xcr = 0.38 for the suppression of ferromagnetic order. The Curie temperature vanishes linearly with x and the ordered moment m0 is suppressed in a continuous way. At xcr the specific heat varies as c ∼ T lnT , the γ-value c/T |0.5K is maximum and the temperature exponent of the resistivity ρ ∼ T n attains a minimum value n = 1.2. These observations provide evidence for a ferromagnetic quantum phase transition. Interestingly, the coefficient of thermal expansion and the Grüneisen parameter Γ remain finite at xcr (down to T = 1 K), which is at odds with recent scaling results for a metallic quantum critical point.