Field-induced quantum critical route to a Fermi liquid in high-temperature superconductors

Abstract

In high-transition-temperature (Tc) superconductivity, charge doping is a natural tuning parameter that takes copper oxides from the antiferromagnet to the superconducting region. In the metallic state above T c, the standard Landau's Fermi-liquid theory of metals as typified by the temperature squared (T 2 ) dependence of resistivity appears to break down. Whether the origin of the non-Fermiliquid behavior is related to physics specific to the cuprates is a fundamental question still under debate. We uncover a transformation from the non-Fermi-liquid state to a standard Fermi-liquid state driven not by doping but by magnetic field in the overdoped high-T c superconductor Tl2Ba2CuO6؉x. From the c-axis resistivity measured up to 45 T, we show that the Fermi-liquid features appear above a sufficiently high field that decreases linearly with temperature and lands at a quantum critical point near the superconductivity's upper critical field-with the Fermi-liquid coefficient of the T 2 dependence showing a power-law diverging behavior on the approach to the critical point. This field-induced quantum criticality bears a striking resemblance to that in quasi-two-dimensional heavy-Fermion superconductors, suggesting a common underlying spin-related physics in these superconductors with strong electron correlations.quantum criticality ͉ strongly correlated electron materials ͉ superconductivity Q uantum criticality refers to a phase transition process between competing states of matter governed not by thermal but by quantum fluctuations demanded by Heisenberg's uncertainty principle (1). It has emerged at the front and center of the physics of strongly correlated electron systems known to host competing quantum orders, and is witnessed by a proliferation of reports on heavy Fermions (2-5), itinerant (quantum) magnets (6), and hightransition-temperature (high-T c ) superconductors (7), with quantum matter tuned (at times arguably) through a transition by pressure, magnetic field, or doping-arguably because one has to rely on long shadows cast by quantum criticality far above zero temperature (8), for, obviously, T ϭ 0 K cannot ever be attained.The often-invoked hallmark of quantum criticality is an unconventional behavior of resistivity. For resistivity contribution, the standard Fermi liquid (FL) theory of metals predicts a quadratic temperature dependence (T) ϭ (0) ϩ AT 2 at low temperatures. In high-T c cuprates, however, the baffling T-linear resistivity over a huge temperature range near optimal (hole) doping has been observed (9), flagging, in this sense, a nonFermi liquid (n-FL) behavior in the metallic state above T c . This has led to new theoretical concepts, some related [e.g., phenomenology of ''marginal Fermi liquid'' (10)] and some unrelated [e.g., ''strange metal'' state (11)] to quantum criticality. In most considerations of cuprates near quantum critical points (QCPs) the tuning parameter is charge doping (1, 10); and although there is some experimental support (7, 12) for a doping-driven QCP, it is still...

Fermi liquid behaviour in weakly disordered metals close to a quantum critical point

“…The same scaling A(a) ∝ a −2 was also found to fit data in La 2−x Ce x CuO 4 [7] with 2s = 0.38, in overdoped Tl 2 Ba 2 CuO 6+x [8] with 2s = 0.62, in CeAuSb 2 [9] with 2s = 1.0, and in YbAlB 4 [10] with 2s = 0.50.…”

“…Our work is motivated by a number of experiments on eight different materials [2][3][4][5][6][7][8][9][10][11][12], which display typical FL behaviour for appropriately low T . That is, quadratic in T resistivity and linear in T specific heat.…”

Magnetoresistance of Au films

“…Consequently, any deviation from the rule is viewed as anomalous transport behavior, with such violations often presented as evidence for non-Fermi liquid behavior of the metals. 1, 9 This common interpretation of the Kohler rule is not without objections. Lifetime anisotropy 10 or other more conventional transport mechanisms 11 have sometimes been invoked to explain violations of the Kohler rule.…”

Anisotropic breakdown of Fermi liquid quasiparticle excitations in overdoped La2−xSrxCuO4

“…The breakdown of this concept has therefore been studied in great detail by transport and thermodynamic measurements [2][3][4][5][6][7][8][9][10] . A common assumption is that the Fermi liquid self-energy ImS is local, that is, that it depends only on excitation energy o:…”