Hall, Seebeck, and Nernst Coefficients of UnderdopedHgBa2CuO4+δ: Fermi-Surface Reconstruction in an Archetypal Cuprate Superconductor

Abstract

Charge-density-wave order has been observed in cuprate superconductors whose crystal structure breaks the square symmetry of the CuO 2 planes, such as orthorhombic YBa 2 Cu 3 O y (YBCO), but not so far in cuprates that preserve that symmetry, such as tetragonal HgBa 2 CuO 4þ (Hg1201). We have measured the Hall (R H ), Seebeck (S), and Nernst () coefficients of underdoped Hg1201 in magnetic fields large enough to suppress superconductivity. The high-field R H ðTÞ and SðTÞ are found to drop with decreasing temperature and become negative, as also observed in YBCO at comparable doping. In YBCO, the negative R H and S are signatures of a small electron pocket caused by Fermi-surface reconstruction, attributed to charge-density-wave modulations observed in the same range of doping and temperature. We deduce that a similar Fermi-surface reconstruction takes place in Hg1201, evidence that density-wave order exists in this material. A striking similarity is also found in the normal-state Nernst coefficient ðTÞ, further supporting this interpretation. Given the model nature of Hg1201, Fermi-surface reconstruction appears to be common to all hole-doped cuprates, suggesting that density-wave order is a fundamental property of these materials. There is a growing body of evidence that competing ordered states shape the phase diagram of the cuprates, and the identification of those states is currently a central challenge of high-temperature superconductivity. In the La 2 CuO 4 -based cuprates, whose maximal T c does not exceed 40 K, the existence of unidirectional densitywave order involving spin and charge modulations, known as stripe order [1,2] [9,10], a material with a maximal T c of 93 K, shows that its Fermi surface also undergoes a reconstruction [11,12]. Comparative measurements of the Seebeck coefficient in YBCO and Eu-LSCO reveal a detailed similarity [7,8], suggesting that Fermi-surface reconstruction (FSR) in YBCO is caused by some form of stripe order.Charge-density-wave modulations were recently detected in YBCO, via high-field nuclear magnetic resonance (NMR) [13] and x-ray-scattering [14][15][16][17][18] measurements, in the range of temperature and doping where FSR occurs [8,19]. Although the detailed structure of these modulations remains to be clarified, there is little doubt that they are responsible for the FSR in YBCO.The fundamental question, then, is whether such charge modulations are a generic property of the cuprates. Because both the low-temperature tetragonal structure of Eu-LSCO and the orthorhombic structure of YBCO distort the square CuO 2 planes and impose a preferred direction, charge modulations are perhaps triggered or stabilized by these particular forms of unidirectional distortion. To answer that question, we need to examine a cuprate material with square CuO 2 planes. For that purpose, the model material is HgBa 2 CuO 4þ (Hg1201), a tetragonal cuprate with the highest maximal T c of all single-layer cuprates (97 K) [20,21], in which no charge or spin modulations have yet been reported. ...

Large magnetothermopower and Fermi surface reconstruction inSb2Te2Se

“…Similar effects were also reported in several other materials such as high-T c cuprates, and was considered as a signal of the Fermi surface reconstruction. 46,47 For example, the high-field R H and S/T are found to drop with decreasing temperature and become negative in HgBa 2 CuO 4+δ , which is attributed to the charge-order wave and related Fermi surface reconstruction. 47 In similar materials Bi 2 Se 3 with high bulk carrier density, a strong variation of the chemical potential and Fermi energy above the quantum limit is observed and is believed to induce the observed increase in the Nernst response.…”

“…46,47 For example, the high-field R H and S/T are found to drop with decreasing temperature and become negative in HgBa 2 CuO 4+δ , which is attributed to the charge-order wave and related Fermi surface reconstruction. 47 In similar materials Bi 2 Se 3 with high bulk carrier density, a strong variation of the chemical potential and Fermi energy above the quantum limit is observed and is believed to induce the observed increase in the Nernst response. ? The change of the chemical potential could also happen in Sb 2 Te 2 Se and it could suppress the contribution of the states at the Necks of the Fermi surface to the Seebeck coefficient by suppressing the number of that states.…”

Emergence of charge order from the vortex state of a high-temperature superconductor

“…Despite the mounting evidence for a charge-ordering instability in virtually all cuprate families 2,6,[8][9][10][11]23,[26][27][28][29][30] , there is still a long way to go before elucidating the importance of this instability in determining the properties of the cuprates. Neither the possibility of an intertwining of the charge and superconducting order parameters 31 nor the possibility of a direct relationship between the two orders 32,33 can be addressed by the present results.…”

Ong construction for the reconstructed Fermi surface of underdoped cuprates

“…In addition to Y123, CDW modulations have also been reported for Hg1201 [43], Bi 2 Sr 2−x La x CuO 6+δ (Bi2201) [13] and La 2−x Sr x CuO 4 (LSCO) [44], suggesting that they are universal to hole-doped cuprates. Only in UD Hg1201, however, does R H (T ) become negative at low T and high B [10]. In Eu-doped LSCO, both spin and charge (stripe) order is stabilized (in zero field), and R H does again change sign at low T [45].…”

“…The observation of a sign change in R H , the thermopower S, and the Nernst coefficient ν in Y123 [7][8][9], Y124 [7], and HgBa 2 CuO 4 (Hg1201) [10] at low temperatures hinted that these pockets must result from Fermi surface reconstruction (FSR) induced by some form of (short-range) charge ordering that might itself be enhanced by the application of a high magnetic field, i.e., by the suppression of superconductivity. Biaxial charge order with wave vectors at (0, +δ) and (+δ, 0) (where δ is a fraction of the Brillouin zone coordinates) had already been apparent, in other cuprate families at least, in Fourier-transform scanning tunneling spectroscopy (FT-STS) [11,12] and later in resonant inelastic x-ray scattering (RIXS) [13,14].…”