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SUMMARY:Modified Cu-charge density wave\, altermagnetic property and non-r
 eciprocal transport at manganite/cuprate interface  - Subhrangsu Sarkar\, 
 University of Fribourgo
DTSTART:20250414T101500Z
DTEND:20250414T110000Z
UID:TALK229984@talks.cam.ac.uk
CONTACT:Mads Fonager Hansen
DESCRIPTION:Single crystalline thin film heterostructures made of optimall
 y doped YBa2Cu3O7 and charge-orbital-ordered insulating Nd1-x(Ca1-ySry)xMn
 O3(NCSMO) exhibit a plethora of interesting and unusual physical propertie
 s. Using Resonant elastic and inelastic x-ray scattering (REXS/RIXS) in co
 njunction with x-ray linear and magnetic dichroism (XLD/XMCD)\, we measure
 d the systematic modification of orbital characteristics\, magnonic proper
 ties and charge density wave (CDW) in YBCO\, as a function of the hole dop
 ing and tolerance factor of the neighboring NCSMO layers.\n\nFor x=0.35\, 
 we observe a Cu-CDW order with the usual 𝑑𝑥2−𝑦2 orbital charact
 er at Q||=0.3 r.l.u\, which gets strongly enhanced as the tolerance factor
  of the manganite layers is decreased or when a strong magnetic field is a
 pplied [1]. On the other hand\, for x=0.5 and y=0.25\, we observe a comple
 tely new kind of Cu-order which has a small wave vector of Q||=0.1 r.l.u.\
 , a very large correlation length of about 40nm and a completely different
  𝑑𝑧2 orbital character [2].\n\nFurther\, for samples with x=0.35 and
  y=0.3\, we find an altermagnetic order that coexist with the above-mentio
 ned magnetically tunable charge density wave at the interface [3]. Cu-RIXS
  spectra and its polarization analysis indicate the presence of two separa
 te Cu-magnon modes corresponding to the bulk and the interface of YBCO. Wh
 ile the bulk mode disperses as usual as antiferromagnetic spin-fluctuation
 s in the 123-cuprate family\, the weakly dispersing interfacial mode exhib
 its a decreasing weight with increasing momentum transfer. This anomalous 
 magnon-behavior can be explained by a linear spin wave theory that takes i
 n to account a 2-D checkerboard-type orbital pattern of 𝑑𝑥2−𝑦2 
 and 𝑑3𝑧2−𝑟2 (as suggested from XLD)\, coupled with a spin-order
  leading to an altermagnetic property at the interface.\n\nFinally\, in si
 milar multilayers\, we observe below ~120K a spontaneous voltage (SpV) sig
 nal that can be used for driving a persistent current across an external c
 ircuit [4]. This SpV signal also exhibits an intriguing magnetic field dep
 endence with an overall strong suppression towards large magnetic fields a
 nd hysteretic\, jump-like changes at intermediate values of magnetic field
 . The mechanism underlying the SpV involves ambient electronic noise recti
 fication due to a ratchet-type electronic potential originating from a com
 peting coexistence of a nonpolar ferromagnetic (FM) minority phase and a c
 harge/orbital ordered (COO) majority phase with polar moments and charged 
 domain walls.\n\nReferences:[\n1] R. Gaina et al.\, Phys. Rev. B 104\, 174
 513 (2021). \n[2] R. Gaina et al. npj Quantum Mater. 6\, 12 (2021). \n[3] 
 S. Sarkar et al.\, PNAS Nexus 3 (2024)\, pgae100 \n[4] M. Soulier et al.\,
  Spontaneous voltage and persistent electric current from rectification of
  electronic noise in cuprate/manganite heterostructures\, under review
LOCATION:Mott Seminar Room (531)\, Cavendish Laboratory\, Department of Ph
 ysics
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